I personally highly doubt that there is any correlation between fuel prices and online sales.
Let’s face it; fuel prices really aren't as high as they could be. Mega B is right; the prices in Europe are much higher than in the US. People freak out about paying a couple extra dollars per fill up, relax. If you are that concerned about it, then do something about it, don't rely on others to fix it for you. This is how
successful entrepreneurs and business people are created.
If you calculate the numbers, I'm sure the gas it takes to go to the mall is still cheaper for most Americans than the shipping costs for buying something online. Most online purchases are spurred by convenience or it’s an item that can't be found locally.