Synthetic Oil or not?

I have zero doubt synthetic oils have superior lubrication and flow characteristics. I've repeatedly heard they are not good for vintage wet clutches. I haven't tempted fate with my 70's and 80's motorcycles. Clean Dino, JASO rated with an ounce of ZDDP will remain in mine until I can point to an oil related failure.

Z!Driver: does your C14 have roller rockers? What oil does the owner's manual prescribe? (since we are sittin' on the couch with snow on the ground)

We ran Mobil-1 15w-50 in our '93 CB750 Nighthawks for over 50,000 mi. with zero problems. NAPA had a sale on their synthetic 15w-50 (Valvoline) not long ago, so we tried some. Shifting is noticeably more notchy, and neutral is more difficult to find using it. Back to Mobil-1 15w-50 when the NAPA is gone.

Kawasaki 20w-50 mineral oil is all our Z-1's have run for the past 20 yrs. or so.


Good Ridin'
slmjim & Z1BEBE

Years ago I used dino auto oils in my Zs. Then when the federales forced the oil companies to reduce the zinc and phoshorous content in auto oils, I switched to M/C oils which cost quite a bit more. Eventually I switched to cost-effective Shell Rotella 15W-40 for a number of years until I learned from Shell that it too was being forced to reduce its zinc and phosphorous content in Rotella. It was then that I switched to AMSOIL MC 20W-50 oils, then to AMSMOIL MC 10W-40 oil because this oil runs about 15 degrees F cooler in my Zs. Never had any clutch issues with AMSOIL MC oils.

Nessism wrote: Being devil's advocate here but there are quite a lot of cars sold these days with synthetic oil from the factory. Some people say machining tolerances are better today which may be true, but a hone is a hone and rings haven't changed all that much. That said, I run mineral oil in my 750 after rebuild but will switch over to synthetic and/or semi synthetic at some point because that's what I've got in the cabinet.

Also, the automotive grade 20w-50 M1 oil has a lot of fans in the bike community. 20W-50 oils don't have the stuff in them to wreck a wet clutch; friction modifiers that are labeled "energy conserving" are the ones to be most concerned about and those are only in the lightweight oils.

Again, I'm playing devil's advocate here, not strictly recommending. Just making a point that there are counters to many of the arguments that people make regarding oils.

Ed, apologies, I missed your comment about friction modifiers in synthetics that create havoc on wet clutch systems. Guess I was being redumbnant.

This might have been posted already, but has some good information for the original poster. Use oil marked JASO MA for wet clutches.

www.oilspecifications.org/

Then this:

www.whitedogbikes.com/whitedogblog/choos...o-and-jaso-ma2-mean/

Fire Hawk wrote: Z!Driver: does your C14 have roller rockers? What oil does the owner's manual prescribe? (since we are sittin' on the couch with snow on the ground)

The C14 has shims under buckets with the motor being really a detuned ZX14 motor and water cooled. Shims changes are a pita with the cams needing to be removed to get under the bucket. Owners manual doesn't suggest type of oil, only the weight depending on outside temp. Being cold and snowy out side the Z1 waits for a new front tire, fork seals and dyno cover wire seal.

Personally, I think the two most important criteria are---
JASO-MA certification
Appropriate viscosity (weight)

These old bikes are particularly hard on engine oil. It not only has to provide lubrication for cams, followers, crank and rod bearings, and cylinder walls, it also aids in cooling and has to withstand severe shearing forces in the transmission, and has to cool the clutch. In the mean time, it also has to suspend and wash away particulates from engine, clutch and transmission wear.
It has to do all these things under a wide variety of temperatures and while constantly being attacked by combustion blowby, heat, and humidity.

Kawasaki established recommendations based on performance requirements and what was available in the marketplace, thirty-five to fourth-five years ago. Much has changed since then. I am willing to bet that any national brand non-synthetic oil of today will out perform the best of yesteryear.

Fully synthetic oils are better at resisting viscosity breakdown than non-synthetic oils, and this certainly seems to be a good thing for us. I think the more important question is how much protection is enough? To me, the obvious answer is, it depends. A motorcycle that is raced in the heat of summer, or that spends many hours touring with a full load of people and gear will destroy oil much faster than one that is ridden lightly in moderate temperatures.

Since synthetics break down more slowly, the mileage between changes can be dramatically extended. Clearly, a high quality filter is necessary for this, but shouldn't we all be using one anyway? :whistle:

Is using synthetic oil and changing it on the factory schedule a waste of money? I do not know, but I suspect it is.

ymmv