Getting better MPG with the 5.3L

NewfZ · May 7, 2006

Hey, I'm planning on buying a 1999-2001 GMC Sierra Ext. Cab 5.3L(2WD, Auto) once I graduate. I was wondering what ways can I achieve better MPG. I know keeping the RPMs under 2.5k help. I've heard warmer weather also make the 5.3L a bit better on gas too. I would also like to know of any MPG AND power increasing mods. I'm told headers, a less restrictive exhaust, intake, throttle body spacer, e-fan, tuner all do that. I'm curious what else people can suggest. I'm planning on not keeping the truck stock, but at the same time I'll be doing a lot of highway driving for road trips me and my friends like to do. Anything you guys can suggest would help.

BTW: I'm also considering to do a 2'' body lift and 32'' tires. But I know that'll bring my MPG down, I'm just curious by how much. I'm told the 2WD Sierras ride quite low compared to the 4x4's. Thanks.

- Andrew

silveradoHO · May 8, 2006

A good custom tune can give you both more power and better mileage.

They can also adjust your speedo for your larger tires. Cold air intake and exhaust are also good. Throttle body spacers are a waste of time. The lift should not affect you too much, 2'' is not really any higher than a stock Z71.

NewfZ · May 8, 2006

A good custom tune can give you both more power and better mileage.
They can also adjust your speedo for your larger tires. Cold air intake and exhaust are also good. Throttle body spacers are a waste of time. The lift should not affect you too much, 2'' is not really any higher than a stock Z71.

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Well I'd like to add some height and bigness to my truck without losing too much MPG. I know not to expect good MPG out of a fullsize truck, but at the same time. I'd like to achieve the best possible MPG out of it at the same time. What sized tires would somoene suggest, just something to make the truck ride higher and more firmer without causing too much loss in the MPG?

And can you suggest any good 87' octane tunes I can use? I was thinking a Superchips tuner for the 5.3.

fossil · May 8, 2006

If you're concerned about gas mileage, don't mess with it. You ain't gonna make it get any better,and in any case probably make it worse if you start modding it.

Also my advice, go for the 4x4. You spend a little more, gas mileage is the same on them now-a-days, and they hold their retail value a whole lot more than a 2 wheel drive model, as I found out when I sold mine. More demand for 4x4's.

Mine gets a solid 25.6 mpg per Imp gal (21.3mpg/us gal) at 108kph (68mph) on the highway. And 19.4mpg/imp gal (16.2mpg/us gal) city driving. At 108kph on the highway the tach runs at 2100rpm. If I drive faster than 110kph mpg drops significantly.

I've got a 05 Z-71, 5.3L/auto/4.10 gears/17 inch tires/all stock, no mods, and power is more than adequate. It actually took a Ford Mustang GT off the line at a red light the other day.

NewfZ · May 8, 2006

If you're concerned about gas mileage, don't mess with it. You ain't gonna make it get any better,and in any case probably make it worse if you start modding it.

Also my advice, go for the 4x4. You spend a little more, gas mileage is the same on them now-a-days, and they hold their retail value a whole lot more than a 2 wheel drive model, as I found out when I sold mine. More demand for 4x4's.

Mine gets a solid 25.6 mpg per Imp gal (21.3mpg/us gal) at 108kph (68mph) on the highway. And 19.4mpg/imp gal (16.2mpg/us gal) city driving. At 108kph on the highway the tach runs at 2100rpm. If I drive faster than 110kph mpg drops significantly.

I've got a 05 Z-71, 5.3L/auto/4.10 gears/17 inch tires/all stock, no mods, and power is more than adequate. It actually took a Ford Mustang GT off the line at a red light the other day.

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Alright thanks, but unfortunately. I don't need 4x4 and I don't plan on racing. But knowing myself, I can't keep anything stock.

Mark_in_Tulsa · May 8, 2006

Well adding things to your vehicle to get better MPG is like wrapping a twinkie around a power bar. By the time you get through the twinkie it will counter act the power bar.

Say you spend 300 bucks on a part that increases your mpg by 1. At 3 bucks a gallon, you would have to buy 100 gallons to make up for the part. My point is, buying toys for your truck to save money on gas isn't a wise investment.

But then again buying toys for your truck to make it faster is.