Different Take on Overheating Issue

Lug

Limp mode was initiated because they changed their bearing design by dropping lead from the formulation (think eco-friendly). This meant that at temps above 300, the bearing would start breaking down faster than the older design. They noticed this and instituted the limp mode as a protection feature.

__________________
keep Chubbs in your pocket - Chubbs

chubbs

Thanks Lug - +1 rep

__________________
.

'03 Grey >>> '06 Black >>>'10 Silver >>> '16 Grey ^

kannibul

While true, then I assume it'd also be true with other cars that don't have an oil temp guage there for the driver to see.

For example, how about on the G37? Same engine, but AKAIK, no oil temp guage. Are they complaining as much about oil temps getting over 200F?

Why is 200F bad? or 210F, 220F, 240..260? At what point does oil become less than what it was 10F cooler? How long at 260F does it take for the oil to have measurable degradation? How many miles/months does that translate to for the average driver?

All that...lol

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.

__________________
keep Chubbs in your pocket - Chubbs

Modshack

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

__________________

Steal my car! (SOLD)...Now Porsche Cayman S
Oil Cooler DIY: Here!

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.

__________________
7AT Track Car!
Journal thread / Car setup details

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