Gasoline cars are far more popular compared to diesel cars because they have a nippier engine and are a lot less noisy. Although diesel cars give better mileage than gas, exhaust spewed by diesel cars was considered far more polluting than that of a gas engine. A diesel engine has more torque and is suitable for large vehicles.
Both diesel and gasoline in refined form are derived from crude oil at different temperatures and this is why their basic molecular structure varies greatly.
edit Compression ratio and Spark plugs
In the internal combustion engine of an automobile, both diesel and gasoline are burned in a different way so as to provide power to the vehicle. Gas engines have low compression ratio and use spark plugs to ignite the fuel. Diesel engines generate more heat because of higher compression ratio. As a result, there is no need of spark plugs to ignite the fuel and air mixture present in the engine.
edit Other Equipment Necessary of Diesel vs Gasoline Cars
To be functional, a gas engine requires an electric coil, distributor, and an alternator apart from the spark plug. A diesel engine does not need any electric system, except when it needs battery power to start up.
"Diesel Cars vs Gasoline Cars." Diffen.com. Diffen LLC, n.d. Web. 30 Jul 2014. < http://www.diffen.com/difference/Diesel_Cars_vs_Gasoline_Cars >