Many people have done it, or nearly done it—pulled up to the fuel pump and picked up the green diesel fuel nozzle instead of the black one and put diesel fuel in their gasoline car. A few miles down the road the error is immediately evident, if they don't notice before. Diesel fuel and gasoline are both products of crude oil, but so are kerosene and tar. Gasoline and diesel fuel shouldn't be confused any more than gasoline and tar. If you do put diesel fuel into a gasoline engine, you will have a repair bill and a wasted tank of diesel fuel, but the damage is not permanent and is relatively easy to fix.
A car designed to run on gasoline that has been filled with diesel fuel will still start, usually. It will run for a little while on the gas that's still in the tank. Then the smoking will start. It will produce a lot of black smoke and smell like diesel. If you haven't figured out the problem yet, this will probably clue you in. The engine will start "missing" or not running smoothly, then just stop running when enough diesel has been cycled through it.
The major difference between gasoline and diesel fuel is the combustion ratio at which each will explode. Gasoline engines are designed to use a spark (from spark plugs) to make the mixture of gas and air explode. Diesel engines use combustion alone because they produce enough heat, thanks to the higher compression pressure, to explode without an external spark.
It's because of this that gasoline and diesel engines are designed differently and the two fuels are not interchangeable. If diesel fuel is added to a gasoline engine, it will foul the spark plugs out because the diesel is too oily. Since a gasoline engine relies on the sparks to make the explosion that provides power to the engine, when the spark plugs don't function anymore the engine can't create the combustion necessary to run the car and the engine will quit.
To fix the problem of diesel fuel in a gasoline engine the tank, lines and engine need to be drained and cleaned. If the car wasn't started after the diesel fuel was added you will need to drain only the tank and add more gasoline. The car will smoke a lot, but as long as you get nearly all the diesel fuel out of the gas tank it should still run, though not well. If the car was started after the diesel fuel was added, and run until it quit you will probably need to drain all the lines, tank and engine and clean or replace the spark plugs.
