Consensus is less VII's the better. I don't think anyone would dispute that. Are there any reasons where VII's are ideal even in high performance applications?
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Read our primer articles on High Mileage Oil, Synthetic Oil and Kinematic Viscosity
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Buster, what is it thats bad about VII's?
quote:Originally posted by Buster:
Consensus is less VII's the better. I don't think anyone would dispute that. Are there any reasons where VII's are ideal even in high performance applications?
VII are best where there are big temperature variations. A daily driver might be exposed to -20F on up to 100F. You need a thin oil that will start cold, but still be thick enough to protect from heat. Racing has little temp variation and very start ups. Lots of high temp/pressure situations though. Not a good place for VII, IMHO.
quote:what is it thats bad about VII's?
They don't lube as well as oil, they break down which thins the oil, maybe a contributing factor to sluge/sticky rings, etc....
The answer to most peoples questions about which oil or what's better is how the oil is used. VII's are great to meet the viscosity requirements at lower cost than using premium base stocks. If you don't run your vehicle in extreme conditions and not looking for long extended OCI then VII's are a great thing. I think that most people who spend big dollars on certain brand synthetics are not getting the full benefits of that oil, either by to short of OCI or it's just not required to meet their driving styles or operating temperatures.
Just my 2 cents..
Just my 2 cents..
Very good post PetrochemUK. This is the type of technical information that I enjoy on this forum. I didn't realize that VIIs had changed.
This is the type of technical information that I enjoy on this forum. I didn't realize that VIIs had changed.quote:Originally posted by PetrochemUK:
Old VII used to have the problem of being 'torn apart' or decomposing in high pressure shear-stresses found around surface interfaces(leaving waxy, polymerised deposits), however this problem has been overcome by the design of a 3D type 'star' shaped polymer (similar in appearance and action to a tumble weed) which will tumble along the interfaces when exposed to shear stress, rather than decomposing.
That sounds like the Shellvis/Pennstar vi improver . It's been around over a decade now and is offered in at least three molecular weights , maybe more .
Elastohydrodynamic lubrication of base oil comes into play when pressures are extremely high in the engine bearing . Newer VM's are thought to throw some beneficial elastic properties to the lube reducing wear and friction in regards to elastic behavior .
When we see comments like ... wow , that ELF 10w-50 motorcycle oil must really shear alot -- well i am betting they know more about keeping bearings intact in a hi rpm engine than most Walmart shoppers
It goes beyond that actualy . Bearing shells and strengths of them these days are designed and used with viscosity in mind but yes , vm's seem to be of some benefit in racing engines from what i can tell .
Great post there MB. You need to come back to BITOG. 
