My GMC has been extremely low on gas mileage. I drove to pick up my brother about 5 to 7 miles away, and I had 2 quarters of a tank of gas – a half a tank when I left the house. When I got to my brother’s house I had only a quarter of a tank left. It’s been eating gas like crazy after I got my oil change. I put 5 quarts of oil in, and I still needed to put in two more quarts. I haven’t done that yet. I made the mistake of getting an air filter instead of an oil filter. I had the fuel injectors cleaned last July. Do you have any suggestions that will help me fix this problem?
Decreases in fuel economy are caused by things like fuel control issues (fuel injector leaks, bad O2 or other sensors), transmission problems (won't shift into high gear, slipping, torque convertor clutch fails to lock-up), misfires (ignition related), low tire pressure, or dragging brake calipers. I recommend having a trained professional inspect your car in order to determine why it is getting worse gas mileage. From there, they will be able to help you move forward with any repairs needed.
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