In search of better oil analysis

edited February 2023 in General Discussion

Years ago, and despite frequent use of my aircraft, the oil analysis reports were mediocre. About 5 years ago, I began doing 4 things that dramatically changed the report numbers, and put them into the normal range. Here are the tips, in no particular order.

  1. I spoke with an engineer who worked in the oil industry. He did not work for them, but said that Phillips had an excellent aviation oil and additive package. Switched to Phillips XC. The same engineer had a lot of good things to say about Cam Guard, no matter which brand of oil you choose for your engine. I've been using Cam Guard in my engine for a long time, and will continue.
  2. This one has been mentioned on this forum by myself and Scott numerous times: After every flight, one of the first things I do after engine shutdown is to pull the oil dipstick, which allows the steam (a byproduct of combustion) to escape from the crankcase. If not let out, that steam can condense into water and can cause internal rust and/or contaminate your oil.
  3. During the winter and transitional months, I leave the Tannis heater plugged in 24x7. I realize there is a war being raged on the internet regarding leaving the Tannis plugged in vs not, but the bottom line is this: if the engine remains substantially warmer than the ambient temperature, the interior of the engine cannot reach the dew point, which means water cannot condense, which means no internal rust and/or oil contamination. Benefit: whenever I go out to fly during the winter, the oil is already warmed up, and a pre-heat is not needed (that's the purpose of an engine heater!).
  4. Whenever you fly, fly long enough to get the engine and oil temperature up to at least 180 F. That temp is high enough that any water in the oil will begin to evaporate.

These 4 things listed above have made a huge difference, and my engine oil analysis reports are proof.

If you have any other tips, feel free to share them. I'd like to hear from anyone who uses an engine dehydrator. I'm considering adding a dehydrator to the list of things I do to preserve the life of my engine.

Jim "Doc Griff" Griffin
PA28 - 161
Chicago area


  • From the not arguing and just pondering standpoint, based on noted actions, a dehydrator seems like adding suspenders when already using a belt. Definitely would love seeing some sort of test results as to whether taking this step (on top of the others) shows a benefit, or whether one-or-the other is equally as effective. Or, perhaps using the pre-heater during winter, and dehumidifier when not using the pre-heater. Naturally, this presumes electric supply at the hangar, which is a luxury for some. 😋

    For the dipstick trick, am presuming that it only remains open for some duration and then closes again prior to leaving?

  • Regarding the dipstick: When I land and get out of the plane, the oil is very warm. On my Continental TSIO-360 the dipstick is different than the oil cover. I take off the oil cover (you take off whichever you can) and steam pours out. I then move the plane back in the hangar, lock the door, plug in the battery tender and the out-steaming is done and I put the oil cap back on. I don't leave my Tanis plugged in all winter. I'm pondering that.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Correct, once the plane is back in the hangar, I put the dipstick back in. It's generally out for less than 10 minutes, but that's plenty of time to let the steam out.

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

  • edited March 2023

    Question: How is opening the oil dipstick on shutdown different than the crankcase breather line which is (or should be) always open? Do not both open the crankcase to the atmosphere?

  • MikeJJ:

    When the engine is running, there is a slight positive pressure in the crankcase (due to blow-by) that continuously "pushes" the hot air/vapor mixture out of the breather, and simultaneously replenishes it with more hot vapor. I suspect there is also be a venturi effect when flying, but I can't confirm.

    Even though the breather is open to the atmosphere, when the engine is shut down, the hot vapor becomes trapped because there is no longer a force pushing it out the breather tube.

    There is also a second force at work. Heat wants to rise. The breather opening is the lowest point (the belly), while the top of the dipstick tube is the highest opening. Anything above the lowest point is trapped and becomes stagnant because there is no escape path out the top where it wants to go. Opening the dipstick allows the hot vapor to escape from the crankcase through the highest point.

    Excellent question.

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

  • edited March 2023

    Excellent answer Griff. There are also other forces at work as the engine cools, long after you have closed the hangar door.

    I use to do a demo in my science classes to illustrate what happens when hot vapors are trapped in a sealed tin can, and then cooled. As the hot vapor in the can cools it contracts in volume and atmospheric pressure overcomes the falling pressure of the cooling vapor and literally crushes the can. I have even seen this done with a 55 gallon steel drum! Not that the engine will be crushed because it is not hermetically sealed, so there is always an exchange of pressure (and therefore flow) taking place between inside and outside of the engine as temperatures change.

    As the engine cools, the hot air in the crankcase will cool and contract in volume, and atmospheric pressure (and moisture) will enter through the breather, and any other way it can. As pressures equalize, which they will, the air inside the engine will exchange with the air outside the engine and will eventually have similar temperature, pressure, and, unfortunately, humidity.

    So, as Lycoming and Continental point out, a good way to improve the life of your engine is to fly it….often, and change the oil at 4 month intervals regardless of operating time.

    Reducing mechanical wear through approved oil additives like CamGuard, preheating when necessary, and looking after ignition components (plugs, wires, mags) will also give you an edge on engine life. If you are looking for a daily flying routine to extend the life of your engine how about this: go easy on those power changes and when you can, consider cruising at 65% power. Lycoming also thinks this is a good idea.

    pv=nRT 🤪


  • All great points Mike. I've seen the "crush the can without touching it" demo, and it is impressive.

    Yes, the 55 gal drum is even more impressive, and even if you're ready for it, most observers just about jump out of their shoes when it happens. On YouTube, there are videos of a railroad tank car being crushed in a similar manner to demonstrate what can happen if you pump the contents of the tank car out, and don't vent it to relieve the vacuum.

    PV=nRT isn't just a good idea, it's the law. 👍

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

  • To be totally accurate: PV=ZnRT

    PV = ZnRT, here Z is the compressibility factor for the given gas. The compressibility of a gas depends on the particular gas as well as temperature and pressure conditions. You can use different equations of state for calculating the compressibility factor of a gas as a function of temperature and pressure.

  • edited March 2023

    Roevadas and Mike; I think we're about to make everyone's eyes glass over. Let the glassing begin! 🤣🤣

    For non-ideal gasses, Roevadas is absolutely correct! Gosh, why would anyone want to use something that's not ideal? 🤣

    Pascal, Kelvin, and Avagadro have chimed in:

    Avagadro says never forget 6.022 x 10^23.

    Kelvin says never forget Tc=Tk + 273.

    Pascal says never forget 1 J/m^3 = 1 Pa.

    Gosh we're nerds 🤓

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

  • You guys are too much!

    I have an old shirt from the Kendall Square Coop that reads, "186,000 miles per second. It's not just a good idea, it's the LAW." It's been decades since that shirt would fit any of us. But it's now my son's favorite, and he went on his class trip to the Museum of Science this morning wearing it.

    I've never been so proud! : - )

    Bob Tingley

  • Bob:

    Classic shirt!! 👍👍

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

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