Is TCP (Triphenyl Phosphate) dissolving the COPPER in your engine? Recent reports indicate that engines using Shell's 15W-50 oil and/or Lycoming's LW-16702 additive suffer from high amounts of copper in their oil analysis. Both products contain TCP.
TCP is a proven high-pressure additive mandated by AD (Airworthiness Directive) on certain Lycoming engines. TCP started out as Tricresyl Phosphate but was reformulated as Triphenyl Phosphate in 1990 due to health concerns. Tricresyl Phosphate is a powerful neurotoxin.
The lubricating qualities of Triphenyl Phosphate are, according to Shell, identical to that of Tricresyl Phosphate. However, Triphenyl Phosphate has a propensity to attack the copper components of an engine - especially in wet engines. "Wet engines" are defined as those that routinely operate with low oil and/or cylinder head temperatures. Both of these conditions leads to retention of water in the engine which aids and accelerates the reaction of TCP with copper.
Shell acknowledges that the use of their 15W-50 results in higher than normal copper readings on oil analysis. However, they state that they have performed extensive tests on copper engine components exposed to 15W-50 and have found no abnormal wear over the lifetime of the engine.
Major copper components, in most engines, include the piston-pin bushings, the tach drive busings (at least on Lycomings), and the rocker-arm bushings. Additionally, copper may be used as an underlayment on the engine's main and rod bearings.
If you suspect that copper is being leached from your engine by Aeroshell 15W-50 or Lycoming's LW-16702 additive then inspect the rocker arms and shafts. If you see a "pinkish" or copper-colored transfer from your rocker arm bushings to the associated shafts then it's more than likely caused by TCP (if not caused by assembly or manufacturing defects). Another place to inspect, on Lycoming engines, are the rocker box covers. Look where the rocker shaft thrust buttons (the teflon buttons) bear against the rocker box. It's common to find copper actually burnished into the rocker box cover by the thrust buttons. Lycoming says that and the bushing to shaft copper transfer are "normal". You decide if it is.
All of the below graphs are derived from the same engine, a Lycoming O-360-A4M which was factory-new in May of 1994 and which entered service in July of 1994. The engine was broken in for 50 hours with both Phillips 20W-50 type "M" oil and then Aeroshell 100 (non AD) oil. After the ring breakin period it was switched to Shell Aeroshell 15W-50 oil until the last two oil changes. Note that in the graphs here I identify the period from 0 to 175 hours as the "breakin period" even though the rings had fully broken in by 50 hours. During this extended "breakin" period wear metals generally trended down until they reached a plateau at 175 hours.
During the subsequent 225 hours, which included nine (9) oil changes and nine oil samples sent for analysis, wear metals remained relatively constant save for a "blip." During this time, copper concentrations were running approximately 25 PPM for a 25 hour oil change - about 1 PPM per hour of operation.
At roughly 400 hours since the engine was new, the decision was made to switch from Aeroshell 15W-50 to Aeroshell 100W. The latter is a mineral-based AD oil which does not contain TCP. The first oil analysis after switching to 100W showed a dramatic drop in copper concentrations. Down from 1 PPM per hour (25 PPM for a 25 hour oil change interval) to 0.26 PPM per hour (7PPM for a 25 hour oil change interval). And the next oil analysis, after the first with 100W oil, showed a further decrease in copper concentration to 0.20 PPM per hour (5PPM for this 25 hour oil change).
The engine was again run with AeroShell 15W-50 oil as a final
confirmation. As the graphs show, switching back to AeroShell 15W-50
produced the expected resurgence of copper contamination in the oil sample.
After each oil change in the above engine the oil filter (a Champion CH48110) is cut open and inspected for metal contamination. The history has been to always find between 20 and 100 tiny copper-colored flakes, each about half the size of a period on a page) in the pleats of the oil filter.
Shell claims that they have never seen actual visible particles of copper liberated by TCP. They claim to only see evidence of copper wear in spectrographic oil analysis (SOAP) which detects wear invisible to the human eye.
However, the last oil change and filter inspection on the subject engine
revealed only ONE speck of copper in the pleats. This is after 50 hours
of operation on Aeroshell 100W. The prior inspection, after 25 hours
of operation on Aeroshell 100W, disclosed a significantly decreased amount
of copper flakes in the oil filter (approximately 10). Now there is
virtually no copper in the filter.
All oil changes have been performed on a strict 25 hour basis and include
a filter inspection and change. The engine is fitted with a full-flow
Champion paper filter. The engine operates approximately 200 hours per
year.
Note how the copper concentration dropped after the oil was changed from Shell's Aeroshell 15W-50 (which contains TCP) to their Aeroshell 100W (which does not). The high copper readings were sustained over nine (9) oil samples, each 25 hours apart. Yet when we moved to 100W, copper concentrations immediately dropped.
Also note that the copper concentration rose back to its previous levels
as soon as the Aeroshell 100W was replaced with Aeroshell 15W-50.
Note that the wear rates of most metals are unaffected by the move
from semi-synthetic 15W-50 to non-synthetic 100W. That is, except, for
copper which DECREASED with the less sophisticated oil. The shaded area
represents the amount of silicon (dirt) in the oil which often correllates
with increased wear.
Note that the LOWEST overall metal contamination figures were reached
while using Aeroshell 100W oil. Overall, the engine is producing less metal
using mineral-based Aeroshell 100W than it ever did running semi-synthetic
Aeroshell 15W-50 with the TCP additive.
The owner of this engine noted what he believed were high copper levels from the onset. The high copper concentrations in the oil, along with the visible evidence of copper in the filter, prompted many calls to the engine manufacturer (Lycoming). On two different occasions, actual filter material was sent to Lycoming for analysis. Both times, the answer from Lycoming was that the copper represented "normal breakin material" and that it would continue to trend down to about 400 hours since new.
Obviously the downward trend ceased at 175 hours, yet Lycoming maintained that this was "normal." It was not until the engine's owner began an independent investigation on his own that the connection between TCP and copper was established. The engine company, despite their long history with TCP, did not know this or was unwilling to divulge it to their customers. Instead, they steadfastly maintained that the situation was normal.
Why is it up to the end consumer to do product compatibility testing for the major aviation manufacturers? How could a major aerospace vendor call nearly 400 hours of visible copper contamination "normal" and how can Shell claim that the elevated copper readings in SOAP do not translate to additional engine wear? Even given the VISIBLE shedding of particles?
Do you have additional data? If so, we're looking for you - especially you Cardinal owners. If you have any additional data or some comments, please Mail US!