Saturday, September 19, 2009

Do Aftermarket Oil Additives Reduce Wear Metals ?

John, I have to say that I'm really impressed!  You are right on both counts!  It was oil streaking in the bottom of the aircraft cylinder, and this was the first sample since I started using XYZ oil additive.  I've never been a believer in oil additives before, but all the reading I've done says that XYZ helps protect engines that don't fly a lot.  I don't think that the additive has anything to do with the metals being high, as they were high before I began using it.  I'm almost to an oil change, so will be interested in seeing what they do this time.

Customer picture below taken of a chrome cylinder barrel through a boroscope with oil streaking. Notice the wavy little lines (channels).

I wouldn't use metal ppm (oil analysis) to make a judgement on the effectiveness of an EP (extreme pressure) additives, such as phosphorus in aircraft engines. Their function is to prevent micro-welding between two metal surfaces during periods of metal-to-metal contact. They do not provide protection by keeping the surfaces separate, as oil does. (Of course, additives might have multiple functions, such as corrosion protection which would help to reduce iron levels.)

EP additives protect surfaces during those periods when the oil film is breached. They do this by reacting with the iron at high temperatures created by friction and oxidizing the surface. This oxide film prevents micro-welding which leads to spalling. The act of protection does cause a micro amount of iron oxide to form which eventually ends up in your oil analysis; whereas chunks of metal from spalling are too large and do not end up in the oil analysis. Thus erroneous conclusions about their effectiveness when only using oil analysis to judge their effectiveness or lack thereof. Who cares if a few ppm of iron is oxidized from the surface in the act of preventing a chunk from being torn from the surface!

Normally, high levels of EP additives are used in gear box oils and hydraulic oils, such as 5606, but not in combustion chamber oils as the act of bore polishing is detrimental to a honed surface (which is not a concern in your engine with channel chrome cylinders).

No comments:

Post a Comment