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GMC Forum: Getting better gas mileage on my Suburban ?
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Old 04-03-2011, 06:38 PM
Beaucefus Beaucefus is offline
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Join Date: Nov 2010
Posts: 4
Default Getting better gas mileage on my Suburban ?

I have a 1999 GMC 2500 5.7L gasoline powered suburban.
Even with the smaller engine this thing is quite the gas guzzler. I haven't had it very long and am strongly thinking I made a mistake in buying it. I should have held out for a diesel. I almost bought a 7.4L but my friend said I would get better mileage with the 5.7L. Well I don't see it. It cost a small fortune to fill it up at $3.59 a gallon. I put in $80.00 yesterday I barely got just over a half a tank. I haven't figured out the mileage yet but I'm guessing it's probably around 9-11 miles per gallon. I took the 3rd row seat out to make it lighter. I didn't think this would do a whole lot but every bit helps. I would like some suggestion from others what they have done to make their suburbans more fuel efficient, or even if it's possible at all. I thought of putting a flowmaster on it.
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Old 05-01-2011, 10:17 AM
KatieCow KatieCow is offline
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Join Date: May 2011
Posts: 1
Default Suburban gas mileage

I have a 98 5.7 2x4 with 200k on it and I get 15-19mpg. 2x4 is lighter but I put a K&N cold air intake, flowmaster super 40 and the power is way better. It sounds beefy and I got 12-17 mpg before I did those 2 things. Total it cost me about $600. The KN cold air intake cost way more than just the filter but you get triple the performance. Most stock intake have the truck sucking air thru a straw. Im going to get a trottle body spacer, new spark plug and wires and maybe a new computer and see how that works. I know its pricy but its way better than getting a new truck with car payments. Oh by the way for everybody E85 is 85 octane so yea you would get less mileage but its a sustainable cheaper gas supply and its thicker so dont use it if your going to the snow.
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Old 05-01-2011, 07:59 PM
happy 2011 happy 2011 is offline
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Join Date: Apr 2011
Location: new hampshire
Posts: 540

e85 is not 85 octane goggle it
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Old 06-06-2011, 12:52 PM
Bert97 Bert97 is offline
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Join Date: Jun 2011
Posts: 3
Default Fuel Economy

Alright, first thing first: weight is the main enemy to fuel economy. You were right to remove your 3rd row, as it saves about 80 pounds. Next, remove all of the things in the back that you don't need. The 3rd row mats, for example, weigh about 10 or 15 pounds and you don't need them with no 3rd row. Then maybe even remove the 2nd row mats, and if you're really committed, the front mats as well. All together, they weigh something like 30 pounds. And then the big one: the fuel itself. With a 42-gallon tank, and 8 pounds per gallon, the fuel weighs in at just about 340 pounds. Driving around with a full tank wastes fuel carting around the rest of the fuel. I only ever put mine up to about half a tank and add some at about 1/8 of a tank.
After the weight saving, it's time to adjust your driving style. Accelerate slowly, don't rush up to a red light just to stop again. Try braking very early and coasting up to the light without stopping at all. If you can maintain even 5mph, you'll save about 20% of the fuel you would use accelerating from 0 to cursing speed.
The A/C is a fuel-mileage killer too, so to the extent that you can, limit your use of it. At high speeds, the windows should be up and I usually drive at about 55 or 60 in the right lane with my driver's side mirror folded in to reduce drag. I am kind of crazy and I also removed my radio antenna, but I still clearly pick up my favorite stations.
Next, be sure your tires are inflated properly. You'd be surprised how many people have under inflated tires, something that can affect your mileage by between 5 and 6%. Get them up to right near the maximum pressure.
I've been doing these things with my 1997 GMC Suburban 4x4 and I've been getting about 20 mpg, though that is about 65% highway driving.
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