Beaten-Up Oil Due to High Temperature?

[IanInCalgary]

People have often posted that the oil in their air-cooled bike has been beaten-up by high oil temperatures so they change the oil early.

What are the signs of oil that has been "damaged" by high temperatures?

I do a fair amount of low-speed single-track on an XR250R. The case covers of the engine get amazingly hot - far hotter than any other engine I've touched. The oil doesn't seem any different from the high temperatures.

Ian

 

[daman]

I run two ATV's that you could fry sausage on the side covers, just stick with a quality full synthetic and you'll be fine. Run 'er!

 

[Bud_One]

I had a 1997 XR250R back in 05' - ran nothing but Honda 10W40 Conventional in it. Lots of hare scrambles and national forest rides usually 20 miles at a streach. Never had an issue with the oil . And yes... it did get hot as heck. Only mod was a Yoshimura slip on pipe.

 

[Pontual]

The problem starts when the warm oils is smashed up in the tranny gears and clutch disks. Shearing the 10w40 to a 10w30 and making some crud deposits from broken polymers cooken up on hottest parts. If you do long OCI, you'll get at least deposits and maybe high iron ppm, from engine and tranny.

 

[Quest]

talk is cheep.

Consider doing 1 VOA and a few UOA and compare the values, paying particular attention to the TBN retention part.

That should give you a much clearer picture as to how "severe" the application is treating your lubricant...

Q.

 

[djb]

You impressions of how hot the engine is might be misleading.

The engine is going to be producing an approximately fixed amount of waste heat for a specific load. If the engine feels really hot, it might just be good at transferring that heat to the surface, keeping the inner parts from overheating. If it it feels cool, the interior might be overheating from poor heat transfer.

 

[CONMCK]

Originally Posted By: daman
I run two ATV's that you could fry sausage on the side covers, just stick with a quality full synthetic and you'll be fine. Run 'er!

Are your ATV's liquid cooled or air cooled, (the OP is asking about air cooled), It can make a big difference.
I have seen where air cooled engine oil temps can run in excess of 300 degrees F. 25 hours and the oil is thickened from a 40 vis to a 70 - 80 vis oil.
My liquid cooled ATV's on the other hand is much easier on the oils.

 

[CONMCK]

Originally Posted By: Quest
talk is cheep.

Consider doing 1 VOA and a few UOA and compare the values, paying particular attention to the TBN retention part.

That should give you a much clearer picture as to how "severe" the application is treating your lubricant...

Q.

X2 ^^^

 

[kmrcstintn]

somewhat off subject yet an interesting observation...

my GZ250 is air cooled and is an interesting little critter; if I am doing more stop-n-go traffic the idle bumps up on its own which in turn makes the oil circulate more and transfer more heat out to the surface...if I get an open run as short as 1/3 or 1/4 mile the idle starts to lower before the next stop which tells me that the internals have cooled down; with all the local construction projects that have popped up over the summer I have been noticing this phenomenon more frequently...

for what it's worth I use conventional oil and perform premature OCI's; my current oil change will be the first one that will go past 2500 miles (bought it used last May with 1500 miles...current mileage is 6600-6700 miles and I have been averaging 1250-1750 mile OCI's); might do a UOA to see how bad the oil gets sheared...