In the USA, almost none of our electricity comes from oil. About 50% comes from coal, a bunch from natural gas and nuclear, and then a smaller fraction from hydroelectric and other renewables. I think you’re confusing gasoline with natural gas, which is much cleaner.

Even when most of our electricity comes from fossil fuels, electric cars still produce lower emissions than gas cars because they’re so much more efficient. See the link below for details.

Although even then coal power plants are more efficient than the average car engine and can also afford to have much better pollution control equipment than what can be fitted on a car along with being able to disperse the pollution up high (and hopefully not downwind of any population centres).

In the long term we’re going to have to switch our source of electricity away from fossil fuels, probably mostly towards nuclear so we’re going to have to solve the problem of CO2 emissions form our power plants anyway (and the alternatives to electric cars would require a lot of energy be used to manufacture fuel which would probably be made using heat from power plants). Electricity from fossil fuels is the biggest source of excess CO2 emissions and so is the thing that we should be directing most of our attention towards replacing with cleaner technology.

This is mostly because large powerplants which burn gas are 3 times as efficient as the gas burning engines in your car. Car engines operate at a variety of speeds, overheat, and in general have poor performance compared with large, stationary, efficient generators. Power stations can also transmit that energy with little to no loss through powerlines into your car battery (if only a cars transmission was that efficient).

It’s not as simple as you like to put it: studies have been conducted that show that even if an electric car receives its electricity from a coal powerplant, it produces less pollution than an internal combustion engine running off gasoline.

That’s why we bother.

Additionally, hydrogen will become viable at some point. A lot of advancements are being made now in hydrogen generation and at that point, hydrogen full cells become very viable and with a car like the Volt, taking the small engine out and replacing it with a fuel cell becomes pretty easy to do.

Solar or wind power are not YET viable alternatives but solar power technology has evolved a lot in terms of efficiency. In the mean time, hybrid cars and public transit are a good alternatives for lessening our ecological footprint.