All the fluids changed for limited use and storage here in winter. Castrol Syntrax 75W90 for the gear and rear axle and Shell Helix synthetic 10W40 for the engine.

It's only about 1500 km since the dealer supposedly did a minor service, including filters and fluids. However, since I found several screws and other bits and pieces missing or misapplied and the flilling plugs on the gear and rear drive needed a breakerbar to unscrew, one has to question the competence of the 500 lb. gorilla that did the service.

The question of oil recommendation: The standard 20W50 oil recomendation is apparently only available today as a "motorcycle" oil, where the friction modifiers have been omitted for use in bikes with wet plate clutches. Since the K has a dry clutch, my thought was that a modern automotive synthetic including the friction modifier additives would be preferable. It does not aseem to exist in that viscosity range. My favorite supplier, the local Sunico distributor has two candidates: 5W50 or 10W60 - both up to the latest API specs SH/CD for use in both petroland diesel engines and meeting a lot of various marque specifications like VW, Porsche etc.

There has been quite a discussion on this subject in Germany, where there seem to be a vocal preference in some circles for using standard 10W40 oil year round. I do not feel there is any difficulty with using the 10W40 here in witer - temps not over 12°C or 55°F. Summer temps here are rarely over 25°C and never more than 30.

So, what's the opinions here?

I drive my K75 with Standard 15W40 Oel in good Quality for the last 10 years. There was no Problem.


Motorcycle oil for wet clutches is very badly for the starter free-wheel.

I use semi synthetic 10/40. This keeps the starter clutch clean and as we all know this fails with plain oils.
Ajays

I used very simple supermarket 15W40 oil for about 15 years in my K75 of 1992, without any negative effects on the lubed parts (engine reaching about 170 Mm with this treatment and still running smoothly, camshaft steering chain slider replaced at about 150 Mm with only slight signs of wear on the old one). Accordingly I would support PeterKR's view.

In hot summer driving conditions (30+ deg C and low velocity mountain driving on crowded roads in summer Italy) I observed an increased mechanical operation noise, but without any observable technical consequences. Nevertheless I therefore changed to the suggested thicker 20W50 oil that I expect to raise the consumption slightly. I seem to observe a reduction of the offending noise recently, but the real tests under really hot conditions are still lacking.

Regards,

Peter

Only the best!!!!

15W40 mineral from the supermarket for 2,50 € per liter

No probs and the K has only seen mineral so far for 100tkm....

Don't fool away so much money!

Why? Are you getting it noch billiger? Or do you have a direkte Pipeline?

Ohh, I like it - another oil thread!

So, here is my input.
Starting with my K100 Basis ('84) up now to my K1200 ( K589 ) I used a standard, not a synthetic 20W-50, also according to BMW Users Manuals.
You are right, it's not easy nowadays to buy an 20W-50 without friction modifiers ( those JASO XXX specs).
I've found a mineral engine oil 20W-50, API CF-4/SH, which I think is available for a reasonable price, it's the "Addinol SUPER STAR MX 2057". Also my oldtimer car NSU TT likes it. So that's certainly another reason for me to buy it - two users. But both seem to like it.
I think also a 15W-40 would be ok for you, like many of the guys here prefer, also with regard to the moderate temperatures in DK.
Only once I used a 15W40 with my 1200 and promptly had some oil consumption. But concerning tempertures you could go with the users manual.
Anyway, if you had used a mineral engine oil so far it is not advisable now to change to a synthetic type. Synthetic oils have a stronger cleaning property, something like a detergent, and tend to detach particles from inside the engine. These particles are normally not dangerous, as long as they are not detached, but might cause problems with oil supply within small diameters of the engine's oil supply. Some of them might not reach the oil filter before. That is a least what some specialists claim. I never tried it myself, as it sounds quite plausible.

So good luck for choosing an adequate oil.

Decisions, decisions, decisions.......

I'll stick with the Castrol 70W140 for the gearbox and final drive. It makes logical sense and is current practise in many BMW professional shops.

The motor Oil will be a Sunoco synthetic Syntauro 5W50, which covers the recommended BMW specifications, but as a synthetic has a better viscosity index than the straight mineral oils - low vis at low temperature, while retaining the high hot temperature viscosity as specified. I buy this at wholesale pricing, so there is not much economic incentive to stay with the mineral oils. I do like the better detergency, and I am aware that the cleaning out of existing crap in the engine may require careful watching and early filter changes, but in the long run, keeping the insides clean(er) must be good.

I am also quite satisfied that the modern 15W40 oils would have been perfectly OK, but as there is no economic incentive, the 5W50 seems a better choice.

Thanks of all the input here. None was erroneous - particularly not the recomenndation of frequent changes being more important than the detailed viscosity specs.

Hello!
There was time I was able to find semisynthetic Motul 15w50 (one dedicated for cars, not motors). Though since I have discovered Gulf 10W60 full synthetic in price lower then Motul and much easer to buy (at my district), mine Brick drinks a new potion .

Best regards,

Amsoil sponsored a highly regarded series of engine oil tests. You can find this on the Amsoil website. Naturally theirs comes up near the top of every test, but what is interesting is to see how all the other engine oils fared, and to read the explanation behind every test.
Of all the oils tested, Mobil-1 consistently comes up second in the many tests. An awful lot of people's talked about favorite oils are dishwater when pushed for resistence to heat and sheer. Very few do everything well except Mobil 1 and Amsoil. Considering Mobil 1 can be had by the case at discount stores for not all that much more than the economy brands, for me the choice is easy. And, if I ever need oil anywhere, Mobil 1 is as common as the dirt it suspends, available in every podunk little town.

OP is correct that with our bikes there is no burning need to use an oil that meets JASO MA-1, but there is no harm in doing so. I happen to know the gent who redesigned the starter sprague clutch housing. He has a nice trophy from BMW for that little improvement. He was one of their techs in Research. He now has a shop over here and is building an interesting K-100/1100 hermaphrodite RT thingy for me. Hence, I know the reason why they failed in use. The presence or absence of friction modifiers in your oil has no bearing on why that part failed in service, and the cure my friend created will function just fine with either type of oil.
Interestingly that starter sprague came from a jet engine. The housing was solid and at high rpm, it packed full of oil due to centripetal force and could not drain out as as the oil entered it. If the engine was not heated fully each time it was run the oil could congeal and cause the spragues to stick in the retracted position. You'll also note that even failed sprages could be remedied by a period of hot running on fresh oil (put the bike in second gear and roll it backward and the spragues would grap, then put it in neutral and start the engine).
The cure was to add a pattern of holes in the housing to allow oil to drain out. No more problem. Friction modifiers in the engine oil have no effect. I do not for the life of me know where such rumors originate, but they are nonsense.
Of course the sprague never fail if you ride the bike regularly and always get it fully warmed. Just saying ..........

[quote="There was time I was able to find semisynthetic Motul 15w50 (one dedicated for cars, not motors"][/quote]

Our K's are car engines originally and French at that Rafal.

Ajays

themason,
I still feel guilty...I bought a K75s from a fellow who had sprag trouble and after taking it to a BMW shop he was told the cost etc of solving the problem. He told me he neither had the expertise or money to continue and offered it to me for a song.
I knew the problem and the simple way to solve it ... semi sythetic oil and a long fast run hot run...drain and refill and do the same again. I had no further trouble and eventually sold it for a hansome profit.
Semi synthetic for me.
I still feel guilty.
Ajays

Here in Hungary, you can get Mol Botond, a 20W50 oil for pre-1989, 'older vehicles'. Several of the vehicles from the time of the Iron Curtain are still going strong in daily use, put perhaps not thanks to that kind of oil.

No, nein, not true. It is a pure BMW design. When BMW was investigating the concept for the K bike, they built a test mule using a small displacement auto engine of French origin, I think it was 1.4 liters, quite large and heavy for a production bike of the era. That was a proof of concept vehicle. What went into production is purely a BMW design, with the shape of the combustion chamber more or less borrowed from the 3 liter six. The block had no analog at the time, a multi cylinder liquid cooled aluminum block with Nikasil bores. That hadn't been done before in any production car or motorcycle engine. The GPZ-900 used wet sleeves.

Look for a synthetic oil with an ACEA Oil Sequence of A3/B3 and you will have sufficient shear strength for flat tappet lifters such as ours. If you have a bike with a cataclysmic perverter you should use ACEA C3, which won't damage the catalyst.

http://www.acea.be/news/news_detail/ace ... nces_2010/

Read and learn. US SAE spec oils have had too many necessary wear additives removed to protect the catalyst from contamination, making them unsuitable for flat tappet engines like ours. If you notice, the car companies are now using roller lifters on even the most pedestrian engine to protect the camshaft from wear due to the paucity of anti-shear additives.
Alternatively you can buy a real dinosaur of an oil, called Brad Penn. It is a conventional motor oil, not a synthetic, with an interesting history. If you are American and hung out around circle tracks or any sort of hot rodding you are probably already familiar with Kendall GT-1 engine oils. It has, or had, a well deserved reputation for being a superb motor oil and it's what my first K bike lived on until oil standards changed and I switched to synthetics.
Some years ago, Conoco-Phillips bought the Kendall name, and now that oil is nothing special. Just another mass market oil. But, Conoco-Phillips sold Kendall's old refinery in Bradford, Pennsylvania, along with the superb feed stocks that the refinery used to make the original, minty green Kendall GT-1. Brad Penn is the original Kendall product by a different name. They will happily UPS cases of their oil to you if you just can't bring yourself to use a synthetic. Flat tappets will live fine with this oil. It has had none of the anti wear additives removed and doesn't meet the current SAE specs, thankfully. It is the only non synthetic oil I'm aware of using moly as a wear inhibitor. Just like Mobil-1 does.

Themason,
You will be telling me next that the F series is pure BMW and not Rotax...The "F" I had was definately a Rotax with BMW markings.
K designed from a Peugeot with modifications.
Ajays

[quote=The need for a quick development time scale of a clean burning four-cylinder engine and the fact that Honda had developed a flat-four boxer for the GL1000 Gold Wing,[2] guided the design team led by Josef Fritzenwenger and Stefan Pachernegg to an existing liquid-cooled Peugeot car engine."Ajays"]Themason,
You will be telling me next that the F series is pure BMW and not Rotax...The "F" I had was definately a Rotax with BMW markings.
K designed from a Peugeot with modifications.
Ajays[/quote]

No Ajays. You forget I have a personal friend who was in Research at BMW and who built and tested the prototypes of the original K bikes. The gent who designed the cylinder head had previously designed the head for BMW's 3 liter in line six. The rest of the engine came from the motorrad side of BMW. There is no Peugeot in this engine, though the two valve K bike injectors are shared with a 1.4 liter Renault engine used in the Fuego and the TPS is shared with some BMW cars of the era. As I said, a French car engine was used in the proof of concept vehicle but what was sold is purely a BMW design. Btw, there are no Peugeot or Renault auto engines with Nikasil bores either. That was a BMW innovation. Among car makers, only Porsche was using Nikasil and that was on the air cooled barrels of 911's, not a liquid cooled multi cylinder block like the K bike. No one had done that before.
I have no idea where you get your information from Ajays. I know a man who was there in Munich building the prototypes and testing them. I think he is a reliable source.

The F-650/G-650 series is partially a Rotax design. The head was designed by BMW and you will note it uses the same shims as our engines do. The equivalent Rotax engine used by Aprilia was a five valve design while the F series uses a four valve head.
The rest of the engine is Rotax, and it has been built in Germany by BMW, in Austria by Rotax for BMW and for a time in China, though most recently production moved back to BMW in Spandau.

themason,
I don't suppose you recall the Fath engine 4 cylinder flat that was built from a solid block of aluminium . and raced sucessfully by him in the late forties early fifties at Brands Hatch and elsewhere. I reckon that was one of the first. By the way, my quote came from "this site" and it is for all to see.

I know our engines are 100% BMW but it was concieved by the use of a french engine.
Never the less your knowledge is invaluable and I admire the fact. Keep smiling old chap,
Ajays