I recently bought a used 2002 GMC Sonoma Crew Cab 4x4. The truck is loaded and the mileage and price were right. The only problem is that the Gas mileage sucks. Really sucks. I thing the truck is getting like 12mpg. Runs great but eats gas. Anybody got any suggestions. I am switching to AMSOIL and an AMSOIL air filter soon. I hope that will help.

Tune-up? When was the last time you did a complete tune-up? Plugs, wires, cap, rotor, air filter, pcv valve. A bottle of injector cleaner wouldn't hurt either. Does it run okay? Do you smell gas? Where does your temperature gauge stay? (stuck thermostats are a common problem with these things and if the temp. doesn't get high enough the computer won't go in closed loop and this will hurt your fuel economy...mine used to stay a little below a 1/4 and I didn't know it was a problem til I came here, I changed the thermostat and got another 1.5 mpg)

Unrelated:
If you haven't done so you are also due for an antifreeze change too. You need to change your radiator cap with one not made by AC Delco too.

Also, where does the temp gauge get to when the engine is completely warmed up?

If you switch to AMSOIL make sure you still change your oil every 3-5k miles, oil is oil and after this amount of time the additives in the oil will break down and will destroy a motor. Also remember manufacturers are also concerned about economy so they wouldn't make an air filter the restriction in an intake system, it will only help if you replace a dirty filter with a new one.

If you switch to AMSOIL make sure you still change your oil every 3-5k miles, oil is oil and after this amount of time the additives in the oil will break down and will destroy a motor. Also remember manufacturers are also concerned about economy so they wouldn't make an air filter the restriction in an intake system, it will only help if you replace a dirty filter with a new one.

Please stop posting garbage.

Amsoil GUARANTEES their oil for 25,000 miles.

Learn something about motor oil and then post.

Show me one study that proves AMSOIL is a better oil than any other. I can show you numerous studies that prove all oils break down at the same time. AMSOIL is no different than Penzoil except for the price.

Just to test your knowledge, what is the main difference between Amsoil and your penzoil conventional oil.