In oil analysis, where does the iron come from?
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Patman
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The LS1 engines have aluminum heads and an aluminum block however like all (or at least most) aluminum engines they have iron cylinder liners.
The method of using a very high silicon content aluminum in the blocks, and then etching the bores so that the bore surfaces are essentially nothing but the polished silcon, has proved very durable. This non-liner approach was pioneered by Porsche with the engine in the 928, and later used by Merecedes beginning with their last generation of V8s. I'm surpised more companies don't go to this production method.
This is the method that GM tried with the Vega engine back in the 70s. Unfortunately, technology was such back then that the bores could not be uniformly rendered and we all know what smoke monsters those things were. MB has never had that problem and I've personally seen a MB V8 (3.8 litre) with over 300,000 miles on it that didn't smoke and used only a negligible amount of oil.
Well you can get plenty of rust over night. Drop a nail in water and look at it the next day. I'm sure setting around for long periods of time probably contribute to the higher iron samples during the winter, because the water is not burnde off. But I wouldn't loose any sleep over it
Yes there may be some surface oxidation, but I would use a good oil with a decent TBN and not sweat it.
Most Fe alloys don't rust quite as fast as some mild steels. And most steel contact surfaces should have some remainder of lube to prevent surface oxidation. Relax.
The sodium content on my oil analysis went from 16 mostly summer to 36 mostly winter. I am sure that some of the salt fog I drive through out on the tollway gets ingested and thats where it comes from. The iron ppm went up slightly with a few less miles so I figure the salt does do some corroding of internal parts.
All motor oils contain corrosion inhibitors, so don't worry, and the better oils have more effective inhibitors. The thin film of oil remaining on all your internal engine parts protects those parts.
Rust is very abrasive. If internal rust was a problem, lots of us would be in trouble, and we aren't (at least not in trouble from this problem
Ken
The S2000 engine used a fiber reinforced matrix FRM (I think it's a carbon ceramic) right in the aluminum casting. This produces a high wear surface yet excellent heat transfer because it's filled with aluminum and is part of the aluminum block. The main reason they do this is to get the largest bore possible on a given bore centerline spacing (iron cylinder liners take up space). Unlike the Vega, the high oil consumption tends to be on the front end of the engine's life, not the middle (which quickly becomes the end.)
[ February 02, 2003, 10:59 PM: Message edited by: S2000driver ]
[ February 02, 2003, 10:59 PM: Message edited by: S2000driver ]
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