I've used it on a polished pump bowl and droop also valve covers.The pump parts came out great but i wouldn't recommend it for engine parts,the heat will make it fade over time and make it look dull.The bad is it bonds to the aluminum and is hell to get off.You can't polish it all you can do is wipe it off.I did get it off with a sisal wheel and the roughest polishing compound but it took a long time.So for engine parts i wouldn't recommend it but for parts that don't get hot it worked great.
also it it petroleum based and if you get gas or oil on it it will yellow.