I didn't really notice a mpg difference. If I were to make a guess, my tune which leans the car out at idle and part throttle more than likely offset the mileage that may have been lost by switching gears. For an all factory car, I'd would guess I would have lost 3-4 mpg, but I'm not building my car for fuel mileage

 

what I ment was the site I went to that had the specs said the cars were governed to 110 an theoretically they will do 155mph ,mine has 150mph speedo ,I found the info at www.automobile-catalog.com then type in search 1995 Camaro z28 ,then scroll down ,its all there,all you need is about a good 2 mile stretch an we got a few of those around ,to take a car up to top speed