Quote:
Originally Posted by ForcedInduction
25k miles is too long for ANY diesel engine, especially a high emissions IDI engine. You must do an OA to determine the soot load your engine puts on the oil to know how long its safe to use the oil.
The oil brand, type and weight doesn't matter, none of it changes the soot deposit rate of the engine. Once it gets to 4% load, you're putting the engine bearing's life on the line.
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Don't fully agree with you here. Different oils have different degrees of ability to hold soot in suspension. For instance, if you were using a gasoline-engine oil in your diesel you would have a very limited oil life due to those oils' not being designed to deal with diesel soot deposits. Conversely, if you are running a high-quality diesel-rated synthetic oil, and your car is running properly (aka cleanly with good compression and injectors) and you are not blowing black smoke like a tire fire at all times (Jason's car need not apply
), and you are using modern ultra-low-sulfur fuel or better yet biodiesel or some blend of the two, AND you are using the engine as it was designed to be used (longer-distance driving, long periods of running at operating temp, not quick hops around town), AND you are using a high-quality filter, I see no reason why your oil should not last 20-25,000 miles.
If you are not following the above directions, though, then even changing it every 3000 miles may not be enough to protect your engine from premature wear. I think with diesels the engine's long-haul longevity and health have as much or more to do with the pattern of how they are used as how they are maintained. You can have one that had the oil changed every 2500 and all maintenance done by the book that is completely worn out by 100k, or you can have one that had the oil changed every 10,000 and the maintenance slacked off a bit, but driven on the highway, and still running strong at 300k. All depends on the pattern of how and when it was driven.