'91 GMC bad gas mileage

[FutureEscort13]

my dad has a full size van/bus with the 5.7 efi engine from the early 90's. Its getting very poor mpg and we were wondering if it could have anything to do with the temperature sensor, the one that regulate the amount of fuel mixed based on temp or something like that...thanx

[n4byojim]

Originally Posted by FutureEscort13

my dad has a full size van/bus with the 5.7 efi engine from the early 90's. Its getting very poor mpg and we were wondering if it could have anything to do with the temperature sensor, the one that regulate the amount of fuel mixed based on temp or something like that...thanx

Help us understand what "bad" means.
I have a '91 GMC Van with the same engine. On a good day, I get 15.5 to 16 MPG on the Highway - and 10 - 12 in town. That is normal/typical for a heavy, large vehicle. What are you getting?

You may get better mileage if you do the following:
1. Replace the air filter every 30,000 miles
2. Replace the spark plugs every 60,000 miles
3. Keep the MAXIMUM air pressure that your tires will allow.
4. pour (cheap) carb/fuel injector cleaner in the gas tank twice a year.
5. use semi synthic oil or full synthic oil in your oil changes
6. Pretend that an egg exists between your foot and the gas pedel - moving that much weight from a dead stop is killer on gas mileage.

[n4byojim]

Originally Posted by n4byojim

Help us understand what "bad" means.
I have a '91 GMC Van with the same engine. On a good day, I get 15.5 to 16 MPG on the Highway - and 10 - 12 in town. That is normal/typical for a heavy, large vehicle. What are you getting?

You may get better mileage if you do the following:
1. Replace the air filter every 30,000 miles
2. Replace the spark plugs every 60,000 miles
3. Keep the MAXIMUM air pressure that your tires will allow.
4. pour (cheap) carb/fuel injector cleaner in the gas tank twice a year.
5. use semi synthic oil or full synthic oil in your oil changes
6. Pretend that an egg exists between your foot and the gas pedel - moving that much weight from a dead stop is killer on gas mileage.

Good luck

[SHAWNEXLEY]

change youre plugs and youre wires and posable go with an aftermarket coil if you have any oil blow bye in youre system it might be puging up the spark plug gap causing bad gas milage so the after market coil will put out a little more juice and help keep the plugs clean plus give you a bit more power