OK...this may sound weird, but I had a dream last night...

A friend pulled up at my house with his pickup truck towing a tank of
home heating oil. He said he needed some gas for his pickup. I went
into the backyard and grabbed the gas can I use for my lawn mower and
brought it up front. Instead of pouring the gas into his truck, I
poured about a gallon into the oil tank.

It wasn't my fault, the cap on the oil tank was open.

2 questions:

1 - How bad would it be to have a gallon of gas mixed with, I don't
know, let's say 100 gallons of home heating oil?

2 - What does this dream mean?