Oil or more specifically engine oil is a very complex thing these days and is a nightmare for the average punter to work out which oil offers best value for money.

There are essentially four types of engine oil namely:

1. Mineral oil - (conventional base oil derived directly by refining crude oil);
2. Hydrocracked oil ? (extra highly refined base stocks);
3. PAO oil - (pure synthetic hydrocarbon SHC); and
4. Ester based oil - (fully synthesised from a reaction between acids and alcohols).

The more you go down the list from 1 to 4 the better the performance of the oil is but also the higher the price is.

Whats more important is that you should remember that IMHO opinion there is no such thing as a cheap synthetic engine oil.  Hydrocracked oil which is a very high quallity mineral oil can be marketed and sold as synthetic oil so you need to be careful when making your oil choices.

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