I just discovered that the EPA has 3 completely different sets of ratings for the last generation North American Chev/Geo Metro / Pontiac Firefly (1995-2000).
I have the same situation with my car! all 4 years are 5.0 liter PGMFI engines, with AOD transmissions. No mechanical changes, but check out my EPA's Highway mileage changes between 27, and 24!! That's like 11%
Interesting...I wonder if it has to do with any changing/stiffer emissions requirements. Maybe they changed the ECM programing.
They also could have seen the generous rating with the high EPA reported stats in the first place (compared to how the general public drove these-and what they actually got in MPG).
Interesting...I wonder if it has to do with any changing/stiffer emissions requirements. Maybe they changed the ECM programing.
They also could have seen the generous rating with the high EPA reported stats in the first place (compared to how the general public drove these-and what they actually got in MPG).
Let me know what you find out
That would make sense, seeing as they all go down in E.P.A. as the years go by.
The EPA periodically revises the way they calculate the gas mileage ratings. You can use them to compare cars of the same year, but not cars across different years. The way they calculate is very arbitrary and unscientific:
Look at the last paragraph. That's where they admit that they "adjust" the ratings downward to more closely match the real world. I read somewhere the adjustment is on the order of 20%. They also make up new rules sometimes like the air conditioner must be on, if equipped.
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