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99 Silverado MPG drop?!

99 Silverado MPG drop?!

Postby archerykid96 [OP] » Oct 09 2012, 6:52am

hey everyone! So before anyone wastes their time giving me heck for trying to improve MPG on a lifted truck...don't waste your time. I'll just delete your replies. I have a 99 silverado 1500 Z71 LS ext. cab (3 door) V8 5.3 with 3.73's. It's got a 6" RC lift on it with meaty 33's. My MPG on a good day is 11 in town and 12/13 highway. That seems strangely low to me. My family has always owned fords and my dad's 01 f150 gets 14/15 in town.. I'd kill for 14 in town right now. That just sounds heavenly. xD I know my MPG is never going to be great, it's a truck, we've always owned trucks, that's what I'm used to. But still, 11 in town seems really low for a 1500 even with a 6" lift and 33's. Does that sound normal to anyone else?? Or does it sound low? Is there anything I can do to improve it? That isn't SUPER costly.. Maybe getting it chipped by a shop? Will that help? How much will that run me? Any other ideas? I've heard conflicting reports about changing the exhaust or adding a CAI or something...even new spark plugs, though I don't see how that could change MPG. Anyway, any help is GREATLYYYY appreciated. Thanks y'all.
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Re: 99 Silverado MPG drop?!

Postby Onlyina_Chevy » Oct 09 2012, 7:24am

Let’s start out by saying that trucks (and all vehicles) are built by people with far more intelligence than you and I. They build them to specifications then make their assumptions on gas mileage on how people should drive in a ‘perfect’ world. I have heard of plenty of people getting the predicted gas mileage from trucks; I am not one of those people. I drive a 4WD with a V-8 like a 4WD with a V-8. I like to bury the speedometer when necessary (and if you ask the boys in blue, they’ll tell ya that I’m not lying).

Back to the intelligent people. They design the vehicles with specification in mind like drag and aerodynamics. Well trucks are huge blocks pushing wind. There are no aerodynamics, and drag can be modified (usually in a negative way) by as little as tire size. They figure for a certain width and height of a tire. Once you change either or both of these characteristics, you have changed the overall outcome of your drag, which in turn changes the overall ‘aerodynamics’. Not to mention the effect of the footprint on the road which adds more friction, thus creating even more drag.
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Re: 99 Silverado MPG drop?!

Postby camfire87 » Oct 09 2012, 8:06am

That mileage may be a little low, or it may be spot on. As was posted just before, changing aerodynamics on a truck makes a HUGE difference. Putting a 6" lift on means you have more exposed underneath your truck, which means more drag, and a greater amount of turbulence underneath the truck which in turn creates more drag again. You mentioned that you have meaty tires on, and that will cause a severe loss in economy. if you take two tires identical in size, but one with low rolling resistance and one with grippy mud treads, you can expect to see drastic differences in acceleration, handling, and economy.

If you haven't done so already, I for sure recommend doing a tune up, running some injector cleaner through, and making sure your air filter is good and clean.

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