I belong to various car and motorcycle forums, and the subject of oil, or to be more precise synthetic oil, must have occupied more attention than any other subject. It has also generated more heat than light, and an awful lot of half truths and cod science.
I used to use Mobil 1, until two things occured. A. it got hugely expensive, and B. they introduced various different weights which initially confused me. I then discovered Halfords own brand oil (which of course is made for them by a major brand) and started using that. At present I tend to use Halfords fully synth, or their part synth in the 968 and before that in my 924S, and I like it. Being modestly priced, I tend to change it more often as a result, and fresh oil is the best oil.
Last year I entered into a long debate by e-mail with one of the technical boffins at Mobil. It centred around whether or not I could use fully synth in my Harley (but that's another story). What I did learn was that the weight of oil that best suits your engine has a lot to do with the width (or narrowness) of the oil galleries in the engine, and that as a rule of thumb, the older the engine, the larger will be the oilways, and vice versa. The most modern "thin" oils work best in modern engines with narrow oilways and high pressures. To take a Harley V-Twin as an example, this runs on fairly low pressures, but a high flow rate through comparatively large oilways, so a heavier oil works best. Mobil have launched a version of Mobil 1 (in the USA only) in 20/50 weight, specifically for this task. To my great annoyance, they do not sell it in the UK.
The basic design of the 968 engine goes back to the 80's and the 944, so in my view it is not a particularly new engine, albeit not an antique like the Harley. Using this rationale, I stick to good quality synth, ot semi synth, but avoid the really low weight "thin" oils. I also read somewhere just the other day (in 911 World maybe) that the oil boffins reckon you should use a slightly heavier weight of oil as engines get older.
John H
