Engine Oils!, 0w,5w, 10w,15w, 20w,X 30, 40, 50,60,??

Yep my sentiments exactly! i have recently gone to Caltex Delo 400 15w/40 for the diesel cruiser, appears to be a good oil, also it is J spec for the jap diesels. for lateish model petrol engines i use repco 10w/40 semi synth ( it is the same as mobil S or S2000 ) with no blending. as it is a few dollars cheaper per 5l pack to buy,but i buy 20ltr drums because our adventra uses 7.5ltrs per service and i service my olds Calais also so it goes quick. it is a very good oil also, the old VP we had on gas ran most of its life on it and at 350k it was still running like a clock and was not rattly at all. so its horses for courses, most oils now days are very good so you cant go to far wrong.

I saw a test studies done on synthetic and semi synthetic oils for petrol engines and they did all sorts of things like excessive heat to see the breakdown point and a heap of other wear type tests. If I remeber rightly the brand Purple that most high performance guys like came up trumps but is as dear as poison but what was very close was Penrite full synthetic and their semi synthetic wasnt too bad either and is a good price. Surprisingly Mobil One was just above average in the full sythetic range. They showed pics of all the test pieces for different brands was quite interesting.

I manage/ maintain a fleet of 60 diesel engine in powerstations in remote locations, engines average 1000hp, fleet is a mix of Caterpillar, Cummins, Detroit and a couple of MTU's, all are on Caltex Delo 400, 15w40 ( probably because they won the contract to supply). However oil performs well with no problems with engines

I give all the hype a miss. Just do what the manufacturer tells you.

I go by Toyota's recommendations - basically any diesel engine oil is fine. I use the cheapest 20litre diesel oil that is the right viscosity and API rating. Lately that has been Fuchs, and before that it was Gulf Western. But I've only done 140,000k so far.

If I had a different vehicle, I might have to use different oil. eg Jackaroo diesels need a 5W30, ZD30s need a 10W40 etc etc and the later common rail motors often need light oils.