There are many car smells. Some of them may be normal but others such as a musty car odor or car mildew smell can be a sign that something is the matter. The best way to eliminate the smell is to determine its cause, fix it, and then go about deodorizing your vehicle, as smells will become trapped in fabric. Some of the nastier car smells include gym socks, sulfur, rotten eggs, burnt paper, and a gas stations to name a few.
Most of these are related to a leak. If your car smells like a gas station then there is a leak in the fuel tank vent hose or the fuel injection line. This is very dangerous because gasoline is flammable. Many times if you have an old car, pre 1980, then this smell can be normal but for modern cars this smell is an issue.
Rotten Egg Smell
If you get a rotten egg smell when the engine is running, this is due to the compound hydrogen sulfide. There is a small amount of sulfur found in gasoline. When the gas travels through the catalytic converter, it will be transformed into sulfur dioxide, which does not smell. So if the sulfur is not being transformed and smells, then your catalytic convertor is broken.
Smells like Burnt Carpet
This smell normally occurs when you have been hitting the brakes very hard or have been using the brakes a lot. This burnt smell occurs when the brake pads become overheated. This can be normal if you have been going down a steep hill and riding the brakes. However if this occurs with normal driving then a brake caliper piston has seized which creates a dragging brake. You also could have left the hand brake or parking brake on.
The maple syrup smell is from a leak of ethylene glycol. This can occur when the engine has warmed up or if it is shut off. Ethylene glycol is very toxic and can come from several places, including an intake manifold gasket that has failed, heater hose, radiator hose, or failed cylinder head. If the maple syrup smell is very strong outside of the car, then you probably have a radiator cap that is leaking. If the smell is particularly strong inside the car then there is a problem with the heater core.
A Gym Locker
Most times the smell of an old gym locker is related to the air conditioner and heater fan. You probably have mildew growing in this system. There are several ways to get rid of this mildew but the easiest step is to turn off the air conditioning and run the fan on high. This will dry out your system.
You may get an odor of hot oil when the engine has warmed up. This occurs when oil has leaked onto the exhaust manifold, which is hot. This type of hot oil smell is very acrid. If the hot oil smells like French fry oil then you have a crankshaft seal that is leaky. You will notice the leak on the pavement under your car as the oil can spray all over.