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What causes low magnesium levels on an oil sample?

About a month ago I started to notice that my oil was looking kind of sludgy and had an unusual smell to it. I have also been experiencing some inconstant fuel mileage so I decided to have the oil pulled after appx 6,000 miles and sampled the oil.

I just looked at the sample results today and they have flagged my magnesium levels. The level is at 547 vs 784, 813, 721 during previous samples. I have only had the truck since July.

Since I've changed the oil 12000 miles ago I have not noticed the sludgy appearance. Was it possible I just got bad oil?

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Best I could tell the rest of the oil sample looked fine. There nothing else was flagged, but I suppose that doesn't mean a whole lot.

None of the numbers seem high compared to previous samples when the engine seemed to be healthy (good power, no issues and good fuel mileage) but hear lately it's been inconsistent on the fuel mileage, hiccups around 1200 RPM sometimes and blows black smoke out of the stacks when under demand or using more than half throttle. Going to have my engine shop take a look at it when I get home to see if they can find anything.


Ok, is it an EGR engine? They start doing that at that RPM and usually it's the variable geometry turbo not being able to open and close the veins fast enough to keep up. Good luck!


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Magnesium is an additive metal that is in the additive package the oil company puts in. They probably flagged it because the oil manufacturer has changed their additive package and hasn't told the lab yet.

I'm not sure where the sludgy appearance is coming from but it's not for the magnesium. What else did the sample show?

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Jackie is correct about the magnesium and the turbo. It's not very likely that you have bad oil, there may be something else going on, if you can send me the sample, I'll take a look. send it to:

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Brian Smith will be eternally grateful.
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