I'm not familiar with extended warrantys, so take what I say with a grain of salt. I'm thinking if you could find a reputable company that would cover the diesel engine fairly comprehensively at a reasonable price, it might be worth the gamble. A lot of repairs on trucks can be done for less than $3,000 which even though that's not pocket change, it wouldn't send most of us to the poor house and we could move on fairly painlessly. However, there are a lot of repairs on diesel engines that can easily exceed $5,000 and maybe even approach $10,000. That wouldn't be such an easy pill to swallow. So if I had a diesel and could get a good quality warranty for say, 100,000 miles beyond the manufacturers warranty for a reasonable amount of money I think I would do it. Perhaps some warrantys would let you pick a high deductible for less expensive coverage, allowing you cover the less expensive, but more likely repairs.