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Warning: The before-and-after on our APU oil changes was scary
I work at a regional outfit in Omaha and we switched oil brands on our APUs about 4 months ago. The old oil we used for years left heavy carbon buildup inside the sump every 500 hours. After the switch, I pulled a sample at the 500 hour mark and the inside of the housing looked almost new. The difference was night and day, no joke. Turns out the old oil had a lower detergent package that just wasn't cutting it. Anyone else seen a big change like this from switching lubricants?
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hollym822mo ago
Do you really think that's something to worry about though? In my experience, a little carbon buildup inside the sump is pretty normal and usually not a big deal. I've pulled apart engines with way worse crud that ran fine for thousands of hours more. Unless you're actually seeing sludge clogging oil lines or causing temp spikes, it might just be cosmetic. A lot of these "scary" before and after photos can be misleading too, because lighting and camera angles make old, dry grease look way worse than it really is. Take this with a grain of salt, but I'd wait until you see a real performance or reliability problem before calling it a night and day difference.
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joseph_murray82mo ago
Respectfully disagree - heavy carbon buildup isn't just cosmetic when it starts cycling through your oil system.
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the_sandra1mo ago
That dyno sheet from a 6.7 Powerstroke I saw last month told a different story. 480 horsepower before the cleaning, 515 after. That's a real gain, not a lighting trick. And the oil analysis came back with way less silicon and iron after the procedure, meaning less grit grinding through the rings. I've watched too many guys slap a tuner on a carbon-caked motor and end up with a melted piston to believe it's all cosmetic. The oil flash point was dropping on that truck too, which means fuel was diluting the oil because the rings couldn't seal. You don't get temp spikes or clogged lines until it's already done damage. By then you're pulling the heads off.
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