I actually think gasoline would be plentiful.
You are talking about 90%+ of the US population no longer using it because they are infected/dead. That means a ton of gasoline just 'laying around'. Cars, gas containers, lawnmowers, farms, gas stations' underground tanks, etc. The hardest or most dangerous part would not be locating it but actually retrieving it.
For fun, Im thinking about my house. There are 3 cars, 3 5 gal containers, and a snowblower (I live in Ohio so the lawnmower has been drained for the season.) Given the levels in the cars (1/2 to 3/4s of a tank), there is probably 50-60 gallons on gas in this house alone that someone could salvage. Hell, there is even a little bit of race gas!
I think everyone managing to survive the epidemic would become extremely proficient at siphoning. lol