I have a 1999 Audi A6 and I always fill premium gas. I just wanted to know if I go with the regular gas then would it effect the mileage or performance of the car?
How much mileage should it give per gallon in city?

 

Yes, there was a video on youtube debating it. They concluded that with cars such as a Kia there is no difference, but in cars like the Evo or our 2.7t engines that there is a difference. If you go with regular gasoline I would imagine the engine would start to knock because the gas would ignite prematurely. I used the Middle grade, 89 I think, for 2 years in my 2.7t and never had a problem. Now I use 93 only because my car is chipped for added HorsePower and I generally get about 19 miles to the gallon in the city.

 

thats really good mileage for a 2.7... my 2.8 gets about 18 in town.