Q: I have a Lycoming O-360-A1A that had a prop strike and was rebuilt at Western Skyways. I was told by my test pilot to change the oil after five hours of flight.
Is this correct? If not, at what hourly interval should I change the oil to safely monitor the break-in?
Chuck Hohos
A: Chuck, your question is one that is easily answered and I hope many of our readers will follow the information provided.
The best source for your question can be found in the latest revision of Lycoming Service Bulletin 480.
I certainly can’t argue with the suggestion that you change the oil after five hours of flight, as long as you also inspect the oil filter element or oil pressure screen in addition to inspecting the oil suction screen in the oil sump.
Even though Lycoming suggests the first oil drain be at the first 25 hours, I prefer the five hour drain and filter and/or pressure screen inspection.
I feel that oil is one of the least expensive things you can put in your engine and this first five hour inspection will give you peace of mind knowing what’s going on in your engine.
Your future oil change frequency depends on whether you have a full flow oil filter or just a pressure screen. If you have a filter, the interval for changing oil and the filter is 50 operating hours or no longer than four calendar months. With a pressure screen, the interval is reduced to 25 operating hours, but still at four months.
The primary reasoning behind the calendar time requirement is to remove the engine oil that is contaminated with condensation and the by-products of combustion that contribute to internal engine corrosion.
Also, don’t forget to inspect the oil suction screen located in the oil sump.
GREAT ADVICE The reason for changing oil after 5 hours following a rebuild is that there is bound to be some junk floating around in the oil from the process of rebuilding the engine. Honing the cylinders can leave some debris and abrasive particles imbedded in the cylinder walls that will soon flush out with normal operation. Any excess sealant, plus minute particles from the normal wear-in / break-in process will be there too. Getting stuff like that out of the oil is best done sooner, rather than later. Your oil filter is going to trap most of the debris, but you don’t want to wait for a very cold day where your oil is so thick initially on startup that the pressure relief valve opens and allows unfiltered oil to circulate.
And as Paul says, don’t forget to cut open the old filter and examine the filter pleats for trapped contamination. Don’t get too excited if you find a very small quantity of STUFF immediately after rebuild as long as your NEXT oil change at the normal interval, the filter has quite a bit less STUFF trapped in the pleats.
If you are going your own work, after you examine the filter pleats, stuff the oily accordioned mess into a clean baggie for your A&P mechanic’s review and opinion about the trapped contents.
Jerry King
The accordion mess can be wrapped in a few paper towels to absorb the oil. Wrap it tightly in one towel. Then wrap it in a few more. Then wrap a few rubber bands around it and put it in a plastic baggie. A day later the filter pleats will be ‘dryer’ and it’s easier to see any particles there.