Does Mobil1 really protect to 400degF??

[Tyrolkid]

I was reading the back of the Mobil1 0w-40, and it states that it "protects to 400F"

. How true is this? Why is everyone so worried about oil temps in the 280-300 range??

-Mike P

 

[Dr. T]

Most likely, yes...it will protect at this temp.. This would mean then that temps. of 280-300 are a big deal. However, I believe there are local spikes of temperature that are much higher than this...especially when shutting the car off during extreme heat with no oil or coolant circulating.

 

[unDummy]

What temperatures do the bearings melt?
Your engine is toast before the average oil temp hits 400F.

 

[jason07-1zzfe]

quote:

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Originally posted by Tyrolkid:
...How true is this? Why is everyone so worried about oil temps in the 280-300 range??

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Because all oil thins with temperature. About every 30F the oil thins enough that it would be equivalent to you running the next thinner grade. So if your normal OT is 200F and you run 30wt oil. At 290F you oil will be about as thin as if you were running a 5wt!
Protect is a bad choice of words because it will protect much less because it has thinned significantly. They just mean that it won't all volatize off and coke up severely. By the way, before supersyn, they used to say up to 475F. FWIW.

 

[Scott_in_WI]

Actually, some locations within the engine will exceed 400°F. The following is a table from a paper by Roy Howell, Chief Chemist, Redline Synthetic Oil Company, Formerly of Lubrisol:

code:

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Engine Temperature Chart (F)

Upper Cylinder Wall 300 - 500

Exhaust Valve 1200 - 1500

Piston Crown 700 - 800

Hydraulic Valve Lifter 250 - 300

Crankcase 200 - 300

Top Ring 300 - 650

Exhaust Gases 500 - 1000

Combustion Chamber 3000 - 5000

Coolant Jacket 165 - 230

Connecting Rod Bearings 200 - 375

Main Bearings 200 - 350

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