Some useful information regarding oil for use in a bevel Ducati - James DeRave - home

James was too unassuming to post this, but I did it any way, sorry James

Multigrades work by taking a base oil and adding stuff that reduces the tendency to thin out with increasing temperature - i.e additives that improve the viscosity index (VI improvers) They are long chain polymers that are curled at low temperatures and unravel with increasing temperature

In some research I did years ago in SAE transactions I found that these VI improvers are subject to physical damage - loaded, sliding metal surfaces can cause them to break, and the affect of them reduces over time and the oil gets thinner at high temperatures. I suspect shear stabilisers may have some role in reducing this affect

A monograde oil has no VI improvers and this whole thing is moot. There is no mechanism I am aware of for it's viscosity to reduce with use. I'd look for detergents - it's bad to put a detergent oil in an engine that has been run for a long time with non-detergent oils (specially without full flow filtration) as the crap deposited on the internals will get into suspension and pumped round. Reverse does not matter and switching often between detergent and non detergent does not matter.

Oils for gearbox use also contain extreme pressure additives - molybdenum disulphide is an EP additive that you use as a build lubricant to provide lubrication before oil is pumped round. They are intended to prevent metal-metal contact even if 2 surfaces are pressed together till all the oil is squeezed out (e.g. gears) and work by bonding to the metal surface

My opinion fwiw is that any decent monograde of SAE 40 or 50 will be just fine and if it is specified for use with gears that's even better, and I'd personally go for one with detergents.

Development of oils is all about trying to extend service intervals. Changing at 1000 miles means none of the affects people are working to eliminate are significant for a bevel (apart from VI improver shearing) and probably the biggest problem is clutch wear - it wears slowly for sure, but particles of friction material get added to the oil every time the clutch slips, and the only place they go if they don't stay in suspension or get trapped by the filter is the sludge trap.

So, as the bevel mantra goes... any decent oil, changed religiously!