What happens if you put motor oil in your car what will happen?

I put an 1/8 of a gallon of a mixture of gas and oil into the gas tank of my 2008 Honda Civic and drove about 3 miles to a gas station. When I got to the gas station I only filled up with about another 2 gallons and then drove home. The car drove fine and I noticed no difference. How bad is this for my engine? If I drained my gas tank right now and filled it with gas would it be fine?

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