Not The Typical Engine Oil Question

Let me start out by saying I don't want to start a war on what engine oil is best. I want to followup on a subject that was talked about a few times on the forum and refers to ZDDP in engine oils. From a 2017 thread it was related that only Castrol GTX motorcycle oil still had ZDDP additives. Does anyone know if ZDDP additives are as important today as they once seemed to be and if so, is Castrol GTX oil still the only oil with these additives? What I gathered from my reading was that the ZDDP additive was especially important with flat tappet camshafts and wear issues between the camshaft and valve shim. Is this still correct today? The thread was a few years old. Does anyone recommend a ZDDP oil additive anymore?

This also made me wonder why Kawasaki listed only multi-weight oils for use in their FSM. Does anyone recommend a straight weight oil? For some odd reason I seem to remember using a straight weight oil in my then new 1975 Z1-B, but that was a long time ago. I thought we ran straight 40 weight in spring and fall and straight 50 weight in summer. Thanks for any responses.
Rick H.

Many, many motor oils contain ZDDP. See www.sccoa.com/forums/showthread.php?1363...tion-***Good-read*** for partial list.

I would never even consider using single weight motor oil in a car or bike. Multi weight oil works well at any engine temperature but single weight oil does not. Your bike engine is cold when you first start it and gets hotter as it runs. Multi weight oil protects it throughout those temperatures, single weight does not. Ed

To protect the catalytic converter & reduce pollution most car engine oils nowadays have reduced amounts of phosphate/zinc
compounds (such as ZDDP). Motorcycle oils still have high levels of phospho-zinc anti-wear ingredients. Shell Rotella 15W-40 regular has ZDDP & the JASO-MA rating. I've never heard of a straight weight engine oil for a car or Japanese motorcycle.

Phosphorus-Zinc content chart: Mobil 1 Racing 4T 10W-40 motorcycle oil
In the FAQ section at the bottom, click the first question, then click the "more phosphorus/zinc" link in the answer for a downloadable chart showing how much phosphorus & zinc are contained in the various mobil engine oil products.

Straight weight is for Harley's ,

"There is approximate 1200 parts per million ZDDP in Rotella T 15W-40,
which is 50% higher than is allowed in Starburst motor oils (API
SN/GF-5). Thank you for your interest in Shell products.

en.wikipedia.org/wiki/Zinc_dithiophosphate
www.hagerty.com/media/archived/classic-oil/

bluej58 wrote: Straight weight is for Harley's ,

"There is approximate 1200 parts per million ZDDP in Rotella T 15W-40,
which is 50% higher than is allowed in Starburst motor oils (API
SN/GF-5). Thank you for your interest in Shell products.

en.wikipedia.org/wiki/Zinc_dithiophosphate
www.hagerty.com/media/archived/classic-oil/

Yep I am aware of the Harley oils we ran back in the day. H-D 105. Pretty much all straight weight stuff. As I remember it, years ago there was some question if multi-weight oils actually worked as advertised. Was a 10W40, 20W40 or whatever really a bottom number when cold and a top number when hot. A lot of people ran straight weight oils in their cars and would change them out based on time of year. I also put a lot of credence of the sheer factor of various oils after comparing them in my BMW's with shared trans and engine oil systems. With new engine oil the transmissions in my BMW's will shift really smooth, but after about 2500 miles the transmission becomes notchy when shifting. I have exceeded BMW's engine oil weight recommendations for several years and have noticed the transmission shifts smoother for a longer period of time. Never noticed any excessive engine wear either. So after reading a plethora of threads on the subject it perked my interest.
Rick H.

Castrol GTX motor oil in 10w / 40 or 20w / 50 used to be the hot ticket to use when our bikes were new. Long ago Castrol reformulated
there oil for modern cars and it is no longer any good for our bikes.
I use Shell Rotella only these days .
OH , And Harleys no longer use straight weight oils.
Dave

I remember folks using straight weight in these bikes mostly because of oil leaks and hot summers.
STP was big then too.
ZDDP screws with the catalytic converters in modern machines but it is necessary protection for our type of lifters and cams.
The bike loves fresh oil and always runs cooler and quieter after a change.
15w40 diesel oil works for us, we get it on sale in big jugs and it is pretty cheap compared to racing oil

From what I've read over the years, ZDDP is bad for catalytic converters. Okay, then why are motorcycle oils permitted, oils that have a lot of ZDDP for their engines' transmissions? Don't most of modern motorcycles, at least the street ones, have catalytic converters?

Yes ZDDP is not good for catalytic converters, so if your bike or car has that type of exhaust don't use oil with a high level of ZDDP. Fortunately, no KZ model came with a catalytic converter, so for the KZRIDER it's not a problem. Ed

Your Z1B would have said on the filler cap what weight oil to use. Nowadays I use Kawasaki 10-40 in my engines...all of them are Kawasaki. The important thing for vintage bikes is the Jaso certification.

www.jalos.or.jp/onfile/pdf/4T_EV_LIST.pdf

All car and bike oils have ZDDP in them. Some more than others. Yes, catalyst damage is the reason ZDDP has been reduced, and that includes bike engine oils. The good news is that oil makers have learned to develop oils that resist engine wear using different additives. Shell Rotella is diesel engine oil and has a little more ZDDP than auto oils but it's been reduced as well. Frankly, I'm not sure how much it matters these days. Just change your oil and all will be well. Oh, and multigrade oils are designed so they flow better than straight weight when cold so they flow easier on cold starts and help protect the engine better because of it.

BohicaBob wrote: From what I've read over the years, ZDDP is bad for catalytic converters. Okay, then why are motorcycle oils permitted, oils that have a lot of ZDDP for their engines' transmissions? Don't most of modern motorcycles, at least the street ones, have catalytic converters?

I would think the new oils somehow satisfy the JASO-MA2 requirement while not having the same amount of ZDDP levels. Not sure. Or they are betting on bikes being less mileage, and therefore less of a concern of burning oil? Interesting to say the least.

I think only the more expensive models have cats. My Versys doesn't appear to have one unless it is built into the muffler. It does have an 02 sensor though.