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Lack of Fuel Economy

My 2003 Chevy Blazer gets approximately 12-13 mpg around town. I previously owned a 1999 Blazer that averaged 16-17 mpg around town. They both had the same 4.3L engine in it and I don’t drive my 2003 any different then my 1999. What could cause this?

What are the EPA ratings for both?

Are your tires properly inflated? Is your check-engine light on? Have you checked if any wheels are hotter than the others after a long drive (indicating that the brake caliper is sticking)? Did your gas stations switch to E10 gas about the time you changed cars? Are you comparing summer mileage to summer mileage?

How many miles on it? Has it always had lower MPG? Check engine light?
Could be:
tire pressure, wheel alignment, dragging brakes, stuck thermostat, thick oil…
lots of other things if the CEL comes on.

The summer mpg on my 2000 Blazer went from 19 to 17.5 when NJ mandated E10 year round. More aggressive off-road tires will lower mpg also. Winter mpg is arount 16-16.5 mpg

Any brake work done recently? Sticking calipers after the rear brakes were changed (at 80k) on my Blazer dropped the mpg to around 12-13 mpg.

I measure mpg every 3 or 4 tanks to average out under or overfilling the tank.

Ed B.

The EPA city mileage is 15 MPG for the 2WD and 13 MPG for the 4WD.

Thanks for the input guys. I checked alomost everything mentioned here except the EPA ratings for both. I’ve used E10 in both and had no trouble. Looks likes this gets worse mpg than my '99.