the recommended oil -15w-40. oil change interval 15,000kms oil works in its operating range with less changes to oil characteristics like viscosity, detergents etc. racing applications -imediatly we assume if its good for racing tems it must be good for the average joe.the oil used is of lighter viscosity to enable it to provide immediate protection,lighter means low friction =more horse power. but oil loses its characteristics very quickly. hence very frequent oil changes. ford didnt spend millions of $$ making cars to save a few bucks because they got a 'cheap deal'on 15w oil wholesale.its because 15w-40 overall works very well for australian climatic conditions. 15w-40 oil has more adherence property than a 5 or 0w oil.this forms a protective film between the internals for longer and prevents mechanical wear and corrosion. one of the byproducts of combustion is watervapor ,but corrosion is a slower process compared to mechanical wear. bottom line is if you takecare of your car and drive it under load to reach optimum operating temperatures (ever been to motogp and heard mobikes warming up long before the race?),and change oil regularly (which most inmates I assume overdo unless you are drag racing it or regular trackdays/race applications) the car should be good with semisynthetic, synthetic (actually is designed to last longer than semi synthetic which lasts longer in terms of properties than mineral) oil 15-40 or 10-40 if you want to, but going lower even with expensive oils can be detrimental to the engine. my 2 c.