What happens if you put the wrong gas in a car?

I tried to be nice by filling up my dad’s car after I borrowed it, but I admittedly bought the cheapest gas at the pump. When I mentioned I had gassed up, my dad checked that I had used “premium” fuel. I lied and said yes! What could happen if I put the wrong type of gas in his car?

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Answer provided by
Laura Salvas
Answered on May 05, 2022
While using the wrong grade of gasoline may cause at worst a minor nuisance, the wrong type of fuel can cause a major disaster. Here’s what happens if you put the wrong gas in a car:
  • High octane gas in a car needing regular fuel: Nothing bad will happen, but you’ll have paid more for no reason.
  • Low-octane gas in a car needing premium fuel: The car will still operate potentially with significantly reduced power.
  • Diesel in a gasoline vehicle or vice versa: Do not start the engine or turn the key. This will send the wrong fuel through the engine and your repair costs will skyrocket. Call a mechanic immediately as all fuel will have to be drained and cleaned from the vehicle.
Car engines have different levels of compression. Most cars use regular compression in their engines, so they run on regular-grade gasoline. But engines with higher compression operate better with a higher octane fuel, meaning they should use mid- or premium-grade gas.
Generally, cars operate on one type of fuel, which is noted in the owner’s manual or inside the fuel door.
Diesel is thicker than gasoline and toxic if put in a gasoline engine. Likewise, gasoline is too explosive for a diesel engine to manage. It’s difficult to accidentally put diesel in a gasoline tank as diesel pumps are seperated from gasoline pumps and the nozzle is too wide to fit your car.
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