SAE/US Dept of Energy shocker: changing your ride's air filter doesn't do squat for fuel economy

That old saw about clogged air filters killing fuel economy simply doesn't apply with modern fuel injected computer controlled gasoline engines, or with modern diesels, although it DOES still apply to old school engines with traditional carburetors.

Gasoline engines were tested in THIS STUDY.

...Results reveal insignificant fuel economy and emissions sensitivity of modern vehicles to air filter condition, but measureable effects on the 1972 vehicle. All vehicles experienced a measured acceleration performance penalty with clogged intake air filters.

Diesel engines were tested in THIS STUDY.

...The two sedans did show a modest loss in acceleration performance due to filter clogging, showing measurable effects at WOT conditions.

For consumer advice, the authors conclude that changing the air filter more often than the vehicle manufacturer's recommendation will be of little or no value (driving
conditions should be taken into account and are normally discussed in the vehicle owner's manual)...

My own actual experience with my 98' Jetta TDI mirrors the DOE results. My intake manifold was severely clogged with carbon crud from the EGR system a while ago dramatically restricting air flow, yet the car would still get in the 45-50mpg range as it always had. However cleaning the crap out of the intake manifold improved acceleration performance quite visibly.

So, it would seem that unless you're unhappy with a modern ride's acceleration performance, you're wasting money doing frequent air filter changes.

Gotta give DOE Oak Ridge props for some truth telling here that ordinary people can use out in the field to save a few bucks.

posted by Purp at 05:21 PM

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