Im sure this has been asked a number of times but i have searched and find mainly people saying 15/50 or 20/50, which is fairly standard in the states and other hotter climates,

I have drained all the oils and am topping up now so just wondering if anybody would know if 10/40 will be sufficiant for the engine in the UK?

Cheers

I use Castrol "T4" oil because it is thought to have a better level of Zinc which is called for on the K engine.
I use 10W40 weight. I would think it is appropriate in most any climate. I am in a hot weather area, Phoenix, AZ.

You will find as many different opinions on the best oils for K's as there are days in a decade! Seems like everyone has their own ideas about this.

As a side note: a lot of people think synthetic oil is the only way to go. I personally believe that modern petroleum oils are so good, that synthetics are just not warranted for the extra money.

I do have a different point of view however on Gear oils where Synthetics are superior.

Just my opinion.

Not sure if T4 is available in the UK. I use 5/40 in mine and I am in the south of France.
A full synthetic will resist any problems with much higher temperatures than a mineral will and over here it costs very little.
Don't let anyone tell you that the K was designed to use an old fashioned 20/50 mineral as it was not. Two bits of metal rubbing together are the same in a brand new BMW as they were 25 years ago, it is just the oil technology that has changed. I don't know of any engine that was designed to suit the oil that was available at the time it was built.

Well, Ok Bikerboy.

Some popular opinion shows that newer oils (Grade SJ and above) were formulated with considerably less Zinc than the oils that were in existence when the K100 was designed.
I am not an oil engineer, but I was of the belief that after the introduction of SJ & newer formula specs in oils that BMW recommended using only oil that did not meet the SJ requirements because they did not contain as much zinc as BMW believed was best for this design.
It is true that synthetics can withstand higher temperature without deteriorating than petroleum based oils, however the type of service that water cooled automotive engines run in never come close to approaching the temps that severe. I am glad you buy synthetics at a competitive price where you live. Here in the USA, they are generally twice to three times the cost of conventional oil. Great protection, just un-necessary.
Also, I would not recommend using 5w anything in an engine of this vintage as it was not built with the tight clearances of the modern day emissions requirement mills.
I think that 5W's and 0w's multi vis's would probably only be appropriate for engines designed after about 2005.

We cold talk about this forever and no two folks will ever agree fully on the subject.

Mine is just an additional point of view, not an engineering study.

Regards, Ibj...

We all have opinions and it is not for me to correct anyone else because my opinion differs.
A couple of points though. The Synthetic that I use is indeed API SL which is higher than SJ, but without seeing antything in writing I would doubt that BMW has said this. This is down to my Aircraft engineering background and that has taught me to believe nothing until you see the official instruction in writing.
The 5W part of the oil is only the viscosity when it is cold and that is actually thicker than the 40 or 50 number when it is hot believe it or not. What a 5 W does for you that a 15 or 20 does not, is circulates around the engine much quicker at start up. By the time I have ridden half a mile then it will be warm enough to be a 40. Most people know that the most wear in an engine happens at start up.
The maximum oil temperature tolerance of watercooled engines can easily happen in modern vehicles. My 1981 Golf GTI had an oil temperature gauge that showed a maximum of 120c, but mineral oils were all that was available then, and I did get close to that temperature many times. My aircraft uses a watercooled 100hp Rotax 912s and I have to use synthetic in that as that too gets to more than the safe maximum for a mineral oil. If you have an oil temperature gauge on a bile then it may show that the oil is only at 115c at the sensor tip, but I would bet that in some parts of the engine it is much higher than that, and way beyond the limit.
This is all my opinion based on my training and experiences, so it is not meant as a dig at anyone else.

Although the Hemming's motor news is not an engineering authority, this article sheds some more light on the subject.



http://blog.hemmings.com/index.php/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/

If aircraft were intended to have horizontally opposed piston engines........Pratt & Whitney would have built them that way!........LOL

FYI:
http://bmwscotter.org/topics/engine_oil/engine_oil_references/sj_engine_oil_in_bmw_motorcycles.htm

ibjman wrote:If aircraft were intended to have horizontally opposed piston engines........Pratt & Whitney would have built them that way!........LOL

P & W? Don't forget that the Jet engine was a British invention. :-)

Thanks for the sight of the service bulletin, there is no way that I can argue with that. I do wonder why it has "For USA Only" on the top. The only difference between US and Euro models is the cat and other emission equipment as far as I know.

I believe this was before motorcycles had cats????

SB is dated 1998 and I think that the K1100s had cats fitted. My K100 16v has not, but it is a UK model. I note that the SB is signed by the US after sales manager, and being marked USA only then it must be fine for us in Euroland to use any oil SJ or above.
At the end of the day, by using my 5W40 synthetic API SL, I know that I will not be able to claim on the warranty in the US, (if I am ever there again) on my 22 year old bike. I don't think I will worry too much.

I have always used mineral based 15/40 in both my K's and it seems to give good performance and reasonable longevity.

The short answer to the original question? = Yes.

interesting game of literary tennis there chaps....my opinion ....just change whatever oil you use regularly....if its really cheap and meets the standards its just as good as the really expensive stuff that meets the same standards......one thing I can say is that high detergent oils such as those designed for diesels but able to be used by petrol engines keep the engine and starter very clean.....which is a double edged sword when considering a high mileage( I know its mostly kilometres but kilometreage sounds ridiculous) engine which if run exclusively on mineral oils will now most likely leak and rattle.

happy riding all.....

On ya Klompy.

+1

Pick and oil you think is right for your climate and stick to it.

Change the oil and filter often.

indeed klompy .....wise words cheers !

Cool 10/40 it is!
Thanks for the help and the useful information

Any oil is better than no oil!