5.7l Mpg?

NFSGamerUSA · March 14, 2008

Is it just me, or am I getting absolutely horrible mileage? Right now I'm getting less than 10 mpg. Almost all driving is done around town without any load (save for hauling a 450 pound ATV for three miles total on most weekends) at speeds topping out at around 50 mph occasionally. I'm pretty light-footed, at least going by the traffic around here. I take my time accelerating while others are shooting on ahead with the regular flow of traffic. My truck is a bone stock K1500 extended cab with a short bed, and the current mileage is just above 138,000. It has the Vortec 5700 and 3.42 final drive. It seems to be running just fine and there's no indication of problems. What's the deal (anyone have any ideas)? I wouldn't expect this type of mileage unless I were driving around lifted a few inches with substantially large tires.

Now, I may be answering my own question here, but I'd say about two-thirds of the time I crank my truck in the morning to warm up for about five minutes. This seems to be the most likely suspect, but am I actually sacrificing THAT MUCH fuel by letting it warm up for five minutes when it's cold?

mitchell87 · March 14, 2008

1. Driving around town kills milage

2. I don't think the 5.7 was know for its milage

3. Letting it idle will hurt the milage

4. Try speeding up a bit quicker and then letting of the gas sooner, I have heard this works, but i don't have the patience to do it all the time as i have a very heavy foot, size 15 baby

mitchell87 · March 14, 2008

O and by the way i have a 94 350 and i get ten mpg's with the atv behind me on a trailer while going 70

NFSGamerUSA · March 14, 2008

I realize it's not going to get good mileage around town, but again, I'm not getting much better than most people running large tires do. I would expect at least 12-13 mpg around town. According to fueleconomy.gov, people with the same truck as I get around 13 mpg average in the city (by their own estimates, not the EPA's), and I know most aren't as light on the throttle as I am. My tires are stock size, BTW; 265/75-16. I have the ATV in the bed if that makes a difference...in those three miles.

sgfootball2006 · March 14, 2008

I have a 99 Tahoe 5.7L. I have the 3.42's and 32" BFG A/T tires

I get about 11-12 city 15-16 averaging around 75 highway

Only performance mods are drop in, exhaust, and short tube headers. I also have an 80lb grill guard on the front that probably does not help with highway.

NFSGamerUSA · March 14, 2008

I have a 99 Tahoe 5.7L. I have the 3.42's and 32" BFG A/T tires
I get about 11-12 city 15-16 averaging around 75 highway

Only performance mods are drop in, exhaust, and short tube headers. I also have an 80lb grill guard on the front that probably does not help with highway.

Just out of curiosity, did you gain any mileage in adding the headers and exhaust? I've been told the stock exhaust system decreases mileage versus a more open exhaust. I wouldn't want to sacrifice low-end torque, though.

NorCal57 · March 14, 2008

I just posted in the 5.3 thread in regards to my current truck and mentioned my old truck with the 5.7. The old truck was a GMC 2500, ECSB, 4x4, 5.7 with 31" tires and it got about 9 mpg around town and 12 out on the highway....13 on a good day. Actually, it got 16 one time on the way back from South Lake Tahoe but most of that is down hill, barely on the throttle for 50 miles.

I did a job last year that was just about 6 miles from my house but on top of a hill. The truck averaged 6.4mpg! The profit from that job was darn near eaten up by that old truck

silversport · March 14, 2008

I have a 2000 Escalade (think 1999 Tahoe) with the Vortec 350...I do mostly city driving...12MPG in the warmer months...10-11MPG in the Winter...I don't lead foot it either...I think that is the nature of the beast...for contrast...I had a 2002 Avalanche for about 3 years with the 5.3...nearly identical mileage...high 11 in the Winter...driving the same routes, same types of driving...the 5.3 did better on the one big highway trip I took it on...good luck...still enjoy my Esky...

Bill

sgfootball2006 · March 14, 2008

I have a 99 Tahoe 5.7L. I have the 3.42's and 32" BFG A/T tires
I get about 11-12 city 15-16 averaging around 75 highway

Only performance mods are drop in, exhaust, and short tube headers. I also have an 80lb grill guard on the front that probably does not help with highway.

Just out of curiosity, did you gain any mileage in adding the headers and exhaust? I've been told the stock exhaust system decreases mileage versus a more open exhaust. I wouldn't want to sacrifice low-end torque, though.

Yes. I forgot to mention I have a lead foot too. When I first got the truck, it just had true dual glass packs that sound a lot different than other glass packs I have heard. These actually sound like a regular muffler imo. I was getting 10mpg city and about 12 highway. I installed new spark plugs, spark plug wires, drop in k&n, short tube headers, and a custom made xpipe to even out the pressure of the true duals. Now I am getting the mileage as stated above.