Which is more important for low wear HTHS or ZDDP?

[Building3]

I'd like some wisdom as to the importance of these two factors in engine wear. Are these the two most important for wear considerations when looking at oil specifications?

 

[Overfill]

They are two important factors, but one doesn't replace the other, mainly because they act in two different wear-inducing scenarios/environments/events. Because of this, they have different priority in different locations in motors. At hot operating temps, I would agree that these are the two most important factors though, yes. If you were to look at it more granularly, I would say the next step is asking how these are going to change, given their environment, over the course of their use.

Generally, however, I would advise caution: hydraulic variable valve timing and lift systems may be an indirect limit to how high a HTHS oil you choose. If the OEM advises 30weight at 70 degree ambient, I would say that there will be potentially bad interaction with the VVTi/L system if you put in a 50 weight (50 weights are generally higher in HTHS than 30 weights) at 70 degree ambient temp.

Both of these, however, don't take into account wear that is unique to low operating temperatures. Unfortunately, I don't have something objective to look at beyond a KV40 viscosity. Maybe someone can answer that too. This importance would mainly be driven by how much the motor would be used at low operating temps (i.e. city driving)

 

[ka9mnx]

Great question! Thanks...

Basically HTHS benefits are in protecting rod and main bearings and to some extent piston rings. ZDDP is there to protect sliding surfaces like cam lifters, rocker arms and piston rings.

 

[Triple_Se7en]

Originally Posted By: Building3
I'd like some wisdom as to the importance of these two factors in engine wear. Are these the two most important for wear considerations when looking at oil specifications?


Don't be like me and take your badly rusted, purrs like a kitten, 18 year-old vehicle to the junkyard with low-wear and a clear dipstick.

I've done it twice already. Use any name brand oil and change it when needed. No need to look beyond simple and make things complicated. Rust in Michigan will ruin your many decades of vehicle ownership, tooling around 15-18K per year in salt-haven Michigan.

 

[Cujet]

ZDDP has no substitute, despite the claims.

ZDDP is good for more than just cams too. It reduces ring and cylinder wear. Engines that require oil with no ZDDP have some well known issues...

And, here is one method of dealing with the missing ZDDP:

 

[Building3]

Thank you for your detailed response. It was helpful. These engines are not anything exotic or new tech with VVT, etc. These are older but low mileage I6, I4, small V8 that only get driven in nice weather, so no below freezing temperatures. The only slat they would receive is if I spilled the salt package from my McDonald's drive through order. I want an oil that will protect the bearings after sitting for a month or two, and also an oil that will protect on short drives, but also highway driving at 90+ degrees in the summer.

 

[Kamele0N]

Rotella T6 in 5w40

And "dinitrol" cure for the rust...

 

[BrocLuno]

What engine?

 

[wemay]

Is Molybdenum a decent substitute for ZDDP?

 

[Garak]

Moly will work as an AW additive at higher levels than what you see in most motor oils. I'm thinking more around Red Line type levels, if I recall correctly.

 

[wemay]

Thanks Garak

 

[Building3]

Cujet: That is exactly what I do not want to happen!Mighty scary! Thanks for the photo. So if ZDDP and HTHS are key to low engine wear it sounds like, for example, since I found these numbers on their website, that these Mobil 1 oils would be good choices: 15w-50: HTHS 4.5 Zinc 1300 Phosphorous 1200; 5w-50: 4.4 1100 1000; 5w-40: 3.8 1300 1100

 

[FCD]

Originally Posted By: wemay
Is Molybdenum a decent substitute for ZDDP?

If that implies 0 Zddp, then no.

 

[BrocLuno]

Different chemistries, different reactions ...

 

[JAG]

There have been a very large number of studies on ZDDP and MoDTC. Sometimes the results can be contradictory but that is because the performance depends on the contact materials (Fe, Al, DLC, etc), temperatures, contact pressures, base oil(s) the compounds are in, as well as what other additives are also present. Seeing many studies, I concluded that I would not want to generally count on MoDTC doing a good job of wear prevention with ZDDP also being present in a sufficient concentration. They usually show a strong synergy when together in terms of wear prevention and the MoDTC typically reduces the coefficient of friction as well. Here is some general information:
https://books.google.com/books?id=DBR75H...ear&f=false

HTHS viscosity is for achieving hydrodynamic lubrication. Antiwear additives are for when that is not possible.