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It is only 0w when cold. When hot a 0w50 should have the same viscosity as a 20w50. That is an advantage when starting the car cold.
This is not exactly accurate. As the viscosity range extends, the warm oil viscosity is reduced. Frex; Castrol 0W-40 has a viscosity of 13.5cSt at 100C, where 5W-40 has a viscosity of 13.9cSt at the same temp. This is true for other vendors and is a function of the additive package and how it affects the base oil. Unfortunately, vendors don't rate their viscosity at low temps, but that's not important for warm oil viscosity.
I'm not sure how you can say that when most local auto parts stores no longer stock any oil suitable for a 928 in a warm climate.
My local auto parts stores only stock one 40wt, and that's 5w-40 Turbo Diesel Truck (which I do use in the Saab in winter)
About the only oil our local auto parts stores stock that I'd consider using is the VR1 and I am totally opposed to Valvoline in our cars after talking to an engineer that works there. Walmart on the other hand stocks the 15w-50 so it's a mute point.
When using the 20/50 weight oils, I always run the engine / oil up to temp before any High revs.
As not doing so can cause Cam Pitting, it can also be caused by corrosion due to excessive moisture in the oil (think short starts to move a cold car) and there are other factors that all add up.
Another good option is Brad Penn Racing 20w50 but it may not be readily available in all areas. I am lucky to have a distributor close by. It's the old Kendall GT1 oil and used widely in circle track and drag racing world, lots of zddp and phosphorus.
About the only oil our local auto parts stores stock that I'd consider using is the VR1 and I am totally opposed to Valvoline in our cars after talking to an engineer that works there.
Is that the engineer that was friends with Greg Nettles?
About the only oil our local auto parts stores stock that I'd consider using is the VR1 and I am totally opposed to Valvoline in our cars after talking to an engineer that works there. Walmart on the other hand stocks the 15w-50 so it's a mute point.
scot was using the valvoine, until we saw the oil pressure drop syndrom with it, similar , but not as bad as the mobil 1. We will never put that stuff in a car going to the track either!
And bottom line is most oils will work just fine......
true for street duty, ill agree
Originally Posted by Cosmo Kramer
The wider the range between the cold and hot viscosity ratings requires a lot more additives to make the oil do this. As the additive packs break down, so does the oil's ability to keep its viscosity. My theory is to run a 15w50 or 20w50 and don't run the car hard until you see the oil pressure gauge start dropping off of the 5 bar at idle.
i heard this isnt exactly true. as fuel disolves in the oil , especaillly in track use, it breaks down the additives, but the viscosity can actually go up.
they are discussing this issue on the racing threads.
Originally Posted by Snark Shark
Just out of curiosity, is there anything wrong with using 0W 50? I'm thinking since it's the higher number (50) that indicates the viscosity at high temperatures, it should provide plenty of viscosity at high temps, but also circulate quickly on cold starts. Sticking with 15W 50 for now, since it's recommended in the owner's manual, but I doubt 0W 50 was even available back in the day.
yeah, nice to spin a rod bearing on start up..... the viscosity is JUST not there to protect the 928 when warming up.
Originally Posted by Mrmerlin
I would suggest to use Valvoline VR1 racing oil 20 W 50, good on the zinc count and never any issues with viscosity breakdown available at most FLAPS
you have never driven your car hard then.... we saw remarkable viscosity break down with VR1 in scots car... completely gone when we moved to Redline and amsoil.
Another good option is Brad Penn Racing 20w50 but it may not be readily available in all areas. I am lucky to have a distributor close by. It's the old Kendall GT1 oil and used widely in circle track and drag racing world, lots of zddp and phosphorus.
I've been running Brad Penn, in my car, for a few years now and am very happy with it.
This is not exactly accurate. As the viscosity range extends, the warm oil viscosity is reduced. Frex; Castrol 0W-40 has a viscosity of 13.5cSt at 100C, where 5W-40 has a viscosity of 13.9cSt at the same temp. This is true for other vendors and is a function of the additive package and how it affects the base oil. Unfortunately, vendors don't rate their viscosity at low temps, but that's not important for warm oil viscosity.
Ok but the point I was trying to make is that a 0W50 is not a zero weight oil. It only behaves like a zero weight oil when it is cold which is an advantage for cold starts rather than an issue as the oil is closer to the operating temp viscosity from cold.
Ok but the point I was trying to make is that a 0W50 is not a zero weight oil. It only behaves like a zero weight oil when it is cold which is an advantage for cold starts rather than an issue as the oil is closer to the operating temp viscosity from cold.
and in so doing, you consequently made an error regarding the hot oil viscosity. Your compound statement was one part correct, and one part wrong. I only mentioned the wrong part lest people here think that the two oils behaved the same when warm. There have been a couple of mistakes about oils in this thread. Trying to keep it focused.
Ok but the point I was trying to make is that a 0W50 is not a zero weight oil. It only behaves like a zero weight oil when it is cold which is an advantage for cold starts rather than an issue as the oil is closer to the operating temp viscosity from cold.
And the point i was trying to make was that the oil at 0 weight, when cold might not provide the protection you need when the engine is cold. there are engines designed to be able to run 0 weight when cold... the 928 isnt one of them.
08-09-2016, 05:40 AM
