best oil to use in 1985 k100 rt

This is without doubt the hardest question you can ask. May opinions and successful uses of all kind of oils of all kind of types, but any oil in the 40 or 50 range is fine for normal riding. For my money, if you change it regularly any good brand will do, but if you forget you may want to venture to synthetics.

So:
1. any good motor oil. Your K has a dry clutch so you can treat is as a motor car and do not need to use special, friction-modifier free motorcycle oils.
See this. It is from an oil manufacturer who does not make a range of motorcycle oils. There are equivalents in USA: http://www.penriteoil.com.au/tech_pdfs/126%20FOUR%20STROKE%20MOTORCYCLE%20OILS%20UPDATE.pdf

Note the use of diesel oils. I am told that Shell Rotela (sp?) is highly regarded in the motorcycle community.

2. Here is where grey area is. People have their favourite oils and passionately defend the brand and type. A lot of us use synthetic or semi synth oils depending on the frequency of oil changes. Synthetics are used to keep the sludge at a minimum.

3. Others say "good mineral oils" and frequent changes (say 3000 km).

4. The book states 20w-50 or ?w-40 depending on time of the year. I it also depends on the type of riding you do, eg traffic is tough on motors and oil as are short trips (<20km? per trip). If you do a lot of short trips the best strategy is to change oil more frequently and use better than just any cheap oil. From experience do not use el cheapo unknown brand. I did this once and it turned into sludge in a few months.

5. I can only tell you what I do and the reasons:
a. I use diesel 5w-40 or Mobil 1 5w-50 in winter. High detergent values and good solvents will keep the motor clean and stop problems with starter clutch (starter motor). Also, 5W is great in winter.
b. In summer 15w-50 Mobil 1 (no longer available here), or any synthetic 50 oils are just fine.

No doubt many will tell you their strategy and they are all valid, but you may want to look at the places where they live. In my case Sydney (predominantly warm, like California) ?w-50 is good. Someone in Canada or North Europe may never need anything above 40 except in high summer.

Clear as mud? Yes? I can tell you that the reason for so many brands and viscosities is that the manufacturers are not yet able to make a perfect oil for all motors and climates. Also, car manufacturers put out all kinds of standards. I think that if it has BMW, VW or Mercedes approval and it has a correct viscosity... I am happy to use it.

Yea, what Ned said.

Yes, I agree with Ned. I've written a bit on this topic recently, please trawl through some posts if you are interested. I think the previous heading was "What oil for K100".
My field is in industrial reliability including condition monitoring and tribology (lubrication), so I guess I have a bit of a passion for this subject, but basically I subscribe to good quality mineral oils and regular changes at shorter intervals including filter. Also, something not often discussed is the issue of "lube hygeine", many failures are introduced as a result of people's practices and a lack of understanding of the need for cleanliness during oil changes.

Hi blackbetty,
This is not the best place to be asking oil questions under "Special tools & jigs" since not everyone will read that section.
Regards,
K-BIKE

K-BIKE wrote:Hi blackbetty,
This is not the best place to be asking oil questions under "Special tools & jigs" since not everyone will read that section.
Regards,
K-BIKE

Thanks K-Bike, This subject has been moved to the proper forum.