No matter what, producing a lot of energy is going to cause pollution.
There's a couple different forms of pollution we can be talking about with gasoline- smog, which is a problem in certain areas (in particular LA), but usually we talk about CO2 these days. The thing is, CO2 just isn't the problem it's made out to be. Human CO2 emissions have had some influence on temps, but a much larger influence has been natural cycles. We see the same patterns now as happened in the 1930's and 1950's.
Now I don't want to derail this into a political debate on global warming. Even if you are concerned about global warming, the truth is the oil and gas industry are driving DOWN CO2 emissions, and by a tremendously larger margin than any green initiative we've seen so far. There's several reasons (for example economics, politics, etc) but the biggest one is natural gas. It is suddenly plentiful due to fracking, produces far less CO2 than coal, and it's replacing coal.
Here's the first article I could find on the topic:
In particular, look at this graph.... coal demand has collapsed the last couple of years:
What does this have to do with transportation fuels? well, for one oil & gas are usually found together. But the bigger point is: we can reduce CO2 emissions cheaply without replacing every car with an expensive hybrid or artificially constraining gasoline supply.