Motor Oil

[dakinebusa]

Them Harley Davidson thingies are roller bearing motors like old BMWs and have entirely different oiling needs from journal bearing high speed motors.
The usual mix of bull semen and bear snot that works just fine in my ole shubblehead would sieze a Ducati motor...
I use gold cap Mobil 1 10-40 car oil in all my bikes and v8s and it delivers all the benefits expected of synthetic oil.
The Motorhead (Bonneville record holder) runs Mobil 1 car oil in his 500+ hp turbo Hayabusas without clutch slip or other problems.
Bike specific oil is great marketing but frequent oil changes are better ;D

Originally Posted by Georgecls

Should have been more exacting in saying a 15W-50 ot 20W-50 but both oils ARE true 50 weight oils at engine operating temperatures. Slipped into engineering talk of operational viscosities...
George Morrison, STLE CLS

George, you say that a 50 weight oil is 50 weight at engine operating temperatures, but I thought a 50 weight oil was 50 weight at 100°C ?

[dakinebusa]

http://www.bobistheoilguy.com/visc.html

[ducpainter]

Originally Posted by dakinebusa

http://www.bobistheoilguy.com/visc.html

So is that chart saying that a 20W-50 engine oil is 20weight at ambient or 50weight at 1000C, or both?

[Georgecls]

In API engine oil viscosity designation, the "W" is the "winter" rating for the oil. This system was originally designed for mineral based oils, when "multi-viscosity" came into being. Mineral oils are very sensitive to temperature changes: when cooled they thicken, when heated they thin. The old single grade oils were lilke molasis at 0 degrees F. Magic of chemistry came along. Multi vis. How we make a 20W-50 mineral based oil is to start out with 20,000 gallons of 20W oil, then throw in viscosity improvers which are essentially plastic coil springs (plastomers) which expand with temperature, shink with cold. Thus when we heat this 20W oil up to operating temperature, the plastic coil springs expand, giving the 20W oil the apparent viscosity of a 50W oil. When the oil cools down, the coil springs shrink and we are back to our 20W oil we started with.. Which flows like a 20W oil at 0 degrees F. Because it IS a 20W oil..
Now to full synthetics. All the above does NOT apply. To make a 20W-50 API rated oil, we start out with a 50W base stock (essentially) and do nothing. When full synthetics are cooled, they do not thicken as mineral base oils do. Same when heated; they retain their viscosity and do not thin. Which is one of the major positives for synthetic based lubes: they provide the film thickness at higher temps yet allow easy start-up. No VI improvers needed with this oil, although in the real world VI improvers are used minimally to allow large scale production and insurance of exceeding API requirements.. But even in full synthetics, when the range gets to a 0W-50 or so, there is a slug of VI improvers in that mix.. The downside of VI improvers are that they shear, are subject to load shock, etc. NOT as good as a full synthetic molecule...
So, the old wives tail about synthetic oil being thinner is completely innacurate. Full synthetic engine oils are thicker both in base stocks and operationally..
Hope I have clarified. If not, keep the questions coming.
Thank you,
George Morrison, STLE CLS

[22080]

So, George, when Ducati put sticker on my engine saying 20W - 50 they where wrong?

[Georgecls]

No, for those with a 20W-50 designation by Ducati, by all means run Mfg recommendation.. Mine says 10W-40 and for those whose manual says 10W-40....... (however, methinks this 20W-50 recent recommendation changge is related to Shell's Ducati racing sponsorship and Shell's not making a 10W-40 full synthetic motorcycle oil... Woops, lets change that manual to read 20W-50 don't want to be recommending an oil our sponsor doesn't make!)
Like with Ford and Honda discovering the glitch in CAFE fuel mileage that enabled huge paper gains in corporate cafe by merely switching from a 5W-30 to a 5W-20 engine oil. Millions of dollars of engineering could not equal what the stroke of a pen achieved...

[BCT_Dark]

So the book basically recommends virtually all grade of oil for use in their motors.
Are you saying one 'grade' is better than another for use in the Ducati aircooled twins?

Cause the popular ones these days seem to be 10w-40 for water cooled and 20w50 for the aircooled, which I assume to be attributed to the fact that water cooled motors are built with tighter tolerances due to their ability to 'regulate' heat better, and aircooled motors built 'looser' to accomidate the massive fluctuations in heat within the motor.

???

[ducpainter]

So to put it very simply a 20W-50 full synthetic flows like a 20w mineral at ambient with little or no modification to the base stock?

Originally Posted by Georgecls

When full synthetics are cooled, they do not thicken as mineral base oils do.* Same when heated; they retain their viscosity and do not thin.*George Morrison, STLE CLS

That doesn't make sense to me George. You're saying the viscosity is the same at 180°C as it is at 20°C?