Distribution costs and taxes are more or less constant; refining costs can vary a bit more (in a mostly uncorrelated to oil way), so a doubling of oil prices would, all otehr things equal, lead to an increase of about 50% from today's levels.

But $4 gas does not quite fully reflect $130 oil yes, so you should expect gas to be around $7, probably, with $250 oil.

In Europe, gas is around €1.50/l now, so oil at $250 would presumably put gas at about €2/l.

In the long run, we're all dead. John Maynard Keynes