Oil viscosity and spec high zinc?

[Kapiti kiwi]

Hi guys I realise this may have been done to death but do we need a high zinc oil?

It appears from google that 5/40-20/50 is appropriate seems like a massive range 

[Kapiti kiwi]

Found a thread by Wambiker read through that seems most people use thicker oils 

I might go hunting for a 15/50 high zinc as we are heading to summer here 

[audiomick]

In the German forum that I am active in, someone provided a notice from Moto Guzzi about oil viscosities. Here is the text:

Quote

SERIE 750 (Breva und Nevada):

Motoröl: RACING 4T 10W-60 als Alternative 15W-50
Antriebsöl: ROTRA TRUCK GEAR 85 W -140, GL-4+/GL-5
Getriebeöl: ROTRA MP/S 80 W -90, GL-5


SERIE 850-1100-1200 (Breva, Griso und Norge):

Motoröl: RACING 4T 10W-60 Bei diesem Motor wird der Einsatz dieser Ölsorte eingehend empfohlen, da sie auch unter hohen Motortemperaturen optimale Druckwerte gewährleistet.
Antriebsöl: ROTRA MP 80 W -90, GL-5
Getriebeöl: ROTRA MP/S 85 W -90, GL-5


SERIE 1100 California - mechanische Ventilstössel

Motoröl: RACING 4T 10W-60 als Alternative 20W-50
Antriebsöl: ROTRA MP 80 W -90, GL-5
Getriebeöl: ROTRA MP 80 W -90, GL-5


SERIE 1100 California - hydraulische Ventilstössel

Motoröl: RACING 4T 5W-40 Für den korrekten Betrieb der hydraulischen Ventilstössel obligatorisch
Antriebsöl: ROTRA MP 80 W -90, GL-5
Getriebeöl: ROTRA MP 80 W -90, GL-5

I can't be buggerd translating the whole business right now, but if you look at the numbers, there's not much to it. "Antriebsöl" means "oil in the final drive", and "Getriebsöl" means "gearbox oil". "Motoröl" is, obviously, the motor.

The last entry, 1100 California, refers to a brief period in which California models had hydraulic lifters. Didn't work well, and didn't last long. "hydraulische Ventilsössel" is them, and "mechanische Ventilstössel" is the "rest of the world", i.e. purely mechanical, nothing hydraulich.

Whatever, as can be deduced from the text, at that point in time Moto Guzzi was recommending 10W60 for everything, except for the "exotic" Californias with the hydraulic tappets. 

I've decided, on the strength of that, to put 10W60 full-synthetic in all three of my Guzzis (1982 V35 Imola, 2003 Breva 750 i.e., 2002 V11 Le Mans) and they all seem to be satisfied with that. 

 

As far as the zinc goes, I've seen a lot of oil freds. In 10 replies you usually can expect at least 15 opions, but I can't remember anyone getting uptight about zinc content. 

 

To close up, if I remember correctly, @pete roper once wrote here "Yes, the motor needs oil. Put some in it." 

Edited Wednesday at 02:29 AM by audiomick

[Lucky Phil]

1 hour ago, Kapiti kiwi said:

Found a thread by Wambiker read through that seems most people use thicker oils 

I might go hunting for a 15/50 high zinc as we are heading to summer here 

Here's some key points about engine oil.

Always use a "full synthetic" oil.

The lower the "W" number the better. People that say a "0" weight oil is too thin don't know shit about oil.

Try to keep the viscosity spread to 30 units or less if possible.

Change it regularly

Don't allow your engine to do short runs that don't let the engine oil spend some decent time at operating temp.

Zink in a flat tappet engine? 900PPM to 1400 PPM is where you need to be. Too much is not good as is too little.

Phil

[Weegie]

Of course I agree with Phil

Not much to add on the Sport 1100 and the LM 1000 2 v/v bikes I run 15W/50 oil pressure is stable, even when the bikes get pretty toasty. The Sporti can easily reach 120C (around 250F) sump temp in traffic. When it starts to exceed that the bike quickly becomes unrideable, so oil pressure is academic. In clear air Sporti oil temp is around 80C (176F) although will rise quickly to 100C (212F)

The C kit HiCam is a different kettle of fish altogether, run a 10/60 in it, in clear air around 100C (212F), in town I've seen 140C, again totally unrideable by then. Still got idle pressure but dammed little.

Of course all the oils are group 4 full synth (so I've been told)

Purely anectodal but the only bike I've needed a 10/60 on is the C kit HiCam and that's because of the C kit cams.

Earlier HiCams (Daytona and Centauro) without the crazy cams aren't subject to the same heating issues.

No C kit cams went into US bikes.

[Pressureangle]

Here in the US when I have to use a non-preferred oil, for a change on the road, the simplest rule is to avoid any  SAE EPA rated oil. The tree huggers have taken pretty much everything out of the oil that doesn't burn in order to keep the catalytic converters active as long as possible. "Classic Car" oils, "Offroad competition", Outboard/marine 4 stroke oils and most OEM motorcycle oils still have good additive packages. 
I'm using 15w60 Klotz simply because it tops the charts in protection and I'm in S. Florida/Georgia and never have to worry about starting the engine below 40*F. 

The most important reason to use a full synthetic oil is that it stays alive in the valve guides. Natural oils coke up and wear the guides. This is critical in air-cooled engines. H-D had a huge problem with it in the early '70s, so bad the valves would actually sieze in the guides and get bent or bend pushrods. 

 

[gstallons]

On 9/16/2025 at 8:47 PM, Kapiti kiwi said:

Hi guys I realise this may have been done to death but do we need a high zinc oil?

It appears from google that 5/40-20/50 is appropriate seems like a massive range 

Zinc is considered to be an anti-wear agent. IDK why it has been weaned from oil but it has.

[Lucky Phil]

3 hours ago, gstallons said:

Zinc is considered to be an anti-wear agent. IDK why it has been weaned from oil but it has.

Because it's bad for catalytic converters. 

Phil

[PJPR01]

On 9/16/2025 at 10:44 PM, Lucky Phil said:

Here's some key points about engine oil.

Always use a "full synthetic" oil.

The lower the "W" number the better. People that say a "0" weight oil is too thin don't know shit about oil.

Try to keep the viscosity spread to 30 units or less if possible.

Change it regularly

Don't allow your engine to do short runs that don't let the engine oil spend some decent time at operating temp.

Zink in a flat tappet engine? 900PPM to 1400 PPM is where you need to be. Too much is not good as is too little.

Phil

Intriguing:  10W-60 full synthetic is the recommended oil for the Norge and Griso...are you suggesting that be 0W-30, 10W-40 or 20W-50 instead? 

[GuzziMoto]

1 hour ago, PJPR01 said:

Intriguing:  10W-60 full synthetic is the recommended oil for the Norge and Griso...are you suggesting that be 0W-30, 10W-40 or 20W-50 instead? 

That would be more to my liking. A wider difference between the two numbers means the oil relies more heavily on viscosity modifiers. Viscosity modifiers are complex molecules that coil up when cold and uncoil when they get hot. They are prone to shear, to being cut up, in use. As they get cut up they stop doing what they do. In essence, an oil with a larger gap between the two numbers will breakdown quicker. When you see an oil like 10w-60, it is a 10 weight oil with viscosity modifiers to give it the performance of a 60 weight oil when hot. But those viscosity modifiers that give it the 60 weight when hot aren't as stable and long lasting as the rest of the oil is. So as it gets older under use it gets thinner and thinner when hot. It takes more viscosity modifiers to make a 10w-60 oil then it does a 20w-50 oil.

That said, you can't go wrong using the oil they recommend. I don't agree with their recommendation, but it is their recommendation.

Edited Thursday at 03:13 PM by GuzziMoto

[Pressureangle]

9 minutes ago, GuzziMoto said:

That would be more to my liking. A wider difference between the two numbers means the oil relies more heavily on viscosity modifiers. Viscosity modifiers are complex molecules that coil up when cold and uncoil when they get hot. They are prone to shear, to being cut up, in use. As they get cut up they stop doing what they do. In essence, an oil with a larger gap between the two numbers will breakdown quicker. When you see an oil like 10w-60, it is a 10 weight oil with viscosity modifiers to give it the performance of a 60 weight oil when hot. But those viscosity modifiers that give it the 60 weight when hot aren't as stable and long lasting as the rest of the oil is. So as it gets older under use it gets thinner and thinner when hot. It takes more viscosity modifiers to make a 10w-60 oil then it does a 20w-50 oil.

That said, you can't go wrong using the oil they recommend. I don't agree with their recommendation, but it is their recommendation.

I had a customer back in the early 90s who was head of lubrication engineering at Ashland oil. We had just started racing 883s, so of course discussed thoroughly. He said, "All oils are equal for the first 5 minutes". The extended point was that oil breakdown is more relevant to your motor than what you start with. I could write a dissertation, but here are the high points;
Low viscosity oil is better for cold starts and tight clearances. Not prone to cavitation when cold. Throws off the crank more easily to lubricate cylinder walls better. 
High viscosity is better for high temps- because it's thinner at high temp than low viscosity at low temps. Counterintuitive, but often true. 
Low viscosity oils at high temperatures can burn and scuff off more easily- a situation that has little concern in watercooled engines but hugely important in air cooled engines. 
So while straight-weight oil is what usually finds it's way into strictly racing engines, it's because their operating conditions are stable. 
It was true 20-30 years ago that wider W ratings meant the oil broke down more quickly; still true, but not as quickly, and not as completely as before today's supreme quality synthetics. So viscosity breakdown (which usually means the oil thickens at low temps, rather than thins at high) happens well beyond reasonable change intervals. Since I'm in a year-round warm climate, and I rarely ride less than 100 miles at a crack, I use 15w50 Shell Rotella T6 diesel oil as my go-to if I can't source my preferred Klotz V-Twin 15w60. Rotella being a diesel oil still has anti-scuff additives that are gone from gas engine oils, but the detergent package means I change it at 5k miles where the Klotz looks good for 10k. Also, Rotella is half the price of Klotz. 

At the end of every oil thread, lies the fact that most engines simply don't much care what you put in them if you change it frequently enough. 

[GuzziMoto]

Oil breaks down in two directions as it gets used. As the viscosity modifiers breakdown the oil gets thinner when hot. This generally doesn't affect the oil when cold, the cold viscosity doesn't really change as the viscosity modifiers breakdown. The second is as by-products of combustion collect in the oil it tends to get thicker when cold. This has less impact on the oil when hot, mainly affecting cold flow. A third aspect of oil as it is used is that the additives get used up, reducing the protection the additives bring to the party. Things like zinc do what they do in oil by being used up. So whatever amount of zinc an oil starts with, as it is used there will be, over time and use, less zinc.

I do agree that the Guzzi V twin is not overly sensitive to oil, especially the 2 valve per cylinder engines. Some of us no doubt put more miles on their motorcycles then I do nowadays, sadly for me. I usually change my motorcycle oil due to age before mileage. Presently I only have one motorcycle that I change the oil based on mileage and not age, and even that one is likely to be changed based on age this time as I just haven't had time to ride enough this year.

As always, an oil thread can be a slippery slope. But I am bored.

[PJPR01]

What is the life expectancy of the viscosity modifiers under normal, not arduous use?  Does one really need to be concerned about that when using 10W-60...I've never given it a thought on my 2008 Norge bought new, with almost 60K miles and still not consuming a drop of oil between oil changes.

Edited Thursday at 07:59 PM by PJPR01

[Lucky Phil]

8 hours ago, PJPR01 said:

Intriguing:  10W-60 full synthetic is the recommended oil for the Norge and Griso...are you suggesting that be 0W-30, 10W-40 or 20W-50 instead? 

Probably the same logic that Guzzi built engines in those days with flywheels the weight of a V8 car engine or used linked brakes or produced an engine with the easiest valves in the world to adjust and gave it hydraulic lifters or used DLC coated lifters that shat themselves because it was the totally wrong tech for the application. You know, that logic. 

Phil

Edited Thursday at 09:54 PM by Lucky Phil

[audiomick]

So, thanks for the last couple of posts. As I wrote further up, I have decided on the strength of a Guzzi bulletin from some time ago to put 10W60 in all three of mine. The last couple of posts have further confirmed this decision. Why? I don't do an awful lot of miles, I do ride all year. That means also at temperatures around 0°C plus/minus a couple. I do ride more short trips (to work and back) than I do trips out of town. But the trips out of town do happen. So I want a wide range to cover the short, cold trips and the longer trips where the motor gets hot. And I'm not about to start changing the oil twice a year to cover winter conditions differently to summer conditions.

So, a wide range oil. If I ever find a 0W60 I might give that a go too.

If anyone can see a fault in my logic, I'd be glad to read it, but the argumentation needs to be good. 

PS: that it is necessary to keep the oil-change interval well within bounds is clear. I've ordered a round tuit to that effect. 

Edited Thursday at 10:46 PM by audiomick