bad fuel mileage

Hi I have a 1998 GMC sonoma 4.3 truck runs good but i only get around 150 miles on a tank of gas. Tune up was done a few months ago, no codes and no check engine light. any help will be appreciated Thanks

 

Too many variables to be able to help you pin it down. Can you supply more information such as size of the gas tank, driving style, terrain ( city / suburban / county or open road. Average gallons per refill, etc.

Have you owned the truck for a while and seen the mileage fall or is the truck new to you. Have you done checks to see what your MPG really is.

Fill the tank and record the mileage. At the next refill, record the mileage again along with the number of gallons it took to refill. Subtract the original mileage from the latest mileage and divide the result by the number of gallons you put in. that will give you MPG. Let us know what you find.

 

First thing they say around here is . Change the fuel filter. Why I dont know

 

I own this truck a few years I only drive 4 blocks (city) to work and back and sometimes 20 miles to another work location which is highway. i never checked mileage close before but i always got better mileage. i can watch the gauge drop now in a few miles. Tank is 18.5 gal and it takes that much to fill when empty. I am the only driver and i dont drive it hard. bought truck with 20 k now has 50 k miles. I checked for codes with a code reader and no codes. If I have a bad o2 sensor (from short runs) would there be a code?
Thanks

 

Yes there will be codes if anything is detected by the E.C.U.
Check your air filter. Also what altitude are you at.
I drive a 90 astro cargo van and it has the 4.3 non vortec and it gets 17 mpg

 

Is it shifting correctly if an automatic? If 4x4, is the the 4 wheel disengaged?

 

Couple of questions:

1. Did the mileage change abruptly or go down hill over an extended period of time?
2. Any change in driving habits or have you been doing the same driving routine for a while?

Just a side note, but starting the truck up and driving four blocks to work is going to be really hard on the engine over time and I'm thinking there may be a relationship there.