I have a high mileage 84 300 SD, 384Miles. Chain stretch is almost nothing. I attribute this to full synthetic oil since available. Lots of oil filter changes. Not running the oil too long. 55 miles each way on the freeway almost every day and what I think the most important chain saver. Avoid high RPM. I drive just under 3000 RPM on the freeway. with the 2.88 dif. that gives me around 70 mph.. Fast enough for me.

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1984 300SD turbo 126
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God made me an atheist and who am I to question His wisdom