Yes, it is supportive of car sales, but it is probably also promoting fixing cars and buying used ones as well. I think people really should invest in cars that are hybrids instead of going out and wasting gas money like crazy. It is terrible for the environment and earth.
When people are saving money on things that they need it leaves room to buy things they want. Since gas prices have dropped to nearly half the price we were paying only a couple months ago, it puts extra money back in the consumers pockets. That extra money is burning a whole, and they want to spend it on something therefore they purchase new vehicles. Another good point is that with gas prices being slashed the way they have, a lot of people may be buying a larger vehicle because it no longer costs so much to drive.
Humans are very short sighted and news outlets have been gushing about lower gas prices and people have been going out to buy less fuel efficient cars because of it. These gas prices are not going to stay this low, only long enough to reduce competition and possible hurt a few key countries. But yes, lower prices have fueled car sales.
Low gas prices help car sales because that makes it more affordable for people to use cars, so it is simple math and it is in fact good for the economy when more people produce and buy cars and are able to use them. So yes, low gas prices have this effect.