Why did my gas mileage suddenly drop so much?
Removing a bad catalytic converter and switching to lower-quality fuel can cause a dramatic decrease in gas mileage. This leaves drivers getting poor fuel economy on 4-cylinder engines and struggling to figure out whether the drop is a normal sign of age or a mechanical issue requiring repair.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1keeping up with tire pressure
- 2using an O2 spacer on the downstream sensor
- 3adjusting timing by loosening and turning the distributor
- 4replacing worn spark plugs, fuel filter, distributor cap, and rotor
- 5testing various brands on a consistent daily route
- 6switching to alternative gas station brands like Shell, 76, or Chevron
- 7buying a bottle of fuel system cleaner or solvent to run occasionally
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“for my past couple of fill ups I have been getting 12-13mpg, granted it was about half city/highway driving but I feel like 13 mpg is pretty bad for it to be a 4 cylinder.”source ↗
“I’ve recently had the catalytic converter removed and everything welded up due to having a bad cat.”source ↗
“Is what I’m experiencing completely normal for a 25 year old car. Or is this maybe a sign to a bigger problem? And how do I go about fixing it”source ↗
“i swear every time i fill up at arco the tank seems to disappear faster than when i use 76 or shell.”source ↗
“There is a difference in mpg with some being terrible.”source ↗
“arco always feels like it goes quicker.”source ↗
“I have been getting very bad gas mileage and I don’t have a check engine light on . Is there anyone out here that can give me some advice what can be?”source ↗
Where this came up
People with this problem also raised
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