After overhauling the engine of your classic car - the job in particular due to the winter weather may soon be longer than expected - you have installed everything again and yes, it runs again. With effort. Pop, pop and then it's silence again. Repulsed. After frantic attempts, you get the machinery running again, but the engine is still running very bad. Doubts take over you, are the spark plug cables connected in the correct order, the dots are not too close, the inflammation on time, does it get enough gas, are the valves not too tight? Everything appears to be set correctly. Try again, the engine is still not running better. What would it be? Very annoying, that's for sure. There is only one solution: drain the tank and fill it up with fresh gasoline. After half a year, today's fuel is of such quality that 'popping and popping' is the result ...