Different Take on Overheating Issue

Lug

The article I read on the bearing problem noted 300 degrees as point break for Nissan. I have to assume the 280 degree limp mode is just a bit of cushion. As far as general oil breakdown at what temp, I really am not that well versed in oil theory to make a call.

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Modshack

Nor is anyone else here. The Panic is all based on emotion, not fact...

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wstar

It's not a binary proposition though, there's a lot of room between "Panic" and "Everything's fine shut up". Oil breaks down under heat stress, reducing oil life. Oil viscosity drops as heat rises. Engines like to have good oil at a good viscosity to prevent excessive wear (or in very extreme cases, immediate parts failure, although I think you're more likely to run into detonation issues from overheated cylinder walls first). If you plan to keep an engine for a long time, and it's hitting high oil temps on a regular basis, you should put an oil cooler on it. It's pretty simple.

What's high enough to worry? We don't know and never will. We can put some boundaries on the issue though. Nobody thinks 200F oil temps are bad for a car, that's plenty cold. Nissan clearly thinks 280F+ is bad because the ECU kicks into a safety mode and limits revs in that range. I think if you're peaking at 260+ on any kind of regular basis, or sustaining anything over 250 for long periods, you would probably be better off with an oil cooler in terms of long-term engine wear issues, but that's just my educated guess.

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kannibul

But, is 260F where oil starts to break down, or is it higher. If oil has issues at 350F - then the "weak link" would obviously be the bearings.

200F might very well be too cold - the oil might still be less than 30w oil, as far as it's viscosity is concerned.

kannibul

That's what I was getting at