Why would I need higher then 30 grade synthetic?

[4evrnyt]

After reading the Oil 101 article I came away wondering; if synthetic oil doesn't change grade over time why would anyone need to use higher then 30 grade. If most engines require 10cs at operating temp and that can be achieved with 30 grade oil what benefit is there to running a higher grade synthetic oil then 30 grade?

Do manufacturers list the cs requirement of their engines?

Thanks for your help and time.

 

[UncleDave]

Never seen an auto manufacturer state CS requirements, but maybe I never looked hard enough.

Synthetic oil can absolutely shear out of grade.

Nissan VQ engines with multiple feet of chains and multiple sprockets are known shear engines.

I feel more comfortable towing 7500 lb in 105 degree heat 5K into a 7.5K OCI with 0w40 than 0w30 with my titan.

I had a bunch of blackstone testing done in 04 when I bought the truck and they showed it could easily shear a full 10 points of more down before the end of an OCI.

Diesel and high performance gas DI engines also shear oil down with the high pressure pumps.
They have to put between 20 and 30K PSI on a rail and that energy usually does from a cam lobe and that squeeze puts a lot of load on the oil.

UD

 

[CT8]

Oil 101 is more opinion than fact, don't consider yourself educated because you read oil 101.

 

[tig1]

My Ford 4.6 V8 had multiple feet of chains and they always performed well and no obvious shearing of the oil.

 

[Quattro Pete]

Originally Posted By: 4evrnyt
if synthetic oil doesn't change grade over time

It can certainly change viscosity and thus fall out of grade over time.

 

[bbhero]

Very well stated UncleDave. That's my main concern about my 3.5 VQ motor is all the chains it has. It is a great motor that sounds very good. But I sure can see it tearing oil viscosity down in a quick fashion.

UncleDave do you think a Dexos and HTO-06 approved oil would resist shear a bit more than just a regular full synthetic?

 

[aquariuscsm]

Motor oil 101 should be moved to the humor section. "Synthetic" is just a marketing term. It's oil,it comes from crude,therefore it will shear and sludge just like a "conventional" (MAYBE with the exception of an uber expensive ester based oil). Spend some time studying the uoa's here. Pay special attention to the tbn and viscosity numbers. My car sheared Royal Purple 20W50 down to a 10W40 in only 3200 miles.

 

[Shannow]

Originally Posted By: 4evrnyt
After reading the Oil 101 article I came away wondering; if synthetic oil doesn't change grade over time why would anyone need to use higher then 30 grade. If most engines require 10cs at operating temp and that can be achieved with 30 grade oil what benefit is there to running a higher grade synthetic oil then 30 grade?


I've repeatedly asked the author of 101 where he gets the understanding that engines are designed for 10Cst KV100, and hear chirping crickets every time, then some time later he'll point newbies back at it.

Manufacturers don't spec a KV100 directly, but they DO spec it indirectly by speccing different grades, the latter number of which has a range of KV100s.

More recently, focus has been on the viscosity characteristic that actually DOES most of the protection, and that's the HTHS...again, misconstrued in 101 by interchanging Cp and Cst.

Lots of manufacturers have set minimums on HTHS, and seeing as you have specifically mentioned "30s", a straigh mineral SAE30 dino will have an HTHS in the range of 3.5, and the multigrade synthetics can go from 2.9 (ILSAC economy grades) to 3.6+ (ACEA A3/B4, C3 type oils).

 

[UncleDave]

Originally Posted By: bbhero
Very well stated UncleDave. That's my main concern about my 3.5 VQ motor is all the chains it has. It is a great motor that sounds very good. But I sure can see it tearing oil viscosity down in a quick fashion.

UncleDave do you think a Dexos and HTO-06 approved oil would resist shear a bit more than just a regular full synthetic?


Couldn't say about dexos or HTO-06 rated oil being better.

I always ran mobil 1 0/5/10-30/40 I think these engines are just going to shear oil whatever you put in and that the only real way to deal with it is to keep the OCI reasonable.

I loved my g35 with the VQ35 - I traded it for the lexus rx400h when my second wife arrived with 2 teenagers from Canada.....

Couldn't speak to the Ford 4.6's characteristics as I never owned or studied UOA's from them.



UD

 

[BrocLuno]

Oil 101 is nout how to understand the issue. There is a whole lot more reading and study needed to understand the issue.

One salient factor is how hard will the engine be run? If it's flat to the floor for an hour at a time pulling a trailer over the Rockies, you'll need to step up your oil Why? Because you will adding so much heat that a 40 will be acting like a 30, or maybe even a 20 under high RPM, high load situations ...

If you are just commuting, no, you do not need to go above 30

 

[Shannow]

Reinforcing what BrocLuno is suggesting, here's some temperatures from a test engine in a paper.

At those sorts of speeds, the bearings are operating in the High Shear Regime, and clearly quite high temperatures...if you were operating the car predominently in either one of the rev ranges, you might elect to change your oil preferences

Another one, looked at differently, depending on RPM and bulk oil supply (sump) temperature. Number on the right is the oil supply temperature, and the left hand scale is the temperature that the big ends got to.

 

[bbhero]

I like these pictures and the graph Shannow. Quick question I have is this.... What about a rather short duration of high rpms?? Let's say like 6 seconds worth of high rpms. How much would that raise oil temps up too? And how long would it take for them to return back to normal afterwards given rpms being around say 2k??

 

[Shannow]

bbhero,
a short burst for example overtaking, the bulk oil is still at whatever steady state temperature it was to start with.

The big end bearing will start climbing immediately, but not reach it's peak for a minute or so.

 

[bbhero]

Ahh ok that makes sense. I am hypothesizing but the fact it takes a minute for the peak temp to be met I guess is that the energy applied takes awhile to fully "catch up" so to speak.

 

[Shannow]

Yep, the shear in the oil film is there immediately, but that heat has to heat up the surrounding bearing materials before it attains equilibrium.

 

[UltrafanUK]

Originally Posted By: 4evrnyt
After reading the Oil 101 article I came away wondering; if synthetic oil doesn't change grade over time why would anyone need to use higher then 30 grade. If most engines require 10cs at operating temp and that can be achieved with 30 grade oil what benefit is there to running a higher grade synthetic oil then 30 grade?

Do manufacturers list the cs requirement of their engines?

Thanks for your help and time.


Although most petrol engines are listed for 30 grades (Or even 20 in the US and Japan), many diesels and some race engines list 40 grades.
It's also worth thinking about using a 40 if your engine contaminates its oil with fuel or has suffered a lot of wear and has a high oil consumption.
It's also worth thinking about thicker grades if you are using your car for towing in a hot climate.

 

[Merkava_4]

Spelling 101 says you got then/than mixed up.

 

[Donald]

Originally Posted By: aquariuscsm
Motor oil 101 should be moved to the humor section. "Synthetic" is just a marketing term. It's oil,it comes from crude,therefore it will shear and sludge just like a "conventional" (MAYBE with the exception of an uber expensive ester based oil). Spend some time studying the uoa's here. Pay special attention to the tbn and viscosity numbers. My car sheared Royal Purple 20W50 down to a 10W40 in only 3200 miles.


The condition of the basestock is indicated by viscosity and if a Polaris UOA, oxidation. TBN is more the condition of the additive package.

 

[FCD]

Motor oil 101 is a joke

 

[zeng]

Originally Posted By: BrocLuno
One salient factor is how hard will the engine be run?

+1
How hard the engine (or differentials,transmission gear components) is designed to run ..... forms the basis of my final selection of viscosity grade, with OEM recommendation being a reference.
The add pack loves it ..... the basestocks loves it..... and the wear components loves it!
Loss of FE ?? .........
ooh, I regain FE by upping tire pressures up to 10-30% higher than recommended ...... as long as the ride is comfortable.


Originally Posted By: Donald
The condition of the basestock is indicated by viscosity and if a Polaris UOA, oxidation. TBN is more the condition of the additive package.

+1