I used to get about 20-21mpg half city and half highway on the factory engine, but now with the new engine I only get 18-19mpg with the same driving habits. Now there is really only about 1 mpg difference between the two engines, but when the second engine was new and not broken in yet I was getting 14-15mpg on it. I have a 1998 2wd 4dr Blazer with 85,000 mi on chassis and 30,000 mi on engine.

 

seems like some 4.3's do quite well, and others not so much. id have never dreamed that my wifes S-blazer would do better on fuel than my 4.0 ranger (that weighs 1,000 pounds less) our old astro on the other hand wasnt too great on fuel, but its areodynamically different from a blazer and was the old t.b.i. fuel injection setup, only 175 hp too.

 

82 k5 Sierra Classic. 305 with 32" tires. I think the rear gears are stock. I was getting 9 mpg but I fixed a bunch of vacuum leaks and changed the spark plugs and now I'm getting 13 mpg. I also have a thumper cam that I'm hoping to switch out for high torque. Rochester carb.

 

I've got a '83 K5 with a GM crate 5.7L and a 3-speed manual. I just drove it from Vegas to San Diego. All highway driving for the entire tank and I rated just a hair over 10MPG.

 

96 S10 Blazer, 4.3 with high-flow cat, flowmaster, 400lb weight drop (now measure in at 3600lbs with driver) in the mountains of WNC. 23 MPG

 

Stock 2001 4.3 Vortec 4 door 4x4 and I was getting 14 MPG before the old engine blew...averaging 20-21 MPG now with the "new" junkyard motor. I use cruise control all the time where I can. And getting my tranny flushed and other services done has helped. It has 134,000 on it without knowing how many miles are on the junkyard motor.

 

I got 23mpg on my way up to sauble beach, I have a 2000 ZR2 with a 5 speed tranny 180 kms. Oh and I had to smash my cat out because it was plugged. Sounds like a tractor but it feels like I gained 50 hp, my truck was bogging soo badly before fixing that.

 

possibly including engine size, gear ratio, auto or manual transmission, 2wd or 4wd, etc
I live in south florida (heat, sun, rain) and do a mix of driving, but i try not to be too hard on the gas...

1999 chevy blazer LT, about 90,000 to 91,000 miles, Stainless steel pushbar and hi flow catalytic converter would be the only upgrades. btw, this is running on premium fuel. any recommendations on ways to improve fuel economy? i'm getting 14-15 and would like to get better if possible... oh, and the truck runs well (sometimes a little rough idle, but nothing bad) 4.3L v6 and i lose tons of power and economy since my mechanic put in an s-10 air conditioning system (compressor and all) but only when i turn the air on.

 

94 s10 blazer 5 speed standard 4.3 tbi 3.43.Can get about 400 miles of 20 gallon tank 100% city but i live out in the country so i don't really stop.All stock no mods.

 

My wife drives the S10 Blazer only in the winter. She has a pristine, garaged, '86 Grand Marquis for the summer. But between the '91 S10 we had before, the '00 Jimmy, she managed to get anywhere from 18-21 mpg.

I recall the '91 when we first bought it got 13. I changed the o2 sensor & it jumped to 20.

I think all of the ones we had were 3.42 in the rear. All 4.3's. The '91 was a 4-door, & the '89 is a 2-door. The '89 had a worn out engine that burned a quart of 20W-50 in the dead of winter every 50 miles. I think 15 mpg was the best we got out of that.

I'll have to post back once I get the '00 Jimmy engine up & running in the '89. It'll have an Edelbrock 1404 (500cfm, manual choke). I'll have to look at the RPO codes later, but pretty sure it's got 3.42's.