View Full Version : G8/GT stock - gas mileage update - how about others?

May 9th, 2011, 15:39
On our mother's day trip to my son's house and back I tested the mpg for the round trip of just over 120 miles. Going to his house the mpg was a flat 28, primarily cruising at 65mph and relied on cruise control as much as possible. This is on interstate for approx. 75% of the distance, then 55 mph or less for the rest of the trip. The return trip netted 24.2mpg. This was due to having some stop and go running around while in the area of my son's house to go out and eat. So the overall mpg was about 26. I don't think that was too bad for this vehicle. The terrain here in the Atlanta GA area is mixed up and down hills and inclines on the interstates as well as the surface streets. I have clocked as much as 28.7 mpg on a trip to Florida (more than 550 miles one way). This was by using the old "fill-the-tank-at-the-start" and "fill-the-tank-at-the-end", then calculate the mpg, not relying on the DIC reading (which in my car happens to be quite close - within 1 mpg or so).
The car now has almost 34000 miles and still performs flawlessly - a real pleasure to drive.
Anyone else having similar experiences?

June 1st, 2011, 17:05
Seems pretty good. About the same mileage as the GTO(05,06), maybe a little better. Different heads and camshaft along with tunung are the main difference in ponies from the same block. In my 2004 GTO at 70 mph in 6th gear I am at about 1900 RPM's. The 292 gear in the G8 should make for some lower RPM's than the 346 does in the GTO.i Makes for some good gas mileage. I just cant get myself to drive in 6th gear for some reason.

Big Injun Dave
September 11th, 2012, 14:18
I have found that my best highway mileage occurs when I place the automatic trans in manual 6 and run at 70-75 mph. I also have noted, the maximum economy occurs when using premium fuel.

November 24th, 2012, 07:40
A recent round trip from Atlanta GA area to central Florida netted an overall mpg of 27.3. This is by fill-up and calculate method, not the DIC reading (although it is usually quite close, + or -. MY G8/GT now has just over 49k miles. I try to keep 35-36 psi tire pressure all around - cold - and have found this to work best for me.

Anyone else with an update?