I recently had a question from a pilot who had a quantity of Phillips 20W50 oil that was 12 to 15 years old. He was wondering if it was OK to use in his airplane.
As with so many other things in aviation — and in life — the answer is not a simple yes or no.
The legal answer is that an oil company must guarantee that its product meets the specification for at least three years. This is in the ASTM spec under storage stability.
So that is one answer.
The other question is whether the oil will technically meet the requirements of your aircraft engine after this length of time. Now this is more of a gray area.
The two concerns after this length of time are moisture and additive settling.
If the oil was in sealed containers and stored in a dry area, it may be OK.
But I know that even sealed containers can take on water.
I would recommend that the pilot decant the oil into a clean container.
If you see any moisture or milkiness, either do not use the oil or try heating it up until it is clear.
Also, while you are decanting the oil, look closely at the oil, especially the last amount out of the container and then look in the empty container for any unusual change in appearance or consistency. This would be an indication of additive separation.
More than 25 years ago, Shell had a problem with one of the additives settling out of its 15W-50, but I have not seen much since.
Also, Phillips had that X/C II oil that contained a zinc additive that caused problems. If it is that product, I would recommend against using it.
The bottom line is that most aircraft engines are approved to fly on mineral oil, so as long as the oil is not milky and looks normal, it can probably be used.
Hello Mr. Visser. I tried to contact you but maybe my Mail went into your spam folder. I’m recently having a debate with a Youtuber called Matt who owns the channel “Dirty Garage Guy”. He’s English and mostly very accurate when critiquing other Youtubers. Recently though he critiqued the channel “Driving For Answers” (D4A) on his video about poppet valves and lead in fuel. D4A made a comment about people putting lead in the fuel in the 50s and 60s also to protect the valves. Now Matt said that this is nonsense since initially lead was just an anti-knock agent and attacked D4A for spreading misinformation. You yourself mentioned that this myth is quite widely spread. Therefore I would like to know a few things:
When were the people in the industry aware for the FIRST TIME that lead protected the exhaust valve? Matt claims it was only after the fact. He says in 1972 Japan introduced unleaded fuel and american cars suffered valve seat damage. Only then people knew that valve also protected the valve seats. What are your thoughts on that?
Is it correct to call it valve recession? Matt claims that it is valve erosion not recession although I found a few SAE papers also using the term “recession”.
From Ben Visser: It is called recession because the exhaust valve recesses into the head. in the 1920s and 1930s, the engines were not as highly loaded and operated at lower rpms so recession was not that big of a deal. They knew about recession so used better materials to solve the problem. Then as the need for higher compression and performance, the oil companies introduced lead to raise the octane to keep the knocking under control. this solved the valve recession problem and the engine manufacturers used less hardened seats. In 1971, GM started making unleaded fuel compatible engine with induction harden seats. Shortly there after the other auto manufacturers followed suit because of the introduction of catalytic converts in most cars in 1975.
Ben
Throw it away! It’s not worth the risk.
I think the question would be; would you bet your life on this oil?
No indication as to whether this was a case of oil in Qt-cans… or a steel barrel.
Small cans are easier to assume ‘how-they-were-stored… and thus ‘inspect’… relative to a steel drum of oil.
Hmmmm… one very important point to remember: Spec-lubricants [and solvents, fuels, etc] are dirt cheap compared with a smooth-running reliable engine in-flight… which is priceless.
Two thumbs up.
Why not just send a sample taken 1-1/2 – 2 inches from the bottom of the barrel for analysis? Ask for the FULL report not the synopsis.