Not long if your in a city.The gas station here however you have all the time you need.
Don't even use vehicles, they are loud and attract zombies, also, zombies are slow, you can easily get away on foot.
If you're in a urban area like a city you would get overwhelmed by zombies when you went to fill up, and eventually we would all run out of fuel at gas stations.
that's a loving stereotype, if there were zombies they would most likely haul ass and be 3x stronger than your average human.
Zombie survival guide, myths and legends, page 5 - 7
Yes very true, when were out we are out.Use things like bike convoys or horses.
Still would get clogged up in the crashed cars because there would be so many. It may crush them but so many will be there you wouldn't be able to make it go on, or somebody got the same idea and you get stopped when there's another diesel truck, and you probably don't know how to drive it.
Horses can be loud with their hooves a lot of times and animals avoid zombies so you wouldn't have much success riding it where you want.
I would rather have a car than motor bike, cars are faster and motor bikes are louder and slower anyways.