When I actually calculate the gas cost for a trip in a car, I am usually surprised at how large it can be. I wouldn’t be surprised if the $3 actually is less than the gas cost for many affected commutes.

However I think you are probably right that it won’t make much difference for a single week, since I think people tend to ignore this cost. Filling up the tank is infrequent enough and part of a routine that imo it doesn’t feel like a marginal cost and feels more like a fixed cost of car ownership