Delbert51

Hello everyone. I'm a long time Chevrolet / GM driver (my father worked at GM for 30 years) but a first time writer to this site. I purchased a 2011 Silverado 1500 in September to replace a 2003 Silverado 1500 and absolutely love it except for the gas mileage. The truck obviously has active fuel management which I assumed would result in an upgrade in MPG over my previous Chevy Silverados (I also owned a 2000 Silverado 1500 before the 2003 unit). So far, however, the gas mileage is actually worse. The sticker notes to expect 21 MPG highway (with a range of 17-25 MPG) and 15 MPG city (with a range of 12-18 MPG). I am getting nowhere close to that fuel efficiency. I am getting around 10 MPG in city driving and 14 1/2 MPG on the highway. I thought maybe this was the engine just breaking in but I don't think that is the case any longer.

I took a trip from Cleveland to Buffalo a few weeks ago, which was my first extended highway driving with the vehicle. I was burning normal 87 octane unleaded gasoline (not E85). In almost 100% highway driving (no jackrabbit starting and stopping), the truck got 14.1 MPG on the way to Buffalo and 14.2 MPG on the way back to Cleveland. On the way back to Cleveland, I had the DIC on the screen showing instantaneous fuel mileage and if the engine was in V8 or V4. I had the cruise control set at 73 miles per hour. I had nothing in tow and had no additional cargo in the truck (besides my wife!). Besides stopping at the tool booth on I90 when you exit NY and go into PA, I only had one other instance where I had to take off the cruise control. I watched the DIC for about 100 miles like this from Buffalo to Erie, PA (all while traveling on I90) and the only time the engine went into V4 was the two times I took off the cruise control (traffic was extremely light during my drive). It was in V8 the rest of the time and showed an instantaneous MPG anywhere from 12 to 18 MPG based on whether I was traveling on flat road (which is most of that drive) or on a slight incline or decline. I assume that this can't possibly be correct since the active fuel management (I would think) should drop the engine into V4 when driving at just above posted speed limits on flat interstate. I took the truck into the dealer to check and they tell me that everything is working properly - they completed diagnostics and took it for a short test drive. The truck does go into V4 and shows instantaneous 99 MPG if I'm at interstate speeds and turn off the cruise control or completely let off the gas.

Has anyone else purchased a 2011 Silverado 1500 4WD crew cab and checked their gas mileage results? If so, I would appreciate it if you could please let me know if you are seeing similar results to mine or if you are getting fuel consumption at close to the sticker estimates. If anyone has any other ideas on why this might be occurring I would appreciate hearing them as well. Or is it just normal for the truck to never go into V4 when on an interstate on flat terrain if you have the cruise control set above some speed less than the 73 I was traveling? I am o.k. with around 15 MPG on the highway if that is what I wind up getting - I didn't buy the truck to worry about gas mileage (it's not my primary vehicle for daily transportation and I'll wind up using it most of the time to lug around my trailer and four wheeler). However, if this is all that I (or anyone with a similar vehicle) should expect, it would be better for GM to let customers know that up front. If my results are not typical, I'd like to know that as well so I can take the next step and contact GM directly to see how to proceed. Thanks for your help.

greyhound

I have a 2010 silverado 1500 crew cab 4x4 with a 6.0 litre motor [flex fuel]. The dealer gave me a free tank of gas [regular], it ran smooth but it didn`t last long. Common sense tells me a V8 wants premium gas and the manual recomends a top tier gas. My average MPG is 16.8 to 17, half highway and half around town, in the foothills of NC next to Virginia. Premium gas burns cleaner, cooler and produces more HP and better MPG. This motor has the same HP my 05 corvette had. Would you put regular gas in a vette?

tsduke

Common sense tells me the opposite. The book calls for 87 octane. Why do you say premium gas burns cooler and with better mpg? I would say it actually burns hotter and with worse gas mileage. The size of the motor does not dictate the need for premium fuel. Your wasting your money on premium IMHO.

Here's a car talk Q&A on premium fuel. Covers the mpg and cleaner question.

http://www.cartalk.com/content/featu...ium/myths.html

greyhound

Here`s the math-26 gal. x 3.00 for regular= 78.00, 26gal x 3.20 for premium=83.20, a difference of 5.20 per tankful. He`s getting 14 mpg now and should be getting at least 17mpg, a difference of 3mpg. 26 gal x 3 more mpg is 78 miles. 78 miles divided by 17mpg is 4.6 gal. at 3.00 for regular is 13.80. So you`re actually saving 8.60 per tankful using premium. Even Click and Clack say theres a slight increase[ In their opinion]. Bottom line here is try it and see before taking advise from an entertainment show with alot of guessing.

tsduke

Sorry, I don't understand your math. To say their actually a savings of $8.60 per tankful is a very very large assumptions. You are assuming 91 fuel will get him from 14mpg to 17mpg. No way that's gonna happen(I will eat my words if shown evidence otherwise). Click and Clack's "myth" answer also said the increase would be so slight you won't notice the difference, your talking 3mpg here.

Yes, Car Talk is a entertainment show on top of answering car quesitons, but they do provide good car knowledge. They also aren't just a couple a grease monkeys. Both Tom and Ray are MIT graduates.

tsduke

To the OP, how many miles on your truck now?

in2pro

1.The most likely reason Delbert51 mpg was low was his 73mph speed, most MPG is calculated at a speed of about 45mph.

2.Top tier has nothing to do with octane but the detergents and other additives added to the fuel.

3.Higher octane fuel only prevents pre-detonation or knock due to high compression or advanced timing.

using anything other then what is recommend for fuel is a waste of money UNLESS you have done engine mods that require higher octane related to statement #3 above.

tsduke

I think I can see a larger improvement using 87 w/o ethanol vs with than I do between any 87 and 91, which is still offered in Iowa thankfully. Ethanol is all politics and don't belong in my gas tank.

nauticstar87

I know of a few mods to up your fuel mileage if you want. I went from 11mpg to 15mpg in my 2500HD with the 6.0 and 4.10 gears. Cost me around 700 bucks all together though. A CAI, exhaust, and a Blackbear Performance Tune well worth the money.

wellmax

what differential does your truck have???

they did make some with 3.73 and 4.10
if your truck has one of these lower ratio differentials it will not get the mileage of a truck with the 3.42 or 3.23 ratio.

also might try to find a station in your area that sell non-ethanol gas, if you can, try a few tanks and see if the mileage goes up.

however, my friends new Camero with 6.2 motor and fuel management system locks up on 4 cylinder mode during interstate driving, he gets in the low twenty's, but when he want to go that thing will kick butt.