The thermal efficency of an engine is pretty static when its built, thus it can be as efficient as it can given the ideal conditions (right AFR producing the hp they want), the milage will be dictated by the amount of fuel flowing into the engine which is controlled by your foot. Youll have an easier time regulating gas milage with your foot, than remapping and retarding the engine.

Completely unrelated threadjack, but every time I see your avatar I >HAVE< to say it out loud in Bane's voice. :bellyroll::bellyroll::bellyroll::bellyroll:

You can get a 10-20% improvement altering the factory ECU. With direct injection, you can run some absurdly lean mixtures like the lean burn motors from the 80's did (think 16+ AFRs).

But they definitely would be less than ideal for emissions, so you won't find it from an OEM. Probably not the best for the catalytic converter either.

But yes, it can be done. We toyed with it for quite some time and found about a 15% improvement on pump and e85. While legalities prevent us from offering this, if you're using a DIY platform, you should be able to extract several more MPG with the right approach.

By experimenting through trial and error, I've found some differences between stage 2 OFT tunes. My A/R header is only slightly unequal in length, see pic, and so I've tried tunes for both EL, and UEL headers. There are significant differences between UEL and EL header tunes. I'll show you 2 of them, see pics below. My average MPG with the version 2.062 stage 2 91 Octane EL OFT tune was only 28, yet my average for the version 2.062 stage 2 91 Octane UEL OFT tune is 30, and the pics show the reason why. the exhaust isn't opened as far, or as early with the UEL tune versus the EL tune. I've found that the EL tune is quick, but wasteful, while the UEL tune is slower, but more torquey in the low revs, and more fuel-efficient. I think the VVT, (AVCS), is where to start experimenting for better mileage, also delay the ramp up in the drive-by-wire tables to keep your foot from wasting as much fuel.:coolpics: I removed the proprietary pictures of the VVT tables, but you can check them yourself by opening them in RomRaider.

thanks everyone for the comments Ill definitely look into them.