You have my '04x4door 3:42 beat. I average 14.5-15.5 with a high around 18 @ 55-60 on highway, any faster and mileage drops 201,000 miles.

2002 4 door 4x automatic 240,000 miles
About half city half highway… or maybe 1/3 highway 2/3 city counting stop n go traffic as city.

Starting in February with snow and sub-zero temps I got 12.5 mpg, then as the weather improved it’s gone as high as 14.2.

I’m still not sure if that’s good or not. Seems a bit low, but not horrible.

I used to get 18 out of my '00 Jimmy, then 17.5 later when the engine was carbureted and put in a '89 S10 Blazer. Definitely a bit low, but depends on how you drive it and its state of tune.

If the o2 sensors are old and/or cheap aftermarket brands it wouldn't hurt to change them. New cap, rotor, plugs, and wires wouldn't hurt either if it's been a while. Make sure the air filter and MAF are clean, too, and fix any and all vacuum leaks. There's plenty of low-bidder vacuum hose on these that deteriorate and fail.

Huh. Just pulled an OBD P0507 code. No check engine light and I don’t know how long it stays in memory, but I guess I’ll start looking there (as well as the other things just mentioned)
I’ve only had this for a couple months, first fill up was Feb 18 so I started driving it about the 10th after it was sitting for months and driven by a teenager for a few years before that

Could just be semi-stale fuel that needs to be run out of it. I'd drive it a while first & get some fresh gas in it before doing anything. Run as much of that old crap out of it (as much as you dare before running out) before getting fuel, though.

If it's still got the code after that, and slamming into gear from park or neutral you could try cleaning the throttle body, BUT, you'll need a bi-directional scan tool to do an idle relearn procedure.

The light SHOULD be on for that code, unless it's pending, or a history code. Kid may have removed or destroyed the bulb or LED in the cluster to keep the light off. I've seen that MANY times in the shop over the years.

Well, that’s one thing I’ve figured out. All the dash lights have been replaced with a resistor and LED, which explains the ziplock full of bulbs and sockets in the bottom of the glove box. But a couple of the replacements on the left side aren’t working, including the check engine.
I was driving a Bonneville with red dash lights before this, so I didn’t think anything about the blue tinge to these lights. Just thought I was used to seeing red.

Anyway, since the kid was thoughtful enough to save all the old parts, I replaced the check engine bulb and I found out it actually says “service engine soon”

Which doesn’t help my mileage at all, but it’s something. This weekend I’ll start at the air filter, work down the list, and see what I can get accomplished.

Thanks

ETA: smoothest shifting vehicle I’ve driven in years, so it’s not slamming into gear. But I have plenty of things to check/clean/repair/replace so eventually I expect it’ll get better

You're welcome. Yeah, "service engine soon" - different wording for the same thing. Good luck on the project - sounds like you got a good one. :icon_beerchug:

I bought my 2002 S/T Blazer from a neighbor who let it sit for over 5 years. I got it REALLY cheap, and quickly put in north of 4 grand and got it pretty well fixed up. Problem is, with conservative overall driving, it gets only 14.5 MPG. I intend to replace the rear O2 sensor, inasmuch as it is the only remaining original fuel correction sensor. We shall see.

Depends on axel ratio, terrain, weather and especially how hard vehlcle is driven.
Have 3.73's
Been careful can attain 18 highway US mpg driving easy. With 3.73's 50 mph is best economy, 60 mph drops to 15 mpg 70 mph gives 11.5 mpg.
in town about 13 US mpg.
Have 195000 miles on the old girl.

When I attended GM training school, the instructor taught the importance of volumetric efficiency overall as opposed to just one factor regarding fuel efficiency.

. Years later, that really proved out to me. I owned a generation 2 Mazda Miata with a rare automatic transmission option. I drove the car on round trip from Houston, Texas to Philly and back in August of 2007. My overall speeds averaged well above 70 mph. My fuel mileage was an impressive 40mpg overall. At 70-75 MPH, the tach was just under 4,000.