2007 Silverado Horrible Gas Mileage. - Chevrolet Forum

refinity02 · #1 09-03-2009, 08:59 AM

I have a 2007 Sivlardo 5.3 L, 2 wheel drive that is getting about 13 mpg. It may get about 14 on the highway but it usually stays about the same.
When I first bought the truck it would get 18 in the city and up to 24 mpg on the highway.
The dealer can not find anything wrong and there are no check engine lights on. Any one got any idea what to check. It really sucks filling the tank up every 260 miles. luke.pratt@navy.mil

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Mike Sigmond · #2 09-03-2009, 10:08 AM

Welcome to the forum! Does it have a good clean air filter?

refinity02 · #3 09-03-2009, 10:45 AM

Yes, I changed out the air filter from a stock one a to really good one. I run synthetic oil, new tires with correct air pressure and I have had the alignment checked. I have not changed the fuel filter yet. I have 23492 miles on the truck. It is driving me NUTS!

Mike Sigmond · #4 09-03-2009, 10:54 AM

Are the new tires bigger or smaller than the ones that were on it? What type of air filter do you have?

refinity02 · #5 09-03-2009, 11:05 AM

the tires are 265/70R17 they are the optional size. It came factory with 245's. The filter is a one you can get at any auto parts store, but it is more expensive then the cheap ones you can get. I have taken out numerous times to check it and I have vacuumed out the air box. the bad gas milage started before I got the new tires also.

Mike Sigmond · #6 09-03-2009, 11:17 AM

Ok, well lets see if anyone else here has any input, I take it its within the engine if you have a clean air filter and your tires are pretty much stock.

refinity02 · #7 09-03-2009, 11:46 AM

I am thinking something electrical to deal with fuel input sensoring but there is no check engine light. this truck is alwways broken, I should have called lemon on it when it was in the shop 18 times and a total of 41 days for the wiring harness when I first bought it.

bad2006z71 · #8 09-03-2009, 12:15 PM

your calcs are a little off due to the difference in tire size between 245's and 265's. its not much but you may actually be getting 14-15mpg instead of 13-14mpg.

also your gear ratio is now different due to the different sized tires. having a 2 wheel drive you may have a 3.23 ratio which is not good to move a heavy truck.

keep your tire pressure at recommended levels and get a tune by someone like blackbear performance and have them adjust your speedo for the new tires.

refinity02 · #9 09-03-2009, 12:29 PM

I have had the spedometer checked and it is dead on. The new tires only make the The tires are not larger in diameter just thicker. I asked the dealership and the tire deal that question. I have been having horrible gas milage way before I got new tires also.

Speedy650 · #10 09-03-2009, 05:35 PM

i highly doubt it, but maybe a leak?