Are you sure you don't mean "Engine Air Filter"? A dirty engine filter will degrade ICE performance. A dirty cabin air filter will just mean less airflow in the cabin! At the very least, just pull the cabin air filter, it takes all of 20 seconds, tap it out over a trash can, better yet, just buy several, keep them where ever you like, and replace the filter yourself as needed! The same applies to the ICE filter, about a 2 minute swap out process!
The gen 2 oil wants to be 2/3rd's up the dipstick for maximum mileage, but on a road trip I wouldn't take the chance of burning oil, the tire pressure can effect the overall mpg's, if it's 32 vs 42 pounds, is per chance your emergency brake dragging, how dirty is your interior cabin filter, and how dirty is your ice filter. 37-42 mpg's at 70+mph is good, better then any other car on the road, a TDI might give it a run. Read more: http://priuschat.com/threads/gas-mileage-bad-on-long-trips-why.129222/#ixzz2iaXaXR8h Follow us: @PriusChat on Twitter | PriusChat on Facebook
I was trying to copy and paste a reply by "URSLE" but I couldn't do it. He mentioned that the cabin air filter and the ice filter must be clean to help with mpg.......I just looked again and that was his statement!
I'd set it aside as a misstatement. Contrary to popular mythology, a dirty engine air filter should have very little or no impact on MPG of a traditional Otto-cycle gasoline engine. It will cut the available engine power, which is the performance that racers care about. But people who care about MPG are not 'flooring it', thus not fully removing the air flow restriction caused by the throttle plate, so some air flow restriction from a dirty filter doesn't matter. Lack of sufficient power should appear long before any MPG problem. This is not necessarily true for an Atkinson-cycle engine, which tends to run with a more wide open throttle. But I haven't seen sufficient discussion to understand how much MPG a Prius may actually lose to a dirty filter. While 'everybody knows it', I haven't seen anyone quantify it.
I will agree with ICE filter, cabin air, not so much! At the risk of stretching the imagination, you could say the fact the cabin filter is dirty it will impede the flow of air and thus make the fan motor run harder thus increasing current draw to try to compensate. The amount of power wasted there is so small he wasted more energy mentioning it than your car actually suffers! At least tap it out if dirty!
I suppose, if the cabin air filter were dirty enough to restrict airflow, that the heating and cooling efficiency would be compromised, and the engine would have to work harder to compensate. It may not be obvious, but I don't think it's impossible.
