Conflicting info for Motor Oil

[Slade]

My owners manual says to use 4-stroke oil for my
79 850GS, but the manual i downloaded from Basscliff states to use 10-40 oil
(anyone know which one is wrong???)

[almarconi]

Do a search, there are tons of threads on motor oil.

10w40,15w40,5w40 are all good to use in your bike. Make sure that they don't say "energy conserving" on the label. I use Rotella 5w40 synthetic in my bike, no problems.

[koolaid_kid]

Ummm, all motor oil is for 4-strokes unless it is labeled for 2-strokes. The difference is the 2-stroke oil is combined with the intake mixture or injected into strategic points to lubricate the bearings and rings. 4-stroke oil is kept in the crankcase for the same functions.
10w40 et al is the weight or viscosity of the oil and is a rating from the manufacturer. The smaller the number the thinner the oil. The "w" on the 10w means the thickness when cold, the 40 means the thickness when hot. The most generic weight is 10w 40. It starts out fairly thin, then gets thicker when it heats up, which is what you want.
This issue is much, much more complicated than can be explained in a thread like this, but these are the basics.

[Agemax]

Ummm, all motor oil is for 4-strokes unless it is labeled for 2-strokes. The difference is the 2-stroke oil is combined with the intake mixture or injected into strategic points to lubricate the bearings and rings. 4-stroke oil is kept in the crankcase for the same functions.
10w40 et al is the weight or viscosity of the oil and is a rating from the manufacturer. The smaller the number the thinner the oil. The "w" on the 10w means the thickness when cold, the 40 means the thickness when hot. The most generic weight is 10w 40. It starts out fairly thin, then gets thicker when it heats up, which is what you want.
This issue is much, much more complicated than can be explained in a thread like this, but these are the basics.

that is not the case, it actually gets thinner as it warms up. the last number denotes how thin it gets at 100centigrade, so a 10/30 will be thinner at that temperature than a 10/40,which will be thinner than a 10/50, and so on

[bwringer]

Also keep in mind that the manual was written 30 years ago. Oil is a lot better nowadays.

Use just about any oil somewhere in the correct viscosity range, change it every 2,000 miles, and worry about something else. I don't think there's ever been a GS engine failure attributable to oil quality.


I agree with the following:

10w40,15w40,5w40 are all good to use in your bike. Make sure that they don't say "energy conserving" on the label. I use Rotella 5w40 synthetic in my bike, no problems.

If you're not sure, go with a name brand 15W-40 intended for diesel engines. It comes in handy gallon containers for $10-$15 each. The 5W-40 synthetic is around $20/gallon. The oil for diesels contains extra detergents and dispersants that also make it work very well in air-cooled engines.

One thing that's certain is that you do NOT need ultra-expensive motorcycle-specific oil.

[Nessism]

Diesel oil is good stuff. It has more high pressure additives than car oil which is good for motorcycles since our engines share the oil with the transmission and the gears chew up the oil pretty good.

[BassCliff]

Hi,

A few words from your "mega-welcome":
-----
A Few Words About Oil

I'll tell you what I use and why. I use Rotella-T Heavy Duty 15w40 oil. It is actually diesel engine oil and contains more anti-wear additives, phosphorous and zinc, that these older high-revving engines love. At about $12 a gallon from Wal-Mart, it's less than half the price of many motorcycle-specific oils, and is the best "bang for your buck" value. The synthetic Rotella-T is just fine too, it won't hurt your clutch. If you like, continue reading the links below for everything you ever wanted to know about oil but were afraid to ask.

Here's a great article on motorcycle-specific oil in general.

Here a 2nd great article, also on motorcycle-specific oil.

Sport Rider Magazine ran a feature awhile back on motorcycle oils as well, and included some testing with detailed results provided. Well worth the read!
Sport Rider "Oil's Well That Ends Well" Part 1
Sport Rider "Oil's Well That Ends Well" Part 2

Richard Wildman (of Richard's Corvair) explains in layman's terms all about grades, viscosity, shear, additives, specs, etc.
Richard's Corvair - Selection of the Right Motor Oil for the Corvair and Other Engines

And, of course, Bob the Oil Guy is a fountain of information.
-------

Thank you for your indulgence,

BassCliff

[ddaniels]

+2 on the Rotella. I've used it many many times with no problems. Cheap too.

[850 Combat]

I had been using Castrol GTX 20-50 in my English bikes since the 70's. On some Nortons, the manual actually says to use Castrol. This practice was caried it over to the little fleet of GS bikes when I bought them 4 or 5 years ago for tours with my brothers. There was a bit of clutch slip noted on a couple of them when shifting into higher gears at high RPM and large throttle openings. I figured it was just the age and mileage. After switching to Rotella, mainy for the zinc, I noticed that the clutch slip is reduced or gone.

Now I think that friction modifiers like molybdenum in the Castrol may have contributed to the clutch slip.

It might be worth noting that in an English bike, the engine, clutch, and transmission each have their own oil, all different.

[chuck hahn]

10-40 IS 4 stroke oil!! LMAO. I use the same as everyone else ROTTELLA T. Only i run 15-40 instead of 10-40

[hampshirehog]

It might be worth noting that in an English bike, the engine, clutch, and transmission each have their own oil, all different.

Mostly, but not all, and not just English bikes. Plus a lot of Royal Enfields for example, use grease in the transmission (and oil still leaks out of the gearbox.......).

Ummm, all motor oil is for 4-strokes unless it is labeled for 2-strokes. .

To confuse things a lot of 2 strokes use 'motor oil' eg 10W40 in the gearbox and for lubricating the main bearings if the oil seal is on the big end side of the bearing. And some 2 strokes, eg old eastern bloc stuff just specify 'oil' - presumably you're just meant to guess or use the stuff left over after cooking the chips

[koolaid_kid]

To further confuse, lawnmowers and such use non-detergent oil. Not so common now, but the basics are - detergent oil stirs up the contaminants and suspends them in the oil. Filters trap the contaminants. Engines with no filters (mowers, high pressure washers, etc.) use non-detergent oil. But still 4 stroke oil.

[koolaid_kid]

To confuse things a lot of 2 strokes use 'motor oil' eg 10W40 in the gearbox and for lubricating the main bearings if the oil seal is on the big end side of the bearing. And some 2 strokes, eg old eastern bloc stuff just specify 'oil' - presumably you're just meant to guess or use the stuff left over after cooking the chips

IIRC (it's been a while) my T200 and other 2 stroke street bikes did that. Oil for the gearbox, injection for the crank. However, because the gearbox was not affected by combustion pollution, the oil would go a lot longer.

[Slade]

Hmm

10-40 IS 4 stroke oil!! LMAO. I use the same as everyone else ROTTELLA T. Only i run 15-40 instead of 10-40

I thought it was also, but 3 different motorcycle shops here in Oregon told me that I needed to buy that said specifically "4-stroke-oil" which most oils do not say....Since I am new to the Motorcycle scene, the only stupid question is the one not asked IMHO!