xt frog the dissapeared post was by me late last night and a bit tipsy when I re read it it did not come across right the way I had tried to explain the dynamics of oil science - looked great after a bottle of red wine though ! so anyway i deleted it so that some clever fart did not come along and rip me to bits. But seems you got the jist Synthetics flow under very fine surfaces where mineral oils cant get namely under seals and piston rings on older engines with tolerences far larger than modern engines are built to. Synthetic oil used in bikes like bmw airheads can weep through the rear crank seal and get onto the dry clutch so I suppose if it can do that it can get into other areas that should be dry of oil having done so you record a loss in the sump. Mineral oils rule for older bikes. Add a seal improver additive evry 20,000 miles and this helps swell the seals - something the old oils used to do but cant any more as the additives are not regarded as nice for the world outside of your engine so they dont put them in anymore. jake.

Thanks for the explication Jake - good to know I wasn't going mad after all!

(your original post read just fine to me, btw)

Just to add my two cents worth of contrariness- changing oil every 3000 km or less is a waste of money unless you are running your bike extremely hard , as a racer , or in extemely dirty conditions. Or if you only ride 3000km in a year.
Under normal riding conditions modern oils are quite good enough to serve for more than 5 or 6 thousand km .And I have found there is no need to obsess about the debate over whether regular oil , synthetic or semi synth is better. They are all rated with the letter system, SG being hard to find now as the code has already progressed to SL and SK . So a synth oil rated as SL is guaranteeing that it is just as good as , but no better than , a regular SL oil. But , hey, they are all oily and work fine if you stick to the viscosity ratings recommended for your bike.
How do I know this? - from 42 years of running all my bikes on any oil I could find within the viscosity and close to the class rating recommended. The famous brands as well as any store brand which was at hand when an oil change was needed , anywhere up to 9000km intervals. I have run a 1994 airhead BMW R100 like that and after 273000 km the motor was still running well with no smoking , only once replaced the pushrod tube seals because they shrank and dribbled oil like my old'66 BSA 500. Likewise I used ( abused some will say) BMW R65 , R80 , XL600 Honda,CB350F,CB400F,XJ750 Yamaha,XJ600, and others and currently a KLR650 and a BMWR1100 now with 224000km on it.
Never in 42 years have I lost an engine because the oil failed to do its work. The trick is to keep oil in the bike! Dirty oil or cheap is better than no oil, and the store brands are just a s good as the stuff from the multinationals because it is made usually by those same big corporations, just the bottles are different.Same goes for oil branded by the bike makers- they don't have oil wells- they just order a batch from Shell, BP, or Exxon-Mobil etc.etc. . Sure there may be minor variations in the formulas but they all work satisfactorally.And isn't it funny to read on an oil containeer label that it is designed with " anti - wear " properties? Gee, why else do we pour in oil.?

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http://advrider.com/index.php?thread....207964/page-5 then scroll down to post #93

hi guys thanks for the comments ,my 43f is due another oil and filter change soon , so i think i will stick with mineral changed very regualy , its worked fine so far ,and my old zed with 92,000 miles on the origanal untouched motor seems to agree. thanks jake for your comments about synthetic getting past seals etc . a couple of my mates have the jap home market srx 600,s the motor basicaly a xt 600e both are on semi and use more oil than i like and my xt uses vertualy nil . so thanks again , and please keep adding comments , pandorers box is proving very interesting . takecare zigzag

WHOOPS... Forgot myself there... I have to say I had old Triumphs and BMW bikes in mind

If you have a high tech "white goods" bike with the gearbox gears chewing up your engine oil, you will have to run with synthetic oil unless you want to chang every 1500/2000 miles.

and if you have EFI, and or catalytic converter do not use 20/50 SG rated oil. The anti wear phosphorus/zinc/calcium will knacker the sensors. Also with these engines, they generally need higher flow of oil to lubricate and cool so generally run with thinner oils.

just a footnote bmw have stopped selling the very high quality sg oil so i am using castrol act>evo gt t4 20/50 this is actually rated as a SG rating - not a higher rating oil that includes the sg qualifier. might be of interest to someone. But I have to agree with Mr Bakker that largely oil of the right type should do the job fine dont pay loads extra for something your engine does not need, almost all oils have to meet minimum spec thats noted on the container and if it meets the spec of your bike it should do the job. Jake.

This is exactly wrong. Sg rating guarantees it will have less than 0.12% anti wear additives. For SF/SL grade the limit is 0.10% Ie they guarantee the oIl wil not exceed the stated grade.
This is contrary to every other form of labelling. The reason is that vehicle manufacturers need to know what they can run which will not ruin teh EFI/engine management sensors. The 50 weight oils are excempt from the restriction because they are designated for old non efi engines. The BMW oil actually had 0.36% additives. But an oil might not contain any additives at all and still be entitled to claim compliance with many grades. beware an oil that meets many grades. IF oil was petrol they could sell kerosene as 100 octane because it is less than 100 octane. This is counter to what you would expect. In other words chip oil meets all standards because it has less anti wear additives ( zinc/phosphorus/calcium) so meets teh standard. For an old technology engine you are often better served buying diesel engine oil than the stuff marketed for petrol engines.

Old bmw i cannot argue with what you say cos I really dont know and I aint any kind of oil scientist - just going off the stuff they the manufacturers tell you. I will stick to me castrol 20/50 sg oil in any case, Anyway if your at the scottish weekend in september upto applecross - be good to have a chat after many s cos I am sure it will all make sense then. Cheers Jake.

You are probably right to stick to castrol SG only 20/50. here in the eco friendly France, the best I can get these days is 20/50in SL Where do you buy it, i might try to get a can next time we vist the UK?

wont be coming to Scotland although I will be going to Germany in acouple of weeks for teh annual Diesel Bike meeting at Hamm
The one in westfallen.

Oil like petrol is getting worse and worse,,, while they figure out how to dilute it more and more with substitutes.

I can order the castrol through my local car shop but BMW service shops also stock and use it in place of the old BMW sg oil. So I would think any bm dealer should supply it as its now recommended by BMW for use in there bikes. Jake. I should be back in Germany in October some time but not set a plan yet.
Best wishes Jake.