6000 mile oil damage

[Tmoose]

Over on the SAE forum someone posted " Has anyone noticed the damaging effects that the new 210 degree F thermostat presents? The bearings are running so scorching hot that full-synthetic oil blends are being burned black before 6000 miles. Yikes! "

1 - A couple of buddies have pretty new cars, and I don't think they mentioned "black" oil when changing.
2 - I don't think that bearings are the high temperature location in a passenger car engine.

Am I missing something?

 

[TheBlacksmith]

Sounds suspicious to me. Cars have been running 205 degree thermostats and 5000 mile oil changes for years. I find it hard to believe that 5 degrees and 1000 miles goes over the cliff.

 

[romke]

to me it seems rather unlikely. bearing temperatures need not necessarily increase when a higher temperature thermostat is used, although it might effect overall oil temperature somewhat and oil temperature in the piston ring region. what exactly is meant with synthetic oils being burned black? do they blacken due to the inclusion of oxidation products, do they increase in viscosity, does the viscosity index go down, or are they just keeping soot in suspension, as they ought to do in diesel engines?

be aware that not every full-synthetic oil is of the same quality - what matters are the specifications of the oil in terms of viscosity and performance. are you sure that the correct type was used in the incidents reported?

 

[Tmoose]

100% word of mouth - the statement struck me as odd,but I don't have much dealings with cars newer than 2000 somehow

 

[dicer]

Synthetic oil was originally designed for jet engines if I remember correctly, and those temps far exceed anything a piston engine will see unless its a full adiabatic with no cooling system. The problem is the ridiculous low viscosity spec'd, at temperature SAE 40 pours like water.
And your buddies should not be changing their oil, if there is a problem the dealers will not honor the warranty, and say there is no record of oil changes. The internet is rampant with stories about such things.

 

[Overrun]

Black oil is usually suspended carbon and such. Burned oil is thick and gunky.

http://www.eng-tips.com/

 

[drwebb]

Like they said, color alone tells you squat. Back when I formulated oils I ran some short tests in a shared-sump motorcycle on different blends, and then stored the used oil for awhile. Most oils were clear with dark residue (clutch debris) settled on the bottom. One that included a powerful dispersant was black with no residue. Thereafter I always included that ingredient in oil for my own bike, but couldn't consider it for commercialization as customers would say the oil turned black so quick it must not be any good!

Separately I analyzed different factory-filled automatic transmission fluids with lots of service miles on them- some of the darkest ones retained better clutch performance than lighter ones.

Automotive engine oil formulations are generally about as analogous to jet engine oils as laundry detergent is to non-chlorine bleach, btw. There may be a little commonality in ingredients, but they're designed for much different purposes.