[macgyver]

After 2 years and 5100 miles since the last oil change and the point at which I switched to Rotella T6 full synthetic oil I have sent an oil sample in to Blackstone for analysis. Forest had previously used them so the results ought to be comparable. The numbers for the wear metals were all similar, with my iron results being in the middle of his three sample's numbers. From the records it appears he changed oil annually.

The TBN (Total Base Number), the ability to neutralize acids dropped from 10.6 to 7.9 so there is plenty of reserve left. The viscosity is in the normal range according to Blackstone with minimal if any change.

The iron results are just over a third of amount that Detroit/MTU states as the limiting value for iron in the oil.

My oil consumption has been undetectable. Shortly after the switch to T6 I added 2 quarts but nothing since and the level appears constant.

On the basis of these results I'm planning on keeping the oil for one more year before changing. At this rate the T6 will be cheaper per mile than annually changing the straight 40 weight designated for 2-stroke Detroits and more readily available on the road (though with my consumption that appears irrelevant). One could run the same test as I did, including the TBN, and find that annually changing the straight grade is overkill. The results Forest shared with me hint that that is quite possible, but he didn't get the TBN test.

I hope this helps as we move forward with these quirky 2-strokes.

I had my first oil change when I bought my 87 with the silver 92 ddec, and was quite suprised it took 36 litres . They said the oil should be good for 20,000 miles , I have about 6000 on this oil and plan of leaving it for a lot longer, hopefully that won't cause in problems ? Don