Thread: in town fuel economy

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Have you checked your air filter

Something is wrong here-I have owned (or own) at least 7 of these Units (in either Yukon/Tahoe or Sierra Pickup) and, most of them before the 6 speed (I'll talk about those in a second)-

The pre-2008 models were all 4 speed Autos, and the worst Gas mileage I've seen was in a Tahoe that had 4.11 Gears (it was a terror around Town-not so much on the Hiway)-the best was with a Sierra (lighter, equipped with 3.42 Gears), and it got 22 mpg on the Hiway, and about 14-15 in Town (by the way, the only full-size GMC's that are AWD are Denali's)-

As far as the newer 6 speed models, they suck (as far as Gas!), especially if you live where I do (western US with lots of Mountains, Hills, and undulating terrain)-best mileage I have seen with the 6 Speed was 11 in Town and 16 Hiway (the eight speeds aren't any better)-

First off, do you have 3.42/3.73 or 4.11's in it? This made the single biggest change that I've seen (I've owned them all), and where/what kind of driving do you do?

I would agree that you have some kind of problem, as even with my '99-(first one-3.73 Gears), got about 20-21 Hiway, 12-13 in Town-do you tow a lot of loads? Are you getting this info from the Trip Computer or are you doing the math? Lots of variables here-

I never had a single Injector problem, as a matter of fact one of my friends bought my '06 (it has over 350,000 on it now) and no Injector problems-

I also noticed that Tires make a difference, and after trial and error I now only run Michelins (they can make up to a 2 mpg difference)-are you running the Stock size Tires (is it lifted)? I've put up to a 6" leveling/2" rear lift without issue-

You need to find a driveability guy who knows these Trucks/SUV's and have him give it the once over-has it had a Tune-up?