Does anyone have a clue what type of mileage I should be getting on my 99 Chevy Express 3500, one ton, 2 wheel drive, 5.7 Liter vortec, with the heavy duty transmission. I have gotten as low as 10.5 and as high as 15.5 today after I cleaned my EGR valve thoroughly. I know its not going to be a high number, you won't depress me. I have had the van for 5 years now, its a work van with ladder racks on the top and probably has 500 lbs worth of tools typically riding along with me. Bought the van used and never really knew what kind of mileage to hope for. I was pleased with the 15.5 I got today, hoping it is not a fluke or a calculator mistake.
Thanks!

 

I think 15 is a good number based on the weight and shape of the car.

 

I have the same set-up as you, ladder rack and tool bins inside and I get 11-13+ depending on how I drive of coarse and if the air is on. Were stuck with bad mileage!

 

I am running a similar rig and weight on a 2003 Chevy Express 3500 w/ 6.0 L engine and if I can believe what I was told, a 3.73:1 rear end.

I bought the van used in March 2011.

It was getting 13.18 MPG until about 3 months ago. The mileage has dropped to 11.64, 10.77, 10.6 over my last fill-ups.

Do you have any tips on cleaning the EGR?

01-31-12
tbb2
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Addendum June 2016
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I just replaced the fuel filter and the clean white catch container I used has a frightening amount of black particulate in it.

It is a good possibility that the corrosion of the fuel filler pipe put dirt into the gas tank. (see other post)
I am now concerned the fuel tank needs to be dropped and flushed.

I am going to be back checking my gas mileage to see if the new fuel filter makes a difference.

 

I simply used brake parts cleaner and a Q-Tip. Squirted it real good and rubbed it with Q-Tip where ever I could. Tried to get all the black "fuzzy" deposits off. Pushed on the valve part until it was unstuck and sprayed it real good. Let it dry and reinstalled. Made vehicle run better and smoother, not sure if mileage got that much better. However the biggest thing I did was build a little roof over my ECM module because when it rained, snowed or even had a heavy dew, moisture would drip down off the windshield and onto the computer box. Great design. The water shield is not large enough. I placed a ruber floor mat over the ECM as a temporay solution (which actually has turned into a permanent solution). The van would act as if it had water in the gas tank, acted as if it had bad plugs, sometimes I could only get the van up to 25 - 35 mph. What was happening, somehow water was dripping down off the water shield directly onto the ECM connections and causing big problems. After building my "temporary" solution I have not had a problem for 6 months. Good Luck,ejr