MooneyBob Posted February 11, 2014 Report Share Posted February 11, 2014 I went to see my baby today to make sure she is ok in this freezing temperatures. Routinely I have checked the oil level and it was lower about 0.25 qt. than I expected. I have checked the oil level after my last flight week ago as I always do. It was probably 1 hour after engine shut down but also outside temperature was in the 60 - ties. I don't know the oil temperature but I am estimating 80 F one hour after shutdown. Today it was 19 F in the hangar. So I have suspected it has something to do with the temperature. I have performed the volumetric cubic thermal expansion calculation and yes, it shows that my oil really did shrink in volume about 0.25 qt. Good to know. Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 12, 2014 Report Share Posted February 12, 2014 The challenge with the measurement and calculation is... (1) It takes a period of time for all the oil to run down into the pan. (2) It takes a longer period of time to cool to 19 deg. It is not hard to accidentally exceed the 'full line'. What value did you find for volume/degF of the oil? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Piloto Posted February 12, 2014 Report Share Posted February 12, 2014 Oil in cold weather takes longer to drain down to the oil pan. Even in the summer it takes about a week to drain down completely. José Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 12, 2014 Report Share Posted February 12, 2014 Hey! Where'd the snorkel coat go??? José you look like you changed seasons. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
MooneyBob Posted February 12, 2014 Author Report Share Posted February 12, 2014 The challenge with the measurement and calculation is... (1) It takes a period of time for all the oil to run down into the pan. (2) It takes a longer period of time to cool to 19 deg. It is not hard to accidentally exceed the 'full line'. What value did you find for volume/degF of the oil? Best regards, -a- I have used 0.00039 value for the oil expansion coefficient. I am trying to find out and record my oil comsumption very precisely as the plane is new to me and the engine didn't run too often last few years. So the question is when and how to check the oil level in order to find it out and eliminate the temperature volume change error. Maybe I am over complicating the issue. Thanks. Quote Link to comment Share on other sites More sharing options...
larryb Posted February 12, 2014 Report Share Posted February 12, 2014 So the oil shrinks in volume, but so does the oil pan. And what about the dip stick? Maybe your cold dipstick is just too short? I do think you are over-complicating this. My oil level is not constant. I rarely check the oil after a flight because it is always low. The oil hasn't drained back yet. It takes at least overnight for the oil to drain down. If I do check it before the 2nd flight of the day I take this into account. Sometimes it measures higher than the previous flight. It also depends on the type of flying. When I got the plane and did my transition training, with lots of takeoffs, I was getting maybe 4 or 5 hours/qt. In normal flying it's 7 or so hours/qt on avg. Sometimes 10, sometimes 5. Then when I did my instrument training, with all the approaches and climbs, the consumption went up again. You'll drive yourself batty trying to precisely measure the oil. I'm speaking from experience here... Quote Link to comment Share on other sites More sharing options...
carusoam Posted February 12, 2014 Report Share Posted February 12, 2014 The challenges of being a Mooney pilot... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Hank Posted February 12, 2014 Report Share Posted February 12, 2014 I have used 0.00039 value for the oil expansion coefficient. I am trying to find out and record my oil comsumption very precisely as the plane is new to me and the engine didn't run too often last few years. So the question is when and how to check the oil level in order to find it out and eliminate the temperature volume change error. Maybe I am over complicating the issue. Thanks. Yes, you are overcomplicating things. As mentioned above, consumption will vary with the type of flying you do, and draining back into the pan will also vary with flying type and temperature where parked. My old hangar was always above ambient in the summer and seemed to stay below ambient much of the winter. I check my oil just before pulling out of the hangar, and add half/whole quart when it gets below 5½ quarts. My target is 6 quarts, as anything over 6½ just ends up on the belly anyway. I keep a little notebook in the plane to record tach time, destination, etc., and I also record VOR checks, added oil and oil changes. Makes for simple recordkeeping, we are only talking about oil at $8/quart, not gold dust. Measurement will always be crude. Quote Link to comment Share on other sites More sharing options...
rbridges Posted February 13, 2014 Report Share Posted February 13, 2014 Maybe your cold dipstick is just too short? that's what my wife says to me all the time. 1 Quote Link to comment Share on other sites More sharing options...
Earl Posted February 13, 2014 Report Share Posted February 13, 2014 that's what my wife says to me all the time. I am fighting the urge to respond to this post........don't do it.........leave it alone......... Quote Link to comment Share on other sites More sharing options...
Hank Posted February 14, 2014 Report Share Posted February 14, 2014 Rob, tell her she needs to warm it up! Quote Link to comment Share on other sites More sharing options...
Bob - S50 Posted February 14, 2014 Report Share Posted February 14, 2014 I have used 0.00039 value for the oil expansion coefficient. I am trying to find out and record my oil comsumption very precisely as the plane is new to me and the engine didn't run too often last few years. So the question is when and how to check the oil level in order to find it out and eliminate the temperature volume change error. Maybe I am over complicating the issue. Thanks. Yes, you are overthinking it. However, if you want accurate readings (relatively speaking) just do it at the same time every time. That is, 15 minutes after shutdown, 30 minutes after, whatever works. You pick, but be consistent. Bob Quote Link to comment Share on other sites More sharing options...
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