I've just recently put diesel into a gasoline car. I realized this when I put the nozzle back. Then, I put regular fuel. I drove home for five miles and it was fine. I'm scared to go into the car now.
At least you didn't put gasoline into the diesel car. If you did and started the engine, the engine would blow up.
Diesel fuel is a lower grade fuel so your engine is probably going to ping. I'd advise draining your tank as soon as possible. If you don't have any place to do it, have a mechanic drain it out. You might need to have it done at the gas station. They can store the old diesel fuel with the oil and dispose it for you.
If this isn't done, over time it will clog up your catalytic converter. It isn't hurting anything in the short run but I would definitely drain it all out and change the fuel filter now, so you won't have any problems in the future.
If you need help with this, contact a certified mechanic who can help correct your fuel issue and replace your fuel filter as necessary.
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