How can I detect bearing damage caused by oil?

Question

After reading this question I used 0W-30 instead of 0W-20. Is it serious? and Paulster2's reply:

One of the issues with running a heavier weight oil is that your bearing clearances are set by the factory to accept the thinner oil. By having the thicker oil in the crankcase, you run the risk of bearing damage. I think with where you live the chance is mighty small, but it's still there. If your car is really new, I'd highly suggest you change the oil out. When a car is newer, the bearing tolerances are even tighter.

Now, here is the story. I bought my first vehicle, a brand new bike ('17 crf250l). I went to the official honda dealer for the 1000km oil change. Mechanic said that he put 15w50 instead of 10w40 because we were in the summer. I do not oppose as I assumed he would know what he was doing. However, summer passes and I do the next oil change in the following winter with a 10w40 at 4000 km. Like a year and 5000 ish kilometers later I realise that the translation of the owners manual was faulty (probably intentionally) with 3 times more frequent oil changes and the suggested oil was 10w30 not 10w40. Kilometers might be low but I must point out that this is a 250cc engine that revs up to 11000 mark and with usual driving rev of 6000s. Also it is made to be taken offroad and I have did so many times. As you understand from the story, I know very little about mechanics and try to learn it through manuals. Hence I have no real experience in diagnosing. Should I expect any bearing damage now or in the long run? If so how would I understand if there is any problem present? Should I get 10w30 oil asap? (Sorry for spelling errors. I am on a borrowed computer and I do not have my grammar checker.)

Answer 1

I would guess you do not have a problem but stay with manufacturers recommendation. Newer engines with small bearing clearances need low viscosity oils to get the right oil flow across the bearing for proper cooling. For a tin babbit ( typical tri-metal bearing; steel back, bronze middle and babbit surface) at a temperature of 250 F, the fatigue strength is significantly higher than at 300 F. A tin babbit with some lead has a eutectic melting temperature of 361 F . That is an example only because many different alloys are called "babbit" and without a specific composition any numbers are speculation . I am sure no one at a dealership knows any more about the bearing alloy than any info on the box.

Answer 2

Get a used oil analysis done on your engine by a company like Blackwell. I believe NAPA does them too. High levels of lead and other materials in plain bearings will indicate bearing damage.

Pistons are aluminum, rings are iron, cylinder walls may be iron or some kind of cyramic coating. Roller bearings will be iron with maybe brass or plastic cages.