Frequently Asked Questions

What wear numbers represent normal wear?
There is not a set of wear numbers that represent normal wear. There are too many variables that must be considered to establish a set of wear numbers that represent normal wear. For this reason, to provide an accurate report it is imperative that each sample result be interpreted by a trained analyst.
How often should I change the oil?
The answer depends on whether your aircraft is equipped with an oil filter and how often you fly the aircraft. In general, if you have a filter and fly the aircraft at least 100 hours a year, then change the filter at 50-hour intervals. If you fly less than 100 hours in a year then divide the number of hours by two and change the oil at that interval. If your aircraft is not fitted with an oil filter, then change the oil at 25-hour intervals. If you do not fly at least 25 hours in a year, then the oil should be changed at least once a year. This is due to the fact that the humidity in the air when mixed with oil gives off a hydrochloric acid. An additive oil, has a buffer in the oil that keeps the oil at the pH of 7. Once the buffer is used up the oil will become acidic. You can end up with an oil that is eating at your engine.
Why do you recommend cutting the oil filter open along with oil analysis?
Oil analysis has one fallacy, I cannot see wear particles above 8 microns in size. That is the reason it is called wear analysis. The normal oil filter will not hold particles below 25 microns. If a failing part is generating particles above 8 microns, I will not see them but you should see them in the filter. By using both methods you have a fair representation of what is happening in the engine.
If the engine does not have a filter, is there a method to look for particles that will pass through the screen?
Take a one lb. coffee can, fit a paper coffee filter over the open end of the coffee can. With the coffee filter indented into the coffee can, turn the edges of the filter down around the coffee can and attach with a rubber band. Add about a ¼ to ½ oz. of used oil to a pint jar filled about ½ way with gasoline or a suitable dilutent. After shaking the bottle, pour the contents through the filter. You may want to pour some additional clean dilutent through the filter as an additional wash. This will allow you to see a representation of the larger particles in the oil.
Should I be using an additive?
The only time I recommend using an additive is for breaking up hard carbon deposits in the engine. The hard carbon will deposit in the ring groove and the valve guides, creating excessive wear and broken rings. Avblend and Marvel Mystery Oil are both additives that will soften up and remove these deposits. By using either of these products every second or third oil change you will reduce the chances of this type of problem. If the engine currently has a problem with carbon build up, it may require using either product during 3 or 4 oil changes to eliminate the carbon.
Why does low time oil have higher wear numbers?
The new oil is contaminated by the used oil remaining in the engine after draining the oil.
How can I determine if I have plated cylinders on my engine?
Review your engine logbook, the type of cylinder will be entered there. The other method is to look at the base of the cylinders. If they are plated the base should be painted either red or orange.
What will cause an engine to use excessive oil during a trip and then go back to its normal usage?
One reason is that the oil rings have stuck in the compressed position due to carbon build-up in the ring groves, allowing the engine to burn excessive oil during the trip. After the engine is shut down and the engine cools off the oil rings break loose and reseat to the cylinder walls.
Can I have my reports sent or e-mailed to a temporary address?
How often should I send in oil samples for analysis?
For the best results the oil sample should be sent in for analysis each time you change the oil. The reason for sampling at each oil change is that the babbett on the main and journal bearings consist of a thick layer of lead, plated over the bearings base metal and then a thin layer of tin is plated over the top of the lead. Aircraft fuel contains lead in the range of 1700 ppm or greater, (60 ppm of lead in an engine that does not have lead in the fuel will indicate a bearing failure.), so 60 ppm of lead out of 1700 plus ppm does not mean anything. For this reason we cannot use lead to identify bearing wear. Tin is the only element that we can use to identify the difference between bearing and bushing wear. Since the tin is very thin it can be removed during one oil change. If we do not see this removal then when the analyst sees the increase in copper without the increase in tin, he will identify it as bushing wear.
How many hours should I put on new oil before sending in a sample for analysis?
We like to see at least 10 hours but I have been able to provide a complete analysis with as little as 1 hour on the oil.
Can the oil sample be taken cold?
The answer is yes, but for best results the engine should be warmed up before the sample is taken.
Can an engine wear out without showing above normal wear?
The answer is yes if the engine uses the length of time in service to determine removal time. The answer is no if the engine goes to failure before removal.