Carbon Dioxide of course!
methane
If it's a fossil fuel, then the gases produced are mainly CO2 (carbon dioxide). Other gases include sulphur and sometimes methane
Electric cars reduce the amount of fuel-dependent cars on the road. As more electric cars are produced, the US will need fewer barrels of gas.
carbondioxide is the gas produced
When polyethylene is burnt carbon dioxide and water vapors are released.
Hydrogen Chloride
gas cars - I assume you mean LPG. This is a by-product from oil well-heads and used to be flared (burnt) off. Then it was realised it had a value as an auto fuel, especially when energy porices went up - spud
Carbon monoxide.
If you acheive perfect combustion then only CO2 and water are produced. If there is not the right ratio of fuel to air or if there is other substances in the gas then you could end up with carbon monoxide, oxides of nitrogen, or sulfates that produce acid rain.
obviously gas obviously gas
Hydrogen gas
All cars would use compressed air (or nitrogen) to inflate tyres. Most cars would use petrol or diesel as a fuel (in the US petrol is known as gas). Some cars use Propane gas as a fuel. Technology is being developed to fuel cars with Hydrogen gas.