High mileage oil?

One of my bikes has over 94,000 miles on it, of which I put on about 13,000. The engine may have been rebuilt in the past, but I do not know if the rebuild included new bearings. Since it is far easier, it seems most likely to me that the PO only did new rings and a valve job. On a car, it is easy to check the oil presure, and thus tell if the main bearings are in decent shape. (If the pressure is good, that means the bearing clearances are not excessive -- outside the wear limits specified in the workshop manual maybe, but still not totally excessive.)

Anyway, this is just a long winded lead-up to determine if any of the more experienced guys here think it might be a good idea, for the longevity of my engine as she now exists, to switch to a higher viscosity oil, or to an oil designed for older, worn engines? I ride year round, but here in the San Francisco Bay area the temperatures are temperate -- almost never less than 40 F, nor greater than 80 F. I do not race, but I do not baby the bike either. I ride at freeway speeds daily.

I would like to get to at least the 100,000 mile mark before I tear into the engine and do a full rebuild. As she is now, she has good compression and power, but makes a little cam chain noise (which I am going to try to reduce by using a better tensioner), and clunks a little when shifting (which I can live with).

Waddayathink?

Post edited by: apeman, at: 2005/11/27 01:34

What viscosity oil are you running now and what is your usual oil change interval ?

If the engine has lasted 94K miles on a diet of 10W40 and is not make "terminal" type engine noises, then I'd be surprised if it did not last another 6K on the same oil.

If it was mine, I'd probably just change the oil every 2K miles instead.

Post edited by: Murphyau, at: 2005/11/27 04:10

what he said!

I used Castrol GTX 10w40 in Winter, 20w50 is Summer and got 165,000 miles out of my 78 KZ650 and never touched the bearings. As I've mentioned in the past though, the engine went downhill bad the last few miles of it's life, even with oil changes every 2000 miles as always since I bought it new. The last time I tried to change oil the oil was sludge and would not even drain out of the pan. I will always blame the change in formulas of the "SF" "SG" ect. I believe something drastically wrong with the way the newest formula of Castrol worked in a motorcycle engine. The reason I think this is I had virtually no sludge until the end, where all of a sudden that's all there was. Strange I thought.