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Pro tip: I swapped to a 5W-40 synthetic in an old 7.3 Powerstroke and it got louder
My '96 F-250 with the 7.3 was always a bit noisy, but I figured a full synthetic Rotella T6 might quiet it down. After the oil change, the injector clatter actually seemed more pronounced for the first hundred miles or so. It smoothed out after that, but it taught me that switching oil weights on high-mileage engines can have some weird break-in effects. Has anyone else in the Midwest run into this with an older diesel after an oil change?
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pat_schmidt716mo ago
That's just the injectors cleaning up, not the oil weight.
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claire_walker6mo ago
Pat, you've got part of it right about injectors cleaning up, but oil weight absolutely plays a role here. Thinner oil can reduce engine drag and let things spin more freely, which changes how the engine sounds. The noise difference isn't just in your head. It's a combination of both factors working together, not just one or the other.
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robert_anderson696mo ago
Actually saw a video from a mechanic who tested this. He put different oil weights in the same engine on a dyno. The sound change was real, and so was the tiny power difference. It's not just injectors. Thinner oil flows faster and reduces drag on moving parts. That changes the noise you hear. Both things can be true at once.
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