Average Fuel Economy

Just wondering what the Driver Info Center is telling you that your avg fuel economy is....Mine used to say around 20 on the interstate on about 16-18 in the city. Well, after I pulled a trailer for over 1000 miles (Only about a 2000 lb trailer) I got a SES light.

When I took it in, they said it was running rich or lean, and it was fine and they just reset it. Well now it says I only get about 15 in the city, and 16-17 on the hwy. Sounds like something is wrong to me. I would be interested to see what you guys are getting.

I was wondering about that too.... When I first got my truck, it was nailing near 19mpg average. For the last few months, however, its only been getting 15mpg. I think a big part of it is the switch to the oxygenated fuel in the winter....but still. Most of my driving is highway....around 70-80 though.

I'll be able to give you some DIC figures after this weekend, as I have to run the wires from the column to the cluster to switch between functions... Everything else is hooked up and working perfect :)

I'm getting 19.7mpg on the DIC right now with the cold weather. Last fall I was at 20.3mpg. These figures are from a 02 LTZ.
Sounds like you might be running in some sort of "limp" mode due to the SES.

Why not try & go out on the expressway & stomp on the gas from 50-70+ a few times to clear out the cobwebs from it running rich?

I have been told to do that from time to time.

Don't know if it really works or not, but when you do it a couple of times, you will see a bunch of black smoke come out at first & then nothing.

Try it & see....


My V8 gets around 14-15 around town when I am driving nice. About 11.5-12 something when I am not being nice.

Highway, I get about 18+...but I normally don't keep a solid speed & so the lower MPG. I am going to Indianapolis this weekend & I will "try" to keep my foot out of it...LOL! ---see what she can get.

The inline 6 on the highway, I used to get 20-21MPG & something like 15-17 around town.

Quick addition to this....

Now that I finally wired up my new steering wheel to run the new cluster with DIC, I was able to test the MPG today. Note, the instant MPG doesn't work yet, as I assume it needs some parameters from the "Program Cluster" routine to work. That being said, my avg MPG at 60 was around 20-21. I reset the cruise for 70 and reset the avg MPG...mileage dropped to 18! 80mph was pretty close, at 17mpg. So.....I think the poor mileage is more or less due to my driving at 70-80mph on the expressway. I'm pretty shocked that there is this big of a difference, but I guess there is. I'm going to *try* and drive this tank at 60mph on the expressway, and see how she does overall. Anything around town, however, was crap....

Thanks for the response everyone....do you think a dirty fuel filter could cause some of these problems?? It is an '03, but the dealer keeps saying that Texas gas sucks, and maybe the filter is clogged.

Yes, it could have something to do with it. Depends on how many miles you have. I have been told to have it done every 15,000 miles.

Another thing....did you get a bad batch of gas in her? My dealership has told me to only run Amoco, Shell or Mobil in it. Anything else in time will cause problems....so they say.Have you tried running any kind of a fuel additives?

I have tried this stuff by RedLine (tall red bottle) which is a complete fuel system cleaner. It does everything! $5 per bottle at Pep Boys...if you have one around you & it cleans the fuel injectors & the fuel system & other things. You can dump the whole bottle in for a whole tank for quick work & let it do it's magic. The there are labels on the side of the bottle to add it at every tank if you so desired from there. It is in 10 gal. increments. Other family members introduced me to it & it really make a difference IMO.

Plus also a dirty air filter will make the mileage go south. Can't think of anything else besides lower air pressure in your tires????


Hope this helps.

Thanks...I have about 23k on her right now, I guess I will take a look at the fuel filter and change it. It wouldn't hurt to change it anyway. You wouldn't happen to know the part number would ya?? Should I get one from an auto parts store, or get one from the dealer??

If you have a 2002 with the inline 6, the part number is:

AC Delco part #GF831


Same part number for a 2003, 2004 with the inline 6. Reg. size or EXT.
Same part number it looks like in the EXT with the V8 too.




Source of information: www.rockauto.com


Hope the info. helped :smile:

Ooooops, almost forgot.....best bet is to call up the local dealership parts guy & ask him what they charge & then call up a few parts places & see who has the best price. :2cents:

marc, what year is yours? i have an '05 LS. my fuel economy is about a gallon and a half under what i originally expected.. right now i'm averaging 16.5-17. kinda stinks considering i'm doing roughly 120 miles a day..

I have an 03 LT EXT. I was getting like 13-14. I just changed the air and fuel filter, and now in the city I am getting about 15.5. (I changed it 2 days ago and haven't driven very much, so it may continue to rise)