Q: Low gas mileage on 1997 GMC K1500 Suburban V8-5.7L

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My car has gone close to 250,000 miles. It's been getting very bad gas mileage. It used to get 15-17 MPG and now it has dropped to 7-9 MPG. I had the engine rebuilt so I was wondering if that might be causing such low MPG. The transmission is slipping ocassionlly also. There is a leak in the exhaust. I'm aware that it's a high-mileage vehicle but is there a way to improve the gas mileage?

Hello. We will be happy to help with your 1997 GMC K1500 Suburban. There’s likely a combination of reasons as to why your MPG has so greatly declined. I suggest that you have a technician inspect the following items and perform the needed repairs.

Flush out the fuel injectors using an injector flush kit, replace your fuel filter, inspect the spark plugs and wires (and replace if necessary), check the air filter (replace if found dirty). Cleaning a dirty mass airflow sensor will help increase the MPG as well. I also suggest that you check the pressure and condition of the tires. Low air pressure or bad tires will decrease in MPG, too. If you would like to have this inspected by a professional, a qualified technician from YourMechanic can come to your car’s location to diagnose your mileage issue and let you know what should be done.

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