This Just In... All 2008's must run PREMIUM!

[blackhawk29]

Originally Posted by H2 007

Have the same slight rough idle at times as others have mentioned. Have been using Shell 87 since day one. Just filled up today and got 13.6 MPG, city driving, with 1050 miles on it.

On the highway, if I set the cruise to 65MPH, I can get a solid 16 - 17 MPG. Driving around rural roads at 40-45MPH and I have seen 18+ MPG.

Of course this is all with very conservative driving.

No knocks, pings or anything else for that matter.

Overall, I think this new engine / trans / gearing is great.

for what it matters my 08' f-450 twin turbo idles smoother than my 08 H2. Sounds like most 08's have a rough idle. at a stop light the other day, the engine idled up by itself kinda lurched forward, if i did not have the brakes firmly on it would have ended up in the back of someones car. i think gm has something messed up with the ECM fuel mapping and they need to issue a reflash update. My idle is so rough that it almost feels like its going to stall out, i can watch a bottle of water jump all over the place in my cupholder. I can also feel it through the brake pedal. I'm all for the exhaust note and hot cam, but can't we have that with a vehicle that idles properly?