Everyone with oil temp issues

wstar

The graph (I'm talking about the one on the left) isn't really specific to an oil or an engine. SAE sets standards for how oil viscosity responds to temperature, which is how we get the standardized ratings like "5W30". That chart simply states the obvious about SAE-standard oil viscosity and heat. It tells you simple truths like "A 15W40 oil running at 250F has the same viscosity as a 5W20 oil running at 190F".

If you're talking about the one on the right, it doesn't even have numbers on one of its axes, so it's clearly just a "feel good" graph trying to show the general relationship between oil temp and engine wear in the general case.

As for the rest of it, re: specifics on what it takes to damage our engine life, and by how much, we're never going to get that data. We'd need someone independent (ourselves?) to pony up several VQ37VHRs and put them on test stands in rigorous testing conditions and destroy them (and figure out the exact relationships between things like X RPMs sustained for Y seconds = Z degrees increase in oil temps). Some people in the bowels of Nissan already have this data, but as usual they don't feel like sharing.

So we do what we can with the standard things we already know about oils and engines, which leads one to believe that even without hitting limp mode at 280, sustaining 240-260-range oil temps all the time is worse for the oil and the engine wear than keeping the temps lower, and it's not hard to fix with an oil cooler.

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