Yep, I get as low as 17 sometimes since I replaced my MAF sensor (I put in a AC Delco unit from Amazon which was not the original part number and had an adapter for the wiring harness) which fixed the limp mode which was corrected with the scanner clearing codes. Before I cleared the codes, I would get up to 21 mpg or more on a long highway trip. However, I had power problems. Once I replaced the MAF, this thing rips and can go to the speed limiter (96 mph) no problem.

Anyway, I have the same problem about the large tank and only being able to put a smaller amount in the tank. I have the 2000 Blazer with four doors, so my tank should be 18 gal according to Mitchell On Demand. The most that I've ever put in was 16 gal.

Now my fuel gauge on the dash is messing up. Sometimes when parked it goes from empty to fully full, and sometimes it messes around near where it should be. All three conditions during a warm-up period. If anyone that reads this has suggestions about where I should start with that problem, good on ya, let me know where to look!

 

From what I heard,.If your fuel pump is original and your having problems?It best to have someone drop the tank, replace fuel pump and everythingb else that goes with it.

 

Sending units are notoriously unreliable on these things. Before swapping that out, check all the wiring first.

If you're gonna drop the tank to replace the sender, might as well replace the entire assembly, because the fuel pump is just as "reliable".

 

1997 Chevy Blazer LS 4x4 4.3L Vortec. Driven in 2wd. Driving habits are slow acceleration compared to most aggressive drivers on the road, I'm the guy that most people either ride my bumper or overtake. Mostly city miles, with an exception of about 40 miles highway at 70 mph (fast for me; Typically I keep it between 55-60 mph). Weather in Ohio at this time is about 50 degrees on average. I'm experiencing about 18 mpg.

 

After I had the (leaking) original fuel pump replaced (with an OEM Delco) the mileage dropped about 1mpg.

 

I have the same truck (a '98) and same driving habits with about the same results. I've monitored mileage over the years and consider my Blazer to be basically a 20mpg vehicle, averaging about 21/22mpg on the hwy, 17/18 in town. (In response to an earlier post, my low fuel light also comes on with 5 or 6 gallons left in the tank.)

 

I can get 19-20 on pure freeway driving, but I live in the Sierras, so it runs 16-17. Not too bad, really, as this includes some snow driving.
'99 Blazer LT 4WD

 

I've been getting 13-14ish. But that was before I did a tuneup. I'll have to see how it goes now that that that task is done.

 

97 4x4. 4.3L t-bar crank, 2" shackles, 2" body lift, 31" federal m/t's. average just at 13 mpg combined city/stop and go traffic. will post update after SAS to GM 10 bolt axles with 4.88 gears, chromoly shafts, and 37's.

 

I just bought a 1999 Blazer LT 4WD. I haven't done a tune up yet, but I did change the air filter and put on some new tires (235/75R15, apparently Michelin doesn't make the spec 70s any longer). According to my aCar app, I'm getting about 13.8 MPG on the first two fill ups. I plan on going through a few tanks, and then doing a tune up.

I like the press the gas.