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Appreciation post: That old diesel mechanic I talked to at the parts counter changed my mind about oil weights.
He told me to stop using 5W-30 in my 2005 F-250 and switch to 15W-40, and after running it for 6 months I finally see why he was right, has anyone else had an old timer give you advice that actually worked better than what the manual says?
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the_lee1d ago
Man that hits close to home. Had a similar thing happen with a guy at a NAPA in BFE Wyoming who talked me out of using synthetic in my old 7.3. Said those injectors need the extra zinc and that thin oil just lets everything rattle apart. Stuck with his advice and my truck has been starting better in the cold and doesn't sound like a tin can full of marbles anymore. Funny how those old cats just know from years of wrenching what the manual writers never bothered to learn.
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davis.noah22h ago
Hang on, you mean he talked you OUT of synthetic? No way, I thought that was the holy grail for everything with an oil pan. I've never heard that about the zinc thing, but it makes a weird kind of sense the way you describe it. I guess those old school guys just saw what the friction modifiers were really doing to the internals after ten years. That's wild, wonder how much money I've wasted on fancy oil over the years.
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Oh man, @the_lee said it perfectly about those 7.3s needing the zinc. My wallet is still mad at me for all those years of fancy synthetic when plain old dinosaur juice was the real answer. Guess the manual writers never had to actually fix a worn out engine at 3am in a blizzard.
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