This is such an emotive subject. Myths abound. Engines do not fail for the most part because of the oil used, assuming it is appropriate to the engine. They do fail or burn oil unexpectedly because of lack of regular oil changes, general neglect of top-ups and of course stupidity which is not unknown. As for the differences in premium brand performance you would be hard pressed to measure the difference unless you kept your car for many years and thousands of miles and then only by reference to the dismantling engineer. Annual oil changes are the best insurance against calamity. History of your engine will play a significant part in its reliability and longegevity, for the reasons already mentioned.
For what it is worth I use Castrol RS 5w/40, this is a workshop brand available from the likes of Autofarm during routine service. It is like Mobil1, expensive but excellent in service. For those of you who prefer to buy from Halford and other DIY outlets the same product for that market sells under the brand Castrol Edge 5w/40 Sport. The difference is a marketing one and derives from garages general historical dislike of all things DIY .
As a fact of history the current Castrol products have their genesis in Castrol RS 15w/60 (the brand sold throughout continental Europe at the time) and its then UK equivalent Castrol Syntron X (now superceded in name). I know because I had a not insignificant hand in the UK launch of Castrol SyntronX. Those of you who remember the delightful late Bill Taylor may recall his racing 911 fully liveried in the maroon colour of that brand. The new lubricant caused a few complaints (par for the course in Porsche racing circles) because others claimed its synthetic nature released extra horsepower giving an unfair advantage. The distinction between various racing categories at the time was brake horse power. It did reduced friction amongst its other virtues, improved cooling etc. Mobil1 was the main competitor, a very good product but given to leaking through weak joints. The Jaguar and Sauber/Mercedes sports racing cars which won world sportcar championships used RS very successfully which included wins at Le Mans 24 Heures. So the severe racing credentials are not bad. In the past, reference to American Castrol brands could be confusing because they favoured the primacy of the GTX brand name. Just for historical completeness Castrol TXT 10w/40 brand of the time was a semi-synthetic. This brand was a workshop exclusive grade in Germany and it was sold in other european markets and subsequently in the States. Times have changed of course and I would not claim to know the blends of that brand today. As for GTX Magnatec, this comes in a number of offerings and is good. For the cost conscious owner an excellent choice. Again Autofarm also offer Magnatec 5w/40 for servicing. I have used it but prefer RS 5w/40 on balance. I top up with Castrol Edge 5w/40 Sport which says on the label it is approved for Porsche and replaces Castrol RS. Now I know Maurice gets very exercised about lubricant's grades and sensibly uses Porsches current listings as his bible. He must be politically correct in this matter. The reality is that when our cars were first on the road Porsche's approval list looked somewhat different. The cars haven't changed but opinions have and there are new products on the market.
The advice I give to myself is to use a fully synthetic 5w/40 engine lubricant, ideally from a premium brand manufacturer, Castrol, Mobil, Shell etc. I have no direct knowledge of secondary brands other than that is what they are. It is not uncommon for secondary brand manufacturers to buy a stock additive package from an additive supplier, like Esso, so to meet a international standard, but not all. However, they do not necessarily have extensive research and development facilities at which, year in year out, drive engines to destruction to find an optimum lubricant blend. The premium manufacturers do just this. Castrol's extensive reasearch centre is based at Pangbourne, Berks. Some of the scientists there have very tall foreheads which probably accounts for the good things that come out of that place. Even in this scientific age the best lubricants still have an eliment of black art to them. The ingredients are very important, but the balance between them is crucial, not to mention that extra unique component. Sometimes ingedients can work abit against one another. Strange but true. Balance counts. You would be hard pressed to find a bad engine lubricant nowadays. It is just that some are slightly better than others. Call me biased but I had direct experience of what goes on in this fascinating business. In short you pays your money and makes your choice. All else is mere blather.
Hanhams81
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