Motorcycle Motor Oil

[Footy.]

I am going on memory know, but I recall reading in the Motorcycle Consumer News Part III Motorcycle Oil 2000 (I lost the article) that they tested the viscosity of used automotive motor oil from a Honda Accord after 3000 miles and found it had retained a large percentage of its initial viscosity rating (Good). Next, they ran automotive motor oil in a Japanese motorcycle for 1000 miles and tested the viscosity of the used motor oil. The results of the viscosity tests showed the automotive motor oil had significantly broken down and only retained about 60% of the initial viscosity. You want run 5W something around your engine?

As i understand the info, the big difference in bike against car engines, is the oil in bikes also serves the gearbox.

It is the action of the gears that breaks down the additives in mineral oils that hold the multigrade viscosity quicker. One advantage in the synthetics is they dont need so much of these additives, so the viscosity holds its spec for longer in bike engines/gearboxes.

When car engines started to use catalitic converters for emisions, they had to change the metalic anti-friction package in oils, as this "SG" spec oil contaminated the cats.

This SG spec was used in both bikes and cars up to that point, and this "old" oil spec is still seen as the best anti-friction spec for bikes.

When i bored my GS750E to 850, i used the "diesel" oil refered to during the running in period. Semi-synth and especialy fully-synth oils can cause running in problems in new bores because of some of the additives. The so called diesel oil is 15-40 turbo-diesel rated (CD) oil, that has an anti-friction package close to the old SG oil spec (diesels dont have catalictic converters).

After a 1000 miles i changed to a semi-synth 10-40 just so i could be more confident in extending my oil changes a bit when i go touring in the summer.

I think for our purposes it would be interesting it someone did viscosity change tests on our old air cooled bikes, with the "diesel" type oil and semi and full synth oils, so we got a better idea of the need to change milages.

Footy.

[hotspur]

SM grade oil is the latest to hit OZ. You fellas in the states would have had this for a fair time. It is getting harder to find SG oil with the higher Vis, Diesel Engine is fine but mainly only runs 15w-40.

The issue with majority of car and truck oils is that they dont have the fricton modifiers in them and the newer ones SL & SM and CI4+ in dist have the fricton modifiers to help reduce emmissions. Especially when the CI4+ is designed to meet European 100000km oil changes using a spinner filter. This stuff will glaze your bores very quickly.
Short runs which doesnt let moisture buildup etc burn off will kill the oil faster than the friction in the gearbox.

Some dist oils can be used in gearboxes, but these are mainly monograde oils.

I am lucky, in the BMW's I can nearly use anything I want, separate gearbox, Caltex Havoline Fully Syn 10w-50 is what I use in them. Western Queensland gets bloody hot.

I in the other bikes I am just using a standard 20w-50, changing it every 2000km. I get it a bit cheaper as I work for a fuel and lube company.

At the end of the day, you get what you pay for. Changing the oil is better than changing the engine