Facts You Should Know About Air Filters
We believe the primary
function of an air filter is to deliver both high airflow and superior dirt
protection. We design our air filters to
provide minimum restriction allowing high airflow into an engine. In the vast majority of cases
increased airflow will increase engine performance measured by horsepower and
throttle response (torque). The performance benefits of maximum
airflow are clear, compelling and well documented. That is why so many
professional racers are willing to run expensive vehicles with no air filter, as
opposed to installing a disposable air filter. They are seeking the
additional horsepower and throttle response needed to win the race.
We design our air filters to provide superior filtration of the contaminants
that can harm your engine while maximizing the airflow characteristics of the
filter in question. The ability of an air filter to protect your engine is
generally measured in accordance with testing procedure ISO 5011. We subject a sample of our filter designs to this test procedure
using Coarse Test Dust, which includes particles ranging in size from less than
5.5 microns to 176 microns. As a point of reference, a human hair is
approximately 50 microns in diameter. The result of the above test
procedure is a specific air filtration efficiency number. This efficiency
number represents the percentage of test dust retained by the filter and thereby
kept out of an engine. Our goal is to design our air filters to
achieve maximum airflow while targeting overall filtration efficiency at
Because no two air
filters are alike, the specific airflow and overall filtration efficiency will
vary depending on the filter in question. However, you can rest assured
that each air filter we sell, has been designed to achieve high air flow while
providing superior filtration.
Both air flow and dirt
protection are critical to engine performance. For this reason a consumer
should always evaluate an air filter based on both its filtration efficiency and
air flow capabilities. It is very easy to design an air filter that exhibits
high airflow simply by reducing its filtration to unacceptable levels. As
the “look” of a K&N air filter has become popular, many companies have
begun offering products that copy that “look.” While imitation is said to be
the sincerest form of flattery, our own testing has shown that many of these
look-alike products do not provide a safe level of engine protection.
What’s the Big Deal About Air Flow?
put, Everything! At its most basic level, an engine is an air pump. More
air entering the engine increases the efficiency of the combustion process
creating more horsepower and torque. Horsepower is a measure of the engine's
maximum power while torque measures how quickly you can accelerate.
K&N Filtercharger? is designed to increase engine performance in
both horsepower and throttle response by reducing air flow restriction.
Maintaining optimal, unrestricted air
flow becomes a problem when it must pass through a filtering medium. The level
of air resistance varies depending on the size, surface area and physical
attributes of the filtering medium.
A Word About Filtration Requirements
There are few areas more confusing than identifying dirt
retention requirements when it comes to air filters. Most vehicle
owner’s manuals remain silent on the point. In fact, few air filter
manufacturers publish any information as to the filtration efficiency of their
filters. This stands in marked contrast to oil and fuel filters where
there is a relatively large amount of information regarding filtration
requirements and capabilities. Studies have shown most engine wear is
caused by particles 10 to 20 microns in size. K&N air filters, like
most quality disposable air filters, provide excellent filtration of these
To ensure our air filters
provide a high level of dirt protection, we regularly test our air filter
designs using the testing procedure described above. Those tests demonstrate
K&N air filters generally achieve overall filtration efficiency in the range
of 96% - 99%. The fact that our air filters at times reach overall filtration
efficiencies as high as 99% while maintaining high airflow is a testament to the
quality and capabilities of our oil impregnated cotton air filter medium.
occasion we see “new” air filter media’s developed and sold under the
premise they provide increased levels of dirt filtration. More often than
not, as opposed to quoting specific efficiency numbers, this “increased
protection” is described as increased dirt retention capacity, meaning the
filter can hold more dirt before requiring replacement. Remember, K&N
air filters have always provided a service life in excess of disposable filters
and then only require cleaning and oiling for re-use.
We encourage customers to do their
homework and be aware of the filtration capabilities of an air filter before
they buy. Our own testing has revealed wide differences in filtering
capabilities. We were surprised to see some disposable paper air filters
with an overall filtration efficiency as low as 93%. We hope we have
provided enough information to ensure consumers know what they are getting when
they buy a K&N air filter.
Filtration 101 - A Deeper Cut
Most people believe that all air filters
function on a go/no go basis where dirt particles that are larger than the
openings in the filter media are trapped while particles that are smaller than
the openings can pass right through. A dry paper air filter does function in
this manner. That’s why paper filters are so restrictive to air flow. The
openings in this type of filter have to be very small to filter efficiently.
The oiled cotton media used in the
K&N air filter functions in an entirely different manner. There are scientific principles that determine how an air filter removes dirt particles
from the air stream. The first of these principles is known as interception,
which applies to dirt particles traveling with the air stream. Air flow will
always take the shortest path and as the air is forced to flow around the
filter’s fibers some of the particles will contact the sides of the fibers and
be captured. These particles are then held in place by the oil or tacking agent
in the fiber.
Another principle is known as impaction,
which mostly affects larger or heavier dirt particles. Impaction occurs when the
inertia or momentum of the particle causes it to deviate from the flow path. In
other words the heavy particles do not follow the air stream around the
filter’s fibers but instead they run straight into the fibers and are
The most important principle for our use
is diffusion, which deals with the laws of physics that govern the motion of
very small dirt particles. Small particles are highly affected by the forces in
the air stream. Forces such as velocity changes, pressure changes, turbulence
caused by other particles and interaction with the air molecules cause these
very small particles to become random and chaotic. As a result, these particles
do not follow the air stream and their erratic motion causes them to collide
with the filter’s fibers. This phenomenon enables an air filter to
capture dirt particles that are much smaller than the openings in the media.
In addition, the way that dirt collects
or loads on the K&N filter is very different. A paper filter exhibits
"surface loading" which means dust collects only on the surface of the
media. In contrast, K&N filters exhibit "depth loading". The
multiple layers of cotton fibers provide many levels of dust retention. This characteristic allows the K&N
filter to hold significantly more dirt per square inch of media than the average
paper filter. Utilizing these scientific principles,
K&N has been able to design an air filter that is very free flowing while
also being highly efficient at removing dirt from the air.
Independent Laboratory Test Results
In order to verify our filters maintain filtration levels
necessary to protect your engine, we test our filtering media through
independent laboratories. The testing procedure used in the past was the SAE
J726 air filter test procedure established by the Society of Automotive
Engineers, however this procedure was recently superseded by
testing procedure ISO 5011.
We have included a detailed example of test results using
the SAE J726 procedure. These results are for two individual air filters
that each demonstrated among the highest overall filtration level we have
achieved with our media.
Lab Flat Filter Test Results - Click Here!
Lab Round Filter Test Results - Click Here!
Paper vs K&N
To meet minimum filtration
standards, paper air filters must be thick and/or the fibers must be tightly compressed
and dense. Therefore paper elements that provide adequate filtration are more restrictive to air flow by design.
Additionally, as a
paper filter becomes more and more clogged, the pressure inside the filter drops
while the atmospheric air pressure (approximately 14.7 psia at sea level)
outside the filter remains the same. It’s like using your lungs to draw the
air out of a plastic milk bottle. When the pressure differential becomes too
great, the bottle will collapse. The same thing could happen to your paper
filter, although it is unlikely. But what will happen could be just as severe.
An excessively high pressure differential created by a restricted filter can
literally pull dirt particles through the paper medium. In other words, the
performance of a paper filter, i.e. air flow through the filter and its ability
to protect your engine, DECREASES near the end of its service interval.
- Pleated wood pulp bonded
- As dirt builds, passages
are plugged and filter must be replaced in approximately 10,000 miles.
- Irregular passages filter
out dirt on a go/no go basis.
- As fibers swell from moisture
or oil blow-by vacuum pressure increases and airflow decreases.
- Turbulent filtered air.
|Typical Foam Air
- Lack of surface area
hinders air flow and dirt holding capacity. Open cell foam usually
saturated with oil.
- Dirt builds on outside
and blocks the openings.
- Higher vacuum pressures
distort the cells drawing dirt deeper into the filter.
- Airflow is reduced as
cells become blocked.
- Turbulent filtered air.
The K&N air filter is somewhat more
complex. The unique design features multiple layers of oiled cotton fabric which
captures the airborne dirt particles. These dirt particles cling to the fibers of
the filter and actually become part of the filtering media. This process, known
as depth loading, allows the K&N air filter to retain significantly more dirt
per square inch than a paper filter. The cotton fabric is sandwiched between
pleated aluminum screen. Pleating increases surface area which in turn prolongs service intervals. Pleating exposes
substantially more surface area compared to a flat element like foam.
The dirt particles collected on the
surface of a K&N element have little effect on air flow during much of
its service life because there
are no small holes to clog. Particles are stopped by layers of crisscrossed
cotton fibers and held in suspension by the oil. As the filter begins to collect
debris, an additional form of filter action begins to take place because air
must first pass through the dirt particles trapped on the surface. That
means a K&N air filter continues to exhibit high air flow throughout the
life of the filter while it is accumulating dirt. At the same time, the
air flow for an average paper air filter can decrease dramatically as the paper
element gets dirty. So as dirt accumulates, the performance advantages of
a K&N air filter can increase! Tests performed by an independent
laboratory commonly known as the Frazier Permeability Test have shown that the
Medium used in K&N air filters flows more than 300% more air than paper air
filter medium when compared on a square inch per square inch basis. A Square
inch comparison is not directly proportional to the increase you can expect from
installing a K&N air filter in replacement of a paper air filter due to the
effect of such things as filter size, number and depth of pleats. However, you
can be assured a K&N air filter will provide dramatically more air flow which can enhance engine performance.
Disposable Filter Life
Stop Throwing Away Your
One K&N air filter will last the life of your vehicle.
Assuming you drive your vehicle 150,000 miles and bought and installed a
disposable filter every 15,000 miles, you would throw away 10 disposable
Washable and Reusable
All of our air filters are washable and reusable.
They can be easily cleaned and oiled using our K&N Recharger kits as many times
as reasonably necessary. In our testing laboratory, we have washed and
re-oiled one K&N Air Filter more than 100 times and it still performed up to
specification. We recommend you check your air filter every 30,000 miles,
however, under most street conditions the filter will not require cleaning until
50,000 miles of continuous use. And yes, we’ve heard the stories of customers
who ran their K&N filter for 100,000 miles without a cleaning, but we believe
cleaning after 50,000 miles to be the most beneficial service life without
sacrificing air flow.
Stock Replacement Filters
We manufacture stock replacement air
filters to fit most vehicles on the road today. These filters are designed to
replace the factory air filter that came with your car. They fit into the
factory air box and are engineered to seal tightly with no air leakage. These
filters are made with the same filter media used in our racing filters and put a
little bit of performance into your every day driving experience. Our stock
replacement filters are backed by our Million Mile Limited Warranty and are
emissions legal in all 50 states.
Our stock replacement air filters are
washable, reusable and can handle all driving conditions. Water will not damage
their performance and with proper cleaning, they will last the life of your
engine. And of course, they offer high air flow and that means performance!
Our replacement air filters are designed
to provide up to a 4% increase in horsepower and torque. The amount of
performance gain varies from vehicle to vehicle based on the overall factory air
intake design. The greater the restriction created by the stock paper element,
the greater the potential performance gain when you switch to a K&N.
The airflow comparison charts below are
for two individual stock replacement air filters sold by K&N. The
tests were performed in a dust-free environment on laboratory equipment. Flow
comparison results will vary depending on part number, vehicle application and
barometric air pressure. For a complete description of the air flow testing
method used by K&N to develop the information in the charts below and other
published air flow results, see the section on this web site “K&N
Air Flow Testing.”
Beyond the Stock Air Filter and Air Box
Addressing the next area of
restriction, K&N engineers looked at the vehicle’s air box (the container
that houses the air filter) and any hoses or duct work connecting it to the
engine. Because the air must first travel through this system before it reaches
the carburetor or throttle body, the overall size and shape of the system has a
profound effect on air flow. Air, like water, does not like to
turn corners nor does it react favorably when confronted by an obstruction such
as a sharp bend in a hose or a baffle. In many cases, the air box and/or the
hoses and duct work used to create the air filtration system is just as
restrictive as the original paper filter element. In some extreme cases, the air
box and/or the air delivery system is the greatest source of restriction. The
inlet to the air box is a good example. In many instances this opening is one
half the cross sectional area of the throttle body or carburetor opening. It
would be like trying to run a marathon while breathing through a soda straw.
cylindrical air cleaner box covering a throttle body or carburetor is another
example. Most often, these round air cleaner housings are sealed to the outside
air. The engine must then breathe through a snorkel attached to the perimeter of
the housing. At times the snorkel is fed through a network of hoses and scoops.
To directly address the problem, we
introduced a line of air intake kits, the most popular of which is our Fuel Injection Performance Kits (better know by the
acronym, FIPK). These kits replace both the air box and the restriction. Our FIPKs
vary in design because they are application specific meaning each kit is
engineered to fit a particular make, model and year of vehicle. FIPKS
utilize a 360-degree filter design which provides increased surface area to
promote air flow.
Off-Road and Racing Off-Road
An air filter element becomes an
insurance policy when used in off-road applications. Competitors will sacrifice
a high-tech engine for a chance to win a race — but to win, they must finish.
If the engine ingests too much dirt and debris, it may die an ugly death before
the vehicle can cross the finish line.
You might think this would be the
perfect application for an inexpensive, throw-away paper filter. But remember,
in competition a little extra horsepower can mean the difference between coming
in first or finishing second. The air filter now becomes an important part of
the performance package.
K&N air filters are designed to
provide minimum restriction long after disposable air filters have begun choking
an engine. In
other words, due to its characteristics, the restriction of a K&N replacement
filter increases at a slower rate when compared to a disposable filter, i.e. a K&N
filter will last longer under the same conditions. That's why most
off-road competitors choose K&N filters.
hypothetical 24-hour off-road race to further the point, a properly sized
K&N filter will see the racer through to the end with cfm to spare. The
equivalent disposable air filter, on the other hand, will need to be replaced with a
fresh element to ensure the engine has an adequate supply of air to complete the
course. A K&N will provide
excellent filtration without sacrificing air flow for a longer period of time —
that’s performance with value.
One might consider a paved road course
or oval track as a clean air zone. After all, how much dirt and debris could be
hovering above an asphalt track?
Subscribing to that theory, a road racer
may elect to forgo an air filter in favor of large volumes of unrestricted air.
However, testing the theory using an air filter enclosed in a vented housing
should dispel the myth. The filter and housing will trap particles of loose
trash kicked up by other race cars during the heat of battle. Dirt, small stones
and pieces of shredded rubber expelled from soft compound racing tires can be
found inside the housing after even a short race. Once a driver, car owner or
engine builder realizes just how much trash is thrown around during a normal
race, few would expose their expensive engines to unfiltered air in future
Whenever possible, performance enthusiasts should install a K&N 360 degree
open-element filter. A correctly sized conical or round filter will deliver virtually
unrestricted air flow. And, as we have learned,
providing the engine with all of the air it needs promotes optimum performance.
In a high speed application, a K&N filter will straighten the air which
Straight cut velocity stacks, for example, pose a unique
problem. Exposed to the outside air, velocity stacks experience a phenomena that
actually hinders performance at high speed. We are referring to stacks and air
horns that protrude through the hood and extend into the air stream so the
direction of the air rushing over the car is at a perpendicular angle to the
length of the tube.
Air moving rapidly over these stacks
create turbulence inside the opening. At high speed, the rushing air tends to
create a partial vacuum inside the tube. The condition is counterproductive to
air flow. The phenomena also effects open carburetors. The higher the ground
speed, the greater the problem. Vacuum created by the engine is trying to coax
air into the cylinders and the high speed air flowing over the open end of the
stack is causing resistance.
Reversion creates other problems. In an
automotive application, reversion refers to reversed air flow, or in simpler
terms, it’s when air in the intake runner reverses direction for a split
second. The condition is caused when a burst of pressure escapes into the intake
runner from the cylinder during valve overlap.
resonance shock waves inside the tubes which exit the open end of the tube at
various rates depending on engine speed. It has also been proven that these
shock waves interfere with each other when the stacks are in close proximity.
Installing a free-flowing air filter on
top of each stack or over the carburetor air horn eliminates these conditions.
How? The solution is simply explained. The filter creates a plenum over the
opening. Air entering the filter is slowed, smoothed and straightened. The
filter then becomes an endless source of calm, clean air. Shock waves dissipate
within the confines of the plenum without interfering with the shock waves
emitted from an adjacent stack.
A Better Choice For The Environment
K&N cotton air filters have always been washable and reusable, designed for the life
of an engine. If you assume an engine life of 150,000 miles in which a
disposable air filter must be replaced every 15,000 miles, only one K&N air
filter would be used during the same period in which 10 disposable air
filters were discarded. Considering there are millions of vehicles throughout
the world, the volume of disposable air filters that could be eliminated from our
landfills is a staggering number.
If maximum horsepower is the objective,
the size and shape of the air filter element is paramount.
Let's first consider shape. When fitting a conventional round filter on top of the engine, such as a carburetor,
central fuel injection or throttle body fuel injection, we have found a large
diameter, short filter will flow more air than a small diameter, tall filter.
For example, a 10-inch diameter filter 2-inches tall will flow more air than
a 5-inch diameter filter that is 4-inches tall. Where space permits, the height
of the filter should be between 1/5 and 1/4 of its diameter.
The shape of the filter is less
important if the application calls for a remote mounted filter, which includes
many late model fuel injected models. Typically these vehicles will use a flat
panel filter or a conical or cylindrical shaped filter with a rubber mounting
flange designed to be mounted on the end of the inlet hose.
That brings us to size.
Use the formula below to compute the minimum
size filter required for your particular application. The usable portion of
the filter is called the EFFECTIVE FILTERING AREA which is determined by multiplying
the diameter of the filter times Pi (3.1416) times the height of the air filter
in inches, then subtracting .75-inch. We subtract .75-inch to compensate for
the rubber seals on each end of the element and the filter material near them
since very little air flows through this area.
| A = effective filtering area
CID = cubic inch displacement
RPM = revolutions per minute at maximum power
|Example: A 350 CID Chevy engine with a horsepower peak at 5,500 rpm.
If you are sizing a panel filter,
multiply the width of the filter area (not the rubber seal) times its length.
If you are sizing a round filter, use the following formula to determine the
height of the filter.
| A = effective filtering area
H = height
D = outside diameter of the filter
3.14 = pi
0.75 = the rubber end caps
Referencing the K&N catalog shows the proper filter for this application would be an E-1500 which
is 3.5 inches tall. Keep in mind, this is the minimum size requirement. To extend
the service interval and to provide an even greater volume of air to the engine,
install the largest filter that will fit in the space allotted. If the space
above the engine is restrictive, perhaps a remote filter arrangement could be
used to gain space.
Off-road conditions require added
filter area. A filter should be sized 1-1/2 to 2 times larger than normal for
any conditions that could be considered severe. In this case, the E-1500 used
in our example should be replaced by an E-1120 or an E-1150. For long distance
off-road events, two double-size remote mounted filters would be best.
Some important tips about K&N Filterchargers
K&N Filtercharger is a high-performance air
filter, both in terms of air flow and filtration. However, the service interval
can vary widely depending on the severity of the driving conditions. The service
interval can be from 100 miles in a desert-racing environment to 50,000
miles for normal street use. The proper way to determine when an air filter
needs service is with an air restriction gauge. Such a device is commonly used
on heavy duty trucks and construction equipment. A restriction gauge, measures
the pressure differential inside and outside the filter and gives the
information in different forms of measurement. As the filter collects more and
more dirt, the restriction value increases. At a predetermined point or rate of
restriction, the filter is serviced. The maximum allowable restriction for a
K&N Filtercharger is 15" of vacuum (water). If the restriction is
allowed to go higher, the filter media might become so restricted that the
element could distort allowing dirty air to bypass the filter and enter the
engine. Conversely, cleaning a filter too often will shorten its serviceable
life expectancy. Installing a restriction gauge will optimize service intervals
and take the guess work out of your maintenance schedule.
K&N air filters are washable and reusable.
They are easily cleaned and oiled using a K&N Recharger kit. They can
be cleaned and oiled as many times as reasonably necessary. In our testing
laboratory, we have washed and re-oiled a K&N Air Filter more than 100 times and
it still performed up to specification.
All K&N stock replacement air
filters are backed by our famous million mile limited warranty.
See our warranty page for stock replacement and off-road warranty
When servicing a K&N filter, take
care not to over-oil the element. Besides impeding air flow, excess oil
can migrate into the intake system where it can coat electronic sensors, which
some OEM’s claim may hinder the sensors’ operation and result in a repair
that will not be covered under warranty. Although K&N disagrees with
such claims, as explained in more detail on this web
site, in order to avoid a dispute with an OEM over the denial of a warranty
claim, we suggest that you be careful not to over-oil your K&N air filter.
Never saturate the filter. If oil drips from the filter,
wash it and start over. Use only K&N oil. For example, an E-1500 filter has
92.4-inches of surface area requiring 1.707 fluid ounces of oil. Follow oiling
instructions included with your filter or refer to the instructions listed
Fit and Finish
When installing a K&N filter, check
all gaskets, clamps and seams for damage and/or deterioration. Check the filter's
sealing surface. Do not install a filter if the seal shows signs of damage or
deterioration. Check for cracks in the air box, particularly at the seams and
around the corners. Such defects could cause air leakage around the filter.
Also, check to insure the filter is sealing properly in the air box. A plastic
air box can warp from age or continuous heat cycling. Apply a thin layer of
filter grease on both sides of the seal each time the filter is installed. An
impression in the grease will indicate a positive seal. Check any lines or hoses
connected to the air box or adjoining hoses leading to the engine.
Engine oil in the air box, resulting
from excessive blow-by, will cause the filter to shrink and possibly lose its
seal. Clean any dust or debris out of the air box with a damp cloth, making
sure nothing enters the air inlet while the filter is out. Never start the engine
without the filter in place. Use only K&N Air Filter Recharger® to clean your filter.
Harsh household cleaners can damage the cotton material and/or the rubber seal.
Check the outside of the medium for broken wires, rips or tears. Do not use
an element that shows signs of damage or wear. Use K&N Air Filter Sealing Grease
on the sealing surface that contacts the air box. Do not use sealing grease
on clamp-on type filters. If a filter is especially difficult to install, it
will come with an instruction sheet explaining the correct installation procedure.
Keep the instruction sheet with the vehicle for reference anytime the filter
is removed. It is very important the filter be installed correctly. The filter
can be positioned in the base or the lid, whichever is more convenient and makes
the installation easier. Do not use excessive force to install a filter.
Contrary to what you may have heard
or read, in the USA, a K&N Filtercharger will not void your vehicle warranty. The Magnuson-Moss
Warranty Act, passed in 1975, prohibits a manufacturer from conditioning its
warranty of a consumer product upon the consumer using any article or service
(other than one provided without charge under the warranty) which is identified
by brand, trade or corporate name, unless expressly authorized by the Federal
Trade Commission. If the manufacturer does not provide air filters
free of charge, they cannot void the vehicle's warranty simply because you have
installed an aftermarket air filter.
Letter from K&N Regarding Vehicle Warranty and K&N Replacement Filters
We offer thousands of stock replacement
applications, hundreds of universal clamp-on filters and dozens of Fuel
Injection Performance Kits. Our goal is to provide the highest quality component
at a competitive price. A K&N Filtercharger will be the last filter you will
ever buy for your car, truck, motorhome, motorcycle, ATV, boat or jet ski -
Emission Warranties on New Vehicles
THE MYTH: A manufacturer's
new-vehicle warranty is automatically voided once an aftermarket part (non-original
equipment) is installed.
THE TRUTH: Rarely does the
use of aftermarket parts violate a new-vehicle warranty.
THE RULES: Federal law, (the
Clean Air Act), requires two emissions warranties: a "defect" warranty and a
"Defect" warranties require the
vehicle manufacturer to produce a vehicle which, at time of sale, is free of
defects that prevent it from meeting required emissions levels for its useful
life, as defined in the law.
"Performance" warranties require
that vehicle manufacturer make repairs - at no cost to the owner - should a vehicle fail to meet certain levels of emissions performance during the
warranty period. This period ranges from 2 years (or 24,000 miles) to 5 years
(or 50,000 miles) for most parts, and up to 8 years (or 80,000 miles) for certain emission-controlled
parts, specifically, the catalytic converter, the electronics emission-control
unit and the on-board diagnostic device (check
owner's manual for specifics on your vehicle).
Consumers are protected under a
parts self-certification program administered by the Environmental Protection
If a parts maker self-certifies
it's parts under this program, the vehicle manufacturer cannot void the emissions
warranty even if the certified part fails and/or is directly responsible for
the emissions warranty claim. In this situation, the vehicle manufacturer must
arrange a settlement with the parts manufacturer, but the new vehicle warranty
is not voided under the law.
If a parts maker chooses not to
self-certify it's parts, the only case where a vehicle manufacturer can void
the emissions warranty is if a non-certified aftermarket part is proven to be
responsible for an emissions claim.