I have a 2007 Grand Prix 3800 series V6 with a super charger and 117,000 miles on it. I've never had a super charger and have a couple of questions.


Will gas mpg go down with a super charged engine? If the answer is no, then will mpg go down if the super charger is not working correctly?


Why the drastic difference in mpg when using regular as opposed to premium?


if I use regular gas I'll only get about 20 or less mpg but if I use premium I'll get maybe 24, is this normal?


NADA says I should get 28 and its no where close.

Supercharged engines particularly these ones, have bigger fuel injectors than the N/A engines. Thus, they will naturally consume more fuel. Technically, yes, if you were to remove the serpentine belt from the supercharger you would get slightly better fuel economy. There have been a few people here that noticed their belt broke and they never knew it. This is achieved by the PCM seeing less air volume via the mass air flow sensor and cuts back on the fuel delivery.

As far as the type of fuel, the higher octane fuel only prevents pre-detonation in your engine due to hotter than normal air because of the supercharger. I can only think that your engine is pulling back on timing because its seeing more KR with regular fuel vs the higher octane fuel.


You might be seeing the N/A 3800 specs for fuel consumption.

Agree with Mike......

But don't drive it with regular......detonation due to higher compression temps will cause problems....

Always loved these engines....

If you just got this vehicle, and don't know it'* maintenance history, I would change the SC'er fluid....it uses special fluid for the SC'er, which basically is a synthetic oil....

Standard issue Mobil 1 Synthetic 5W-30 oil can be used instead of the expensive GM stuff

https://www.gmforum.com/normal-maint...ut-oil-278817/