Best Oil for Rover V8s ?
Discussion
Incorrigible said:
Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot
Another way certainly but they can't both be right
Why not? That makes sense to me - a single grade 20 oil would thin with temp in the normal way. A 50 grade oil would also thin but for every given temp would be thicker than the 20 oil. The multi-grade bit means at low temps it's a 20 and at higher temps it behaves like a 50.
The bit we need to know is, as you said earlier, how it changes over temp. We know 40degC and 100degC but what about in between?
Yes I see that, but what I meant by they both can't be right was ....
either it's an oil that has viscosity 40 at 10 degrees
or viscosity 40 when cold and 10 when hot
The 10 means one thing or the other
The herb infused ones cost a bit more, but they smell so much better when they're burning off you exhaust manifold
either it's an oil that has viscosity 40 at 10 degrees
or viscosity 40 when cold and 10 when hot
The 10 means one thing or the other
The herb infused ones cost a bit more, but they smell so much better when they're burning off you exhaust manifold
Incorrigible said:
... The '0' winter rating indicates it is a bit thin when cold, which is not so good, but also that it has a flatish viscosity~temperature curve , which is probably good.
Haven't you got that back to front
The oil gets thinner as it gets hotter reducing to 0 (not really 0 but damn thin in Mobil 1's case)
Yup, but I can see how you might have mistook my meaning, which, in a nutshell, was that 0w is thinner that 15w when cold. Bear in mind you don't really care about sapping the engine power or reducing the flow rate when your bearings are cold - what's the point of 0w, it's the 40 that matters to your power??
The viscosity reduces with temperature, as well as shear rate (there's also normal force, thixotropic effect, and viscoelastic effects - but let's not). What I meant was, because of the way that true viscosity corresponds to the numbers on SAE scales, '0w' is not much higher viscosity than '40'
, so that suggests that when you start a cold engine the oil might not be the grease you'd want it to be, but that at real 'hot' bearing temperatures ('40' being awarded at a fairly 1.0litre diesel-like 100°C), the true viscosity is still somewhere near to the '40' you're led to believe by the packet. What I'd really like to know is are there any TVR/Rover V8's that've done >100k miles on original unmolested engine, and what oil they used? I think I'll post a new thread!
rat said:
What I'd really like to know is are there any TVR/Rover V8's that've done >100k miles on original unmolested engine, and what oil they used? I think I'll post a new thread!
There are some that are out there that have used Mobil 1... There are some that have used mineral oil that had cams die in about 10k miles... there are engines that have done 100k miles on round cams when their owner's didn't notice it as the loss of power was gradual... As i described in the bible oil essay, I found examples that effectively knocked holes in every "this oil is best" argument put forward. Oil is a religious dogma. best advice is use a good one, change it regularly and don't rev the engine when cold. Won't protect you against cam failure as there appears to be other reasons/factors involved but the alternative is waiting in bed for the knock of the oil police to take you away...
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