Which Chevy Or Gmc Full Size Gets The Best Gas Mileage? 1988-1998?

nx02nx02 · March 16, 2007

Hi there. I need some advice. I am going to buy a truck here in the next couple of weeks and as long as everything else is good on the truck I am mainly concerned with gas mileage. I will probably buy a 1988-2000 Chevrolet or GMC 1500 or 2500. Is there a list or something somewhere where I can look up all these old trucks and see what gas mileage they get? I need a truck but I will never buy one again without doing research on the gas mileage.

What I really need to know is what are the top 5 gm trucks for gas mileage, 1988 - 2000. (Other then Duramax ofcourse). I cant get one of those yet.

As long as it's a 1500 or 2500 im interested in it.

Should I consider the 4.3 W/T?

Should I consider a older chevrolet Diesel?

Or what is the best old GM fullsize truck for gas mileage?

Any older fullsize gms get 25 MPG?

I would be doing a little bit of towing with the truck but not too much weight.

Sorry if this is the wrong forum. I didn't know for sure which to put it in. I debated putting it in the classic forum but my posts aren't getting much attention over there.

silveradoHO · March 16, 2007

If you go 88-98, try and get a 5.7, 99-00 geta 5.3. The 4.3V6 is a great motor but in a vehicle this big it is a little underpowered, and from what post I've read about them they really don't get any better mileage than a V8, especially if you do much towing. I had a 97 2wd ecsb with the 5.7 and I got 15 city( I was also 16 at the time with a heavy foot) and 20 highway. The 05 I have now is about the same.

thecraft · March 16, 2007

Go with the 1500, that's less gas the engine has to use pulling extra weight.

If you do mostly flat highway driving, the V6 should get you 20+ MPG. But if you take it into the city, up hills, or put a trailer behind it, the mileage is going to be a killer. In that case, you'd be better off with 5.7L, it's a bulletproof engine. Since I ran a can of Seafoam through my gas tank a few weeks ago, my mileage went up to about silveradoHO's '97, 15 city/19 highway. It was 14 city/17 highway before that.

Also, pay attention to the rear axle gearing. High gears (lower numbers like 3.08 and 3.23) will give you great highway mileage while lower gears (3.73, 4.10) will give you better takeoff and towing performance (and typically better city mileage). You can tell what gears the truck has (unless they were changed) by looking at the RPO code sticker inside the glove box.

GU2 = 2.73 Ratio

GU4 = 3.08 Ratio

GU5 = 3.23 Ratio

GU6 = 3.42 Ratio

GT4 = 3.73 Ratio

GT5 = 4.10 Ratio

And no go on the diesel, the extra mileage would be offset by the higher price of diesel.

srlbotanical · March 16, 2007

Its a truck. Unfortunately mileage is going to suck.

I average 15mpg if I keep my foot out of it.

The info on gears that Kyle listed above is good to know when looking for a truck. If you want 410 gears in a 1/2 ton OBS truck(88-98), they only came as a stock option in the 88-95 1500's. 342 and 373 are the most common, with the 373's being a little better if you do any kind of towing.

Good luck.

67ChevyRedneck · March 16, 2007

Any older fullsize gms get 25 MPG?

There isn't a single fullsize truck from any manufacturer that will do much better than 21-22 mpg highway from a 2wd, and even with that, the best city is usally 17.

25 mpg is also "pushing it" for highway mileage from a midsize truck (excluding 2wd 4 bangers.) Our 2005 Tacoma pre-runner V-6 only gets 21 mpg highway.

The best mpg you're probably going to get is with a reg cab 4.3L 5 speed silverado. Maybe 17 city and 20-21 or so highway, if you keep it under 70.

The average V-8 fullsize trucks get between 13-15 city and 15-19 highway. Depends on how they're driven. The 99+ trucks seem to get better mileage than the older ones.

If fuel mileage is your biggest concern, you may want to rethink what you really want to buy and what you need.

Hope this helps some.

bartlanz · March 16, 2007

Any older fullsize gms get 25 MPG?

There isn't a single fullsize truck from any manufacturer that will do much better than 21-22 mpg highway from a 2wd, and even with that, the best city is usally 17.

25 mpg is also "pushing it" for highway mileage from a midsize truck (excluding 2wd 4 bangers.) Our 2005 Tacoma pre-runner V-6 only gets 21 mpg highway.

The best mpg you're probably going to get is with a reg cab 4.3L 5 speed silverado. Maybe 17 city and 20-21 or so highway, if you keep it under 70.

The average V-8 fullsize trucks get between 13-15 city and 15-19 highway. Depends on how they're driven. The 99+ trucks seem to get better mileage than the older ones.

If fuel mileage is your biggest concern, you may want to rethink what you really want to buy and what you need.

Hope this helps some.

+1 Look at the NBS trucks, mutch better gas mileage

silverado3500 · March 16, 2007

A 96 or newer 4.3 will give good mileage. The 4.3 is not underpowered at all for a regular cab 1500. Ours gets about 19 city and 21 hwy (at 85mph). Ours is a 96 with the 4L60E, 3.73 axle ratio, and has plenty of pep. It won't be a rocket towing, but ours has no trouble towing the boat , or a u-haul trailer in the mountains of North Carolina.

A 99 and newer 5.3 will give silimar mileage to the 4.3, but only if you don't push it. The 5.7 is a good engine, but is definately more thirsty.

a 96-98 long bed will probably have the 3.73 ratio, and this is what I'd suggest searching for. The 3.42 or higher will feel like a dog, and the 4.10 will have you wasting fuel on the highway.

silveradoHO · March 17, 2007

Is there any reason in particular you need a full size? If not, consider a S10 w/4.3, it will get better mileage than just about any fullsize. If you need a full size, best bet is a nbs w/5.3 for gas mileage. I have an 05 ecsb with the 5.3 and 3.42, definitely not a dog. With a couple mods I run 0-60 in 7.1 seconds and get 20mpg highway running 80mph.

nx02nx02 · March 17, 2007

Thanks for the replies everyone. Very helpful, what is nbs? And I thought the 5.3 didn't get very good mileage?

I have a couple friends with 99-2000 5.3's and they get at best 13 mpg. Or maybe your referring to a different truck? theirs is x-cab 4x4's 1500's.

rogerf · March 17, 2007

Thanks for the replies everyone. Very helpful, what is nbs? And I thought the 5.3 didn't get very good mileage?
I have a couple friends with 99-2000 5.3's and they get at best 13 mpg. Or maybe your referring to a different truck? theirs is x-cab 4x4's 1500's.

I think you nailed some of the reasons, heavier x-cab, 4X4, 5.3L, etc...and possibly 4.10 diff's or heavy foot? I just sold a '97 C1500 W/T reg. cab, long box, 4.3 V-6 automatic, 3.73 diff. Got a consistant 20 mpg, 600+ miles from a tank of fuel. The V-6 ran fine for what I needed to do and wouldn't hesitate to buy another. Now the replacement is going to be a NBS (new body style) '07 with a 5.3L 4X4 and would be tickled if it delivers anything close to 20 mpg.

srlbotanical · March 17, 2007

Thanks for the replies everyone. Very helpful, what is nbs? ...

OBS = old body style 88-98

NBS = new body style 99-06

UBS = ugly body style 07- (just kidding on this one... Maybe the new trucks will grow on me )

silveradoHO · March 17, 2007

Thanks for the replies everyone. Very helpful, what is nbs? And I thought the 5.3 didn't get very good mileage?
I have a couple friends with 99-2000 5.3's and they get at best 13 mpg. Or maybe your referring to a different truck? theirs is x-cab 4x4's 1500's.

I think you nailed some of the reasons, heavier x-cab, 4X4, 5.3L, etc...and possibly 4.10 diff's or heavy foot? I just sold a '97 C1500 W/T reg. cab, long box, 4.3 V-6 automatic, 3.73 diff. Got a consistant 20 mpg, 600+ miles from a tank of fuel. The V-6 ran fine for what I needed to do and wouldn't hesitate to buy another. Now the replacement is going to be a NBS (new body style) '07 with a 5.3L 4X4 and would be tickled if it delivers anything close to 20 mpg.

My 05 is an extended cab Z71. MPG rating when I bought it was 15 city, 19 highway, and I've always got a little better than that. I'm sure it wouldn't do that with 4.10s though

95Sierra2500 · March 17, 2007

My fiancee`'s dad used to have a '93 regular cab, long box, 4x4 GMC with a 4.3, 4L60, and 3.73's, and he'd pull off an easy 20 mpg highway, 17 city. He could drive that thing just about anywhere and had no issues towing or just driving. It hauled their enclosed car trailer and their drag car across the state just fine. If you're simply after fuel economy, a 2wd truck similar to this would be your best bet. Just remember it isn't built to be a street stomper.

rogerf · March 17, 2007

Thanks for the replies everyone. Very helpful, what is nbs? And I thought the 5.3 didn't get very good mileage?
I have a couple friends with 99-2000 5.3's and they get at best 13 mpg. Or maybe your referring to a different truck? theirs is x-cab 4x4's 1500's.

I think you nailed some of the reasons, heavier x-cab, 4X4, 5.3L, etc...and possibly 4.10 diff's or heavy foot? I just sold a '97 C1500 W/T reg. cab, long box, 4.3 V-6 automatic, 3.73 diff. Got a consistant 20 mpg, 600+ miles from a tank of fuel. The V-6 ran fine for what I needed to do and wouldn't hesitate to buy another. Now the replacement is going to be a NBS (new body style) '07 with a 5.3L 4X4 and would be tickled if it delivers anything close to 20 mpg.

My 05 is an extended cab Z71. MPG rating when I bought it was 15 city, 19 highway, and I've always got a little better than that. I'm sure it wouldn't do that with 4.10s though

I sold that '97 W/T yesterday to a mechanic at work that is replacing his V-8 powered '89 Chevy 1500 (with 200K+). He could not believe how strong the 4.3L V-6 ran. Still amazed, I posted that truck on the company intranet and it was gone in a few hours for @ $2K less than I paid for it 5 years ago.

My brother-in-law says he gets 19 mpg from his '04 Sierra x-cab 4X4 Z71 on long trips. I might be surprised and get that magic 20 mpg from the new one as I do mostly expressway driving.

thecraft · March 17, 2007

The 3.42 or higher will feel like a dog

Whoa now, an OBS truck with 3.42s is definitely not a dog. You've got consider the size of the tires you're going to be running, smaller tires will virtually increase the gear ratio while larger tires decrease it. My truck has 235/75P15 (28.9") tires, while the NBS 2wd trucks came with (I think) either 245/75R16 or 245/70R17 (both 30.5") tires. So 3.42s in the OBS trucks are like 3.61s in the NBS trucks. http://4lo.com/calc/geartire.htm