Does anyone have any thoughts on MolySlip or any of the other MoS2 additives, particularly in the V8 with hydraulic tappets? At one time these were thought to be the mutts nuts but don't really seem to feature so much now. A trawl of the newsgroups only really warns of problems with synchro in gearboxes, but no news on the engine oil additives.
MTIA
As far as I can work out they will do little harm to engines, but less benefit. The additive only becomes superior to conventional engine oils when the normal lubrication breaks down due to excessive temperature or loss of pressure, which does not happen in normal operation. I have used them in the past for no perceptible benefit. JD
Must admit I've always been a tad sceptical about additives but I tried some Molyslip in my 90 V8 was quite impressed. Put some in the engine and there was no great difference except perhaps less reluctance to turn over when cold and a bit less top end noise. The LT85 box really did take to it well with smoother changes, less noise and better 1st to second when cold. This was all in a fairly low mileage 1989 90 V8.
The other one I have found to be good is Slick 50 Power Steering fluid - stopped my box leaking and worked better.
They can prop up a failing system but if your system is healthy then stick to the quality recommended oils.
So maybe worthwhile if you expect unusual conditions, such as belting down the Autoroute to Spain, but not a substitute for a proper service before the trip?
Yes, but belting down the autoroute is not the sort of unusual conditions where it would be an advantage, since in this case the normal oil will provide better lubrication than the additive. The point is, that molybdenum disulphide is not a better lubricant than a good oil, but will stand higher temperatures (above those where the oil is actually burning) and will stay on the surface if the oil supply fails, but in both these cases the lubrication will be not as good as normal oil supply. While the oil pressure is good and the oil is below burning temperature, the additive makes no contribution to lubrication. Where it woould be a real advantage is in conditions such as extreme offroading where steep slopes result in short periods of no oil pressure, or to reduce damage when you have knocked a hole in the sump. JD
Molybdenum Disulphide additives tend to have an accumulative effect with regard to coating surfaces.
If treatments are carried out to excess, oil feed holes can become blocked or severely restricted leading to bearing failure.
Hydraulic cam followers are manufactured to very close tolerances, and can have a tendency to 'pump up' and reduce valve clearances if the excess oil cannot escape through normal leakage, due to build up of the coating.
Viscosity modifiers like Wynns or STP are silicone based and do not suffer from the coating problem of 'Moly' additives, and keep the oil clean.
With regard to gearboxes, the synchro system relies on a certain amount of friction to enable the bulk rings and cones to match speed during the gearchange.
Anything that reduces this required friction will result in stiffer gearchanges, albeit with a slightly quieter box.
HTH
John
I have a vague recollection of a similar question some time ago ( might have been synthetic oil ? ) at the time someone mentioned capilliary action and the fact that it caused any minute failing in seals etc to be exploited by the fluid ??
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