Originally Posted by farqhuar
the third part where I state that ALL oils available today exceed SF/SG ratings.
I can assure you that all three of these statements are correct.
Check the Mobil site, for example, where it states "API ratings are backward compatible to previous generation ratings. This means that an API SM quality oil, which is the latest API rating, is recommended where API SL, SJ, SH, SG were originally required".
Yes, you are correct in stating that Zinc Phosphorus levels have been reduced in recent years, HOWEVER, this is only an issue if oil is used for extended periods (i.e oil changes every 15,000kms+) which may occur frequently in cars, but I would suggest very rarely in bikes where oil change intervals greater than 10,000kms are virtually unkown.
I will repeat the rest of my posting.
"SG is the higest rated oil of ALL oils with 0.12% of zinc allowed. After this ALL grades of oil contain less in order not to affect the sensors for engine management systems.
Worse still is that any oil rating is the MAXIMUM that it WILL NOT reach. So an oil can have no zinc and fully comply with SG, SF SH SL and all the rest because it has LESS additives than the maximum allowed by the rating.
As an aside, an oil which has 50 in its weight is excempt the maximum figure for additive concentrations as these oils are designated for old engines without engine management systems. So a 20/50 oil MAY contain any amount either less or more than the 0.12% allowed by the SG specification. BMW oil (20/50 dino) used to contain over three times the 0.12% Harley Vtwin oil (20/50 dino) still contains more than twice the SG rating."
So I will ask you,,, what oil is allowed MORE additives than SG only oil?
The answer is none.
Modern oils "exceed" SG requirements by having LESS additives ( partictularly zinc or zinc substitute).
This is also why the 0.12% limit does not apply to nn/50 oils, as they are designated for older engines as modern oils WILL NOT lubricate them properly.
Again Oil ratings are Maximum ratings which they cannot exceed. ( to protect sensors)
If oil was petrol you could sell paraffin as 100 octane fuel, because its octane rating is LESS than 100. This is the opposite of every other rating system I know where the standard has to meet or exceed. Oil has to meet or be LESS than. This is why 0.12% zinc is the Maximum for SG. ).10% is the MaXIMUM for SL. from there on it gets worse.
If you run a modern SM ? oil in a flat tappet engine, I doubt very much your camshafts will last very long.
I think here we may both be guilty of being too focussed on a particular segment. Much of what you say is correct for modern Japanese bikes. I have never owned a Japanese bike. My own focus is elsewhere and for that your perceptions are incorrect. I was trying to point out that making wide sweeping statements could cause someone (with an older bike) to make a serious error. As far as I am aware most Jap bikes tend to rev high and have wet sumps, in a way these two go together for at high revs much oil needs to pass over any white metal bearing to keep it cool. these are usually the big ends. A wet sump allows for higher oil flow rates. These engines also need thinner oil in order to make the flow rate but also need the high flow rate to maintain pressure. This makes their oiling needs different. Modern oils tend to be available in thinner grades than are suitable for older type engines. They also are deficient in zddp or its equivalent.
Last edited by oldbmw; 21 Dec 2009 at 20:53.