Good point. My thinking wasn’t that they would be thicker than an equivalent low VII oil, which is impossible, but that perhaps the VII loaded oils would thin a bit less than one might expect.
How much extra viscosity does 5w40 buy you over 0w20 in the 250-290 degree range?
- Thread starter Lumberg
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The thinning is temperature and shear dependant. Once they have completely sheared they can't thin anymore except by heating up further. But at that time, their viscosity isn't far from the base oil mix to begin with and for high VII oils that will be an extremely thin mixture.Non VII oils are always as thin as they will get for that temperature. It's likely that multigrade oils haven't reached their lowest viscosity at HTHS viscosity measurements. If so, you could reduce the non VII oil viscosity a bit more than you could a multigrade oil (for example, a 5w-40 multigrade with HTHS 3.6 cP vs a whateverW-30 non VII oil with 3.2 cP at 150°C could offer the same protection level under heavy loads).
Really, VII are used to reach a desired winter rating for less $$$$. The rest of the characteristics you have to take with it.
Because it's like $30 per gallon!
Also for everyone arguing, I've run Rotella T6 0w40 in my other track car for a season and the UOAs come back pristine. I keep thinking "Surely this past weekend pushed it over the limit" and Blackstone will come back with something like "looks good, try it for another 6 track days!"
Isn't Quaker State Euro like $22 a jug?
A 5qt jug of M1 is about $26.
I don’t think sump temperature is a good measure of how well an oil is protecting your engine. But it is a useful measure of your engine’s cooling ability.
Yes sump temps go up with viscosity. But whenever I see real data, the thicker oils are always warmer but still thicker than a thinner oil running a bit cooler in the same engine. Member Shannow did some direct measurements a few years ago.
A very useful metric is the HTHS (high temperature & high shear) viscosity, measured at 150 C (~302 F) and at high shear rates. To me this better represents the oil in action, protecting your engine.
Yes sump temps go up with viscosity. But whenever I see real data, the thicker oils are always warmer but still thicker than a thinner oil running a bit cooler in the same engine. Member Shannow did some direct measurements a few years ago.
A very useful metric is the HTHS (high temperature & high shear) viscosity, measured at 150 C (~302 F) and at high shear rates. To me this better represents the oil in action, protecting your engine.
Yep, close enough.
This tread is worth a look, Shannow goes into detail of heat flow and temperature in a IC engine.
Oil's part in cooling engine
is there a %of how much the oil cools an engine bedsides the radiator? for example the oil is cooling 15% and the radiator85% can such a thing be determent and if so does syn oil cools more than blends or conventionals? tnx
bobistheoilguy.com
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