Engine oil viscosity

[garr2]

Down here we can ride all year round and are now entering our summer riding season with ambient maximum temperatures of 30 to 40 degrees Celsius (approx. 85 to 105 F) not unusual. My owners handbook recommends SAE 20W-50 engine oil for these temperatures.



The BMW shop I frequent has in the past recommended and sold me a part synthetic 10W-40 oil. I have an oil change due soon. Should I stick with the shop recommended viscosity or go to the handbook recommendation, or doesn't it really matter?

[macx]

From my many years of hot rodding and motorcycling, as well as a heavy equipment owner, I would heartily recommend the 20W50. Especially if you do any idling in town at stop lights, etc, in hot weather.

And for a step beyond the viscosity, I would also heartily recommend synthetic.
It doesn't thin out (lose effective viscosity) as much when the heat builds as does non-synthetic oil. And they usually have a more robust additive package. Add to that the improved flow of a heavy weight oil on cold engine starts, and you've got the best protection available.

Air cooled engines are subject to more extreme internal heat than liquid cooled engines, and use the oil as part of the cooling system, so the oil needs to be capable of withstanding considerable heat without breaking down and losing film strength.

[harveyrawn]

We experience similar temperature ranges in Southern California. I've used Castrol 20W/50 in my bikes for 35+ years with no ill effects. With the R1150R, I extended my oil change interval from 3,000 to 6,000 miles per the manual.

[goomicoo]

Not too hot today! Raining in So Cal is nice but I'm already getting cabin fever. Maybe I'll go to the bike show in Long Beach.

[MoonBeemer]

www.amsoil.com/lit/g2156.pdf
The pdf file at the web address above outlines a study of motorcycle oils done by Amsoil. Scientifically, the study seems sound and unbiased. I think it is a good read for those of us interested in the lubricants for our motorcycles. Take care, Roger

[TicTac50]

We experience similar temperature ranges in Southern California. I've used Castrol 20W/50 in my bikes for 35+ years with no ill effects. With the R1150R, I extended my oil change interval from 3,000 to 6,000 miles per the manual.

+++1 for 20W50!
In South Florida it is a much hotter than in California, and I always use 20W50.
First 12k I go with the Valvoline 20W50 and then Amsoil 20W50.
The oil change interval for R1150R is 6k. I am using Synthetic Amsoil and always go up to 10k.
For my F650CS local BMW Master mechanic recommended 10W40.
He could not tell me in details why, but it has something to do with the wet clutch.
But, BMW Master Mechanic does not ride my bikes, I do. He also does not fix my bikes, I do.
When I drain the oil from my bikes, I know what to look for. In the BMW shop they never look.
So, I am still using Amsoil 20W50 without any problems and would highly recommend it.
I would stay with 20W50 for R1150R.
Good Luck.

[garr2]

Downloaded the AMSOIL pdf article and am now better educated about the demands motorcycles make on oils and the criteria for choosing between competing brands.
On practical note I have not been able to locate any retailer or distributor for AMSOIL products in Australia. The best I have been able to find locally is a synthetic oil whose viscosity is 5W-50 that I do recall being recommended by others in this forum. (You'll notice I'm trying my hardest to void another oil thread). Should I go with the 5W-50 product?

[jcridge]

Stay with 20w-50....
http://www.amsoil.com/storefront/aro.aspx

John

[garr2]

Gave up trying to track down a retailer or distributor of AMSOIL oils in Australia.
But I did finally find a distributor for Mobil 1 V-twin oil which came in second in the
above-mentioned AMSOIL analysis of 17 different 20W-50 motorcycle oils.

Thanks everyone for the guidance.
Have a good Christmas.
Ian

[garr2]

Finally managed to track down distributors of Amsoil products in Australia

[page62]

The Mobil 1 V-Twin oil will work just fine. Since the BMW has separate engine and transmission oils (not to mention a dry clutch), there is not the same concern about clutch lubrication as there is with wet-clutch bikes. Because of that, it's okay to use an automotive-spec motor oil (such as Mobil 1 or Castrol GTX), even if it has the "Energy Conserving" label.

In any case, the oil you choose is not the most important criteria...changing your oil regularly is MUCH more important!

[MattPie]

This is the short list of what (I think) I know about oil:
- Mineral oil starts with the first number, and use viscosity additives to help keep the oil thick when it heats up. Those additives break down over time. Also, the larger difference between the two numbers (5W-50) means more viscosity additives needed and will wear out faster
- Synthetic is the other way around: the oil is the second number, and the engineering makes it run thinner when cold than mineral oil. There's no viscosity additives required, so in theory the oil is more stable.
- There is a line of thought that you should NOT use synthetic oil until a certain mileage so the engine can break in properly. All I can say is my bike changed over at 12k and it burns a quart of oil between changes. Because the rings didn't seat properly? Maybe. Because I didn't run it hard enough? Probably.
- Water cooled engines should be able to use the same oil all year, since the water cooling and radiator fan will keep the engine temperature relatively stable.
- Air cooled engines have to worry about oil weight and weather due to heat issues.

I've run Castrol GTX 20W-50, Mobil 1 15W-50, and Spectro 20W-50 in my R1150R (current). All seem to work. Just make sure you change at the recommended intervals. I wasn't perfect with my Subaru, and now I have a rod-knock issue (big $$$, but at 187k miles I can't really complain).

I read this yesterday. I'm still digesting the info and some of it is contrary to common wisdom, but it all makes sense...
http://www.ferrarichat.com/forum/faq.ph ... s_articles