$3.42 is almost correct, you just need to factor in the tax/excise paid by the oil companies for the mark-up which is approx 17-18% (dont remember the exact figure). And it may deffer from state to state. Factor that in and you will get the correct figure.
To try and get around the tax problem from state to state I was using the gasoline figures posted as the National Average. Wouldn't that at least help smooth the quality of the calculation? Again, lots of good info posted. Best,