Me and the little woman are looking at a 1990 2wd Suburban and have seen (on Autotrader) that they are rated at ~18mpg on the freeway. Just wondering what others are getting. We will be using for mostly taking trips this spring and summer.
The one we are looking at has 61,000 original miles but the paint is coming off the roof real bad and it has few dings. Other than that it is pretty nice.
Also, I've seen advertised HP ratings from 175 to 210 for the 5.7 this year? Anybody have any ideas what it actually might be.

I think mine gets inteh neighborhood of 15 or so, but it could probably use a bit of a tune up. The HC was high when it went for the inspection.

The mpg numbers vary a whole bunch depending on the transmission, engine, axle ratio, and tire size.

Anywhere from 10-20 mpg what I would expect without knowing the exact specs and driving conditions.

HP rating is 190 or 210hp depending is above/below 8500# GVWR. Pic (http://brochures.slosh.com/1990/gmc8.jpg)

Thanks for posting that, it was informative!
Any idea how you tell what the GVWR is?

I have a 90 and it gets about 18 on the highway and it has 198000 miles. It has the 5.7 efi and 700r4 tranny.

My dad said he gets ~15 around town in his '94 Sub 2wd w/350, TBI, & automatic trans. I drove it ~250 miles on 2-lane highways on a parts run and it got about 17.

I wonder how much, if any, the change to the body made for mileage?
My dad said he gets ~15 around town in his '94 Sub 2wd w/350, TBI, & automatic trans. I drove it ~250 miles on 2-lane highways on a parts run and it got about 17.

Thanks for posting that, it was informative!
Any idea how you tell what the GVWR is?

Sticker is on the edge of the drivers door.... or you can decode the VIN to get the GVWR range.

1/2-tons are under 8500# for sure. 3/4-tons can be either... 7200(?) or 8600#.

The difference is a TH700 (OD & lockup trans) with say a 3.42 ratio is gonna do a heckuva lot better in the MPG department than a TH400 (non-OD, non-lockup) and 4.10 ratio.

My 86 with a freshly rebuilt 350 and old 700R4 got about 14.5MPG on the highway. My 97 with 116k and Vortec 5.7L gets about 16.5 -17 on the road. I think the 97 is more aerodynamic so it has probably less drag than the older body style. Lots more things to break though, and I'm finding out there's not a helluva lot I can fix on this one. :( :(

with a 350 TBI you can expect around 12-15mpg
with a 454 TBI you can expect 8-12 mpg

around town in my 91 R2500 with 454TBI I get about 8mpg but on the highways I have seen up to 12mpg... and this is with it at 170K miles....

go to www.carpoint.com to see GVWR's, engine specs, etc...

sticker for my '89 1/2ton 2wd w/ a 700r4 and 3.73 axle was 14/19 (still have the sticker). I get about 16mpg highway... once I got 18 with cruise on and literally gas station to gas station, both on the highway... and going 70mph.

with this body style, I get the feeling the wind resistance makes a big difference... it's much easier for me to go 55 than 70 (and I think I'd get much better milage at 55mph)...