Okay, this sounds drastic, but a few years ago I was talking to this guy who had a standard sedan style Toyota Yaris and swore he got 50+ mpg. He had punched a hole in some part of the engine (wish I could recall where) to let in more air, and although he lost power...he felt the increase in mpg was well worth it. Does this make sense to anyone? I'm leery to make a hole in my engine, but....but.....
Re: Punching a hole in your engine to increase MPG?
I put a 4" hole in the airbox of my truck, and blocked off the factory cool air intake to force the engine to suck warmer air from the engine bay. I really didn't see any gains on highway mileage, but seemed to help in city driving.
Re: Punching a hole in your engine to increase MPG?
If the engine was getting more air the ECU would just add more fuel to keep the air fuel ratio correct. The WAI is the only thing I can think of that he may have been talking about, but that wouldn't be giving the engine more air, just warm, less dense air.