Thread: Mpg
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Old 03-08-2008, 05:09 AM   #9
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Re: Mpg

It depends on the chip/tuning. Most factory programming keeps things a bit on the rich side. The drawback is a bit higher HC emissions, but the benefits are lower NOx emissions and less chance of detonation when John Q Idiot tries to tow too much weight or forgets to flush his radiator. Some power and fuel economy can be gained by leaning out the mixture on some vehicles, but its neglegible. I didn't gain any when I leaned out mine. I picked up 10 hp, but it didn't do anything at the pump. Some cars show a noticable increase, but its tiny.

Most generic performance "chips" also advance the timing which requires the use of premium fuel... which completely negates any money savings you might have gained from any increase in MPG.
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