Oil Analysis - High Silicon

[bobk]

Looking for comments, advice. Engines are 6V92TA's, 1981 425 hp. Total engine hours are around 5000.

I just did an oil analysis out of curiosity since it has been a few years. The recently rebuilt starboard engine (about 800 hours SMOH) showed 7 ppm silicon, the older port engine (2800 hours SMOH) had 33 ppm silicon. Both engines had about 180 hours at 1000-1100 rpm on the oil. The port engine got a new rear main seal and bell housing 180 hours ago when the Allison M15 was re-sealed.

The analyst as well as my mechanic say the silicon is 'dirt' and recommend no other action than resampling after 100 hours. Iron, soot, fuel contaminants are all normal as is TBN.

Any thoughts re the source of the silicon? Both engines have freshly cleaned Air Seps.

Bobk

 

[MikeP]

We used to do a lot of oil analysis on engines and, as the analyst noted, the source for silicon is usually dirt/dust which means it came from outside the engine. Typically it's because of poor filtering, a broken air intake hose/connection or an engine that was rebuilt and not kept clean during assembly.

I don't know anything about air seps, never having used them, but when we did testing on engines using different type air filter material, engines that used K&N-type filters usually showed higher silicon content in their oil samples than engines with paper air filter elements. Air seps appear to me to use a K&N type filter but I don't know if that is the case.

IMO, if other elements of the analysis show normal, I wouldn't be concerned about the silicon. True, dirt in the engine can caused increased wear but increased wear should be accompanied by an increase in other elements in the analysis. Since there is no such increase, it would appear that the dirt particles are not large enough to cause a problem.

Also, was this test a single "first time" test or part of a series? Single tests are not really all that valuable. The best use of an oil sample is based on regular samples that can then identify changes. Since the engine was recently rebuilt, the dirt could have been from the rebuild procedure and a subsequent test may show the silicon level to have dropped after the first oil change, indicating that the "assembly dirt" was removed with the oil change.

 

[Genesis]

Oil-impregnated gauze "filters" are crap. Every time someone actually bothers to run a real test this is what comes out of the results. Unfortunately the "Airsep" (and look-alikes) all use oil-impregnated media.

This has turned into a REAL problem with vehicles that have MAF sensors as what gets through the filter will trash them. A bunch of ricer boyz keep replacing $200 MAF sensors without realizing that they're destroying them by having that "cool" red air filter under the hood.

The best option if you need to use them is to get and keep the ER as clean as you can to reduce the amount of dirt being blown and sucked around in the engine room. It's not great but on a marine engine there's less dirt in the airstream in general then there is for a road (or worse, off-road!) vehicle.

The additional grit does cause wear and can foul inter and aftercoolers when mixed with the normal amount of oil vapor in the crankcase vents, but other than finding a way to use paper media keeping the ER clean is about the best you can do.

 

[captddis]

Looking for comments, advice. Engines are 6V92TA's, 1981 425 hp. Total engine hours are around 5000.

I just did an oil analysis out of curiosity since it has been a few years. The recently rebuilt starboard engine (about 800 hours SMOH) showed 7 ppm silicon, the older port engine (2800 hours SMOH) had 33 ppm silicon. Both engines had about 180 hours at 1000-1100 rpm on the oil. The port engine got a new rear main seal and bell housing 180 hours ago when the Allison M15 was re-sealed.

The analyst as well as my mechanic say the silicon is 'dirt' and recommend no other action than resampling after 100 hours. Iron, soot, fuel contaminants are all normal as is TBN.

Any thoughts re the source of the silicon? Both engines have freshly cleaned Air Seps.

Bobk

Not just dirt but everything else is included, like gasket sealer, hi tack, silicone sealant etc.
Run it and resample.

 

[bobk]

Not just dirt but everything else is included, like gasket sealer, hi tack, silicone sealant etc.
Run it and resample.

Thanks, I wondered if silicone sealers would show up as silicon. Will resample.

Bobk

 

[Genesis]

Yes they will and will drop over time if that's the source.

 

[davidwigler]

Time for an oil change?

 

[bobk]

Time for an oil change?

Indeed. We run about 350 hours a year and change twice a year. Other than the silicon, I suspect the change frequency could be extended, but it will be done next week.

If anyone would like to see what that analysis looks like after a lot of low rpm operation, I'd be happy to send it. I don't think I can attach it here.

Bobk