Ha. I wish these objects were more useful to know. I never use the word "petroleum."
I believe it is used for "motor oil" or "crude oil" instead of aceite, so it might not be that useless of a word. Like if you were having car trouble or were listening to the news about oil shortages.
From spanishdict.com (and I checked another one source). Oil - el petroleo. Gasoline - la gasolina. Crude oil is el petroleo crudo. Engine oil is aceite de motor. Diesel is gasoil or aceite diesel.
Of course, they are all petroleum products (productos de petróleo). I shall stick with these words.
Petróleo can be referred as crudo. In Spanish there is not "oil" with all the words, as in English. This means that, when used in Spanish "oil" (aceite) only refers to the lubricant type or the cooking one.
Genreally speaking, combustibles (fuels) are called diesel and gasolina, for diesel oil and petrol respectively. For heavier fuels, like heating oil and other ship grade oils (low refining) a general denomination is Fueloil and, at least for those living in the north of Spain, it can also be called "Chapapote".
When talking about "oils" aceites, there is the need to precise whether is for cooking or not.
Mineral oils are called aceites minerales. Lubricants lubricantes and of course you have aceite de oliva. The rest of seed oils can be made with aceite de + the oirigin
'gasolina' is pertrol/gas and 'petroleo' is petroleum; apparently these are different things. Who knew...
If I ever meet King Faisal of Saudi Arabia I might get to try this one out... assuming he speaks Spanish.