Hi Zorg,
The accompanying text indicates that those figures in the generic TCM manual are for engine installations with an oil cooler. For typical installations with no cooler (C150 etc.) the green arc goes to 240 F (of course, modern synthetic oils can withstand much higher sump temperature). Unlike CHT, top of the green arc is good for engine longevity because it boils the water (a combustion product) and blows it out of the breather tube where it can’t rot the cam and followers.
Anyway, I really wouldn’t worry until you’ve changed to Total 15W-50 or similar ashless dispersant multigrade oil containing anti-wear and anti-corrosion additives. Opinions vary, but I can’t see any reason to delay that after bedding-in the piston rings. I’ve never known that to take more than about 10 hours.
Opinions vary about and synthetic and multigrade oil. Now that we have unleaded AVGAS it’s a toss-up between alleged corrosion and wear due to SAE 15 or 20 oil draining off steel parts if the engine is unused for long periods, and wear at each cold start with thick SAE 40 or 50 monograde oil. However I don’t think there’s any compelling evidence that the choice will significantly affect our overall cost of flying.
Jacko wrote:
On the contrary, that’s nicely in the range of 165 to 220 F recommended by Lycoming. Continental engines use the same oil and have a similar limit of about 245 F.
That’s not what I see in the Continental Operator’s Manual:
The normal range is stated as 150-170*F, so about 65-77*C. This is way lower than the values that I see, and the ones for Lycoming engines that you mentioned. 30-40*C higher oil temperatures seem like a big deal — or am I seeing this wrong?
Interestingly, my cylinder head temperatures are at the lower third of the normal range (300-420*F). I would’ve thought that high oil temperatures would coincide with high cylinder head temperatures.
Incidentally, after 40 hours it’s long past time to change to a decent ashless dispersant oil with anti-friction additives. That may reduce operating temperature a little. 100W and 20W50 have much the same viscosity at normal operating sump temperature.
I did an oil change with mineral oil (Total Aero 80) at 25 hours after top overhaul. At 50 hours since top overhaul, I will do another oil change, and replace with synthetic oil (Total Aero D80). As far as I understand, those are the Continental recommendations … right?
I often see 100-107 degrees Celsius at 2550 RPM, which is quite close to the limit stated in the Continental engine manual (125 degrees Celsius). That can’t be healthy, no?
On the contrary, that’s nicely in the range of 165 to 220 F recommended by Lycoming. Continental engines use the same oil and have a similar limit of about 245 F.
Incidentally, after 40 hours it’s long past time to change to a decent ashless dispersant oil with anti-friction additives. That may reduce operating temperature a little. 100W and 20W50 have much the same viscosity at normal operating sump temperature.
Zorg wrote:
Good idea, I will try to check oil temp. I don’t have a long mercury thermometer at hand — would a digital laser infrared thermometer like this one do, if I point it into the oil dipstick opening?The oil temperature display on the Dynon is quite jumpy — about 2-3 times per second, the temperature jumps by about 3-7 degrees Celsius. Does that seem normal?
Why not ,if this Laser tool gets fit with a long thin probe to pour it inside your dipstick hole.But before that,first check it into boiling water and see the readings.
Jerky indications,Yes I also had even with analog Westach instruments.Created by electromagnetic interference from the magnetos.I had to modify the cables routing.Then,indicators stayed quiet.
Another issue I thought: After OVH we have higher temps and consumption due to friction till things settle.Did you observe this elevated oil temp AFTER OVH ? If Yes,wait and see and DONT baby the engine.
Xtophe is half way to solving the calibration problem.
To check the sensor put it into a metal container and use a heat gun to heat the container and a reliable thermometer in the oil, ( or a laser thermometer ) this way you can test the indication system all the way up to the engine red line.
Can the oil temperature sensor be easily removed? Then dipping it in a mug of boiling water would give a good high temperature correlation point.
My first move would be to have the oil cooler ultrasonicly cleaned, if some of the galleries in the cooler are blocked it simply won’t work as well as it should……. or am I misunderstanding and you don’t curently have an oil cooler ?
These engines don’t usualy have problems with high temperatures, have you had any other problems like oil leaks from cylinder base seals or crank cases that have recently resolved ?
I’m not sure that I would get too worried about any temperatures that stay within limits as long as I was confident that the indication system was correct.
The thing that would trouble me would be low oil temperatures especially not getting above 180F during winter flying so you need to ask if fitting the after market cooler will over cool your engine in the winter ?
Zorg,
I can see your logic regarding the significant price of removing the surplus kit and the likely result.
You can easily check the oil temp/OAT correlation before engine start at the beginning of the day, to see if you get agreement at low temperatures.
The idea of dropping anything down the dipstick hole frightens me.
Stanley wrote:
My thought would be to get the mechanic to remove the surplus gear and see if it makes a difference. What is the downside apart from maybe 2hrs work?
I was quoted about EUR 500 for that work (including a replacement of the “propeller bolt” for about EUR 100 and about 6 hours of labour). The oil cooler would set me back about EUR 1’500 (including EUR 900 in parts). So my thinking was, the former might improve the oil temps, whereas the latter is almost certain to improve them. Or am I thinking wrong?
BTW, is it common for such engines to have no oil cooler?
MedFlyer wrote:
Before going for the oil cooler you may check the calibration of your Dynon sender right after landing by quickly comparing the indication with a very long mercury thermometer rated for say 150*C,tied with a thin fishing line which you will drop into your oil dipstick hole.Additionaly you may suspect broken piston oil ring if your consumption is high.Finaly you may convert to 100W ashless monograde.What about your oil pressure?Is the oil pump OK?
Good idea, I will try to check oil temp. I don’t have a long mercury thermometer at hand — would a digital laser infrared thermometer like this one do, if I point it into the oil dipstick opening?
The oil temperature display on the Dynon is quite jumpy — about 2-3 times per second, the temperature jumps by about 3-7 degrees Celsius. Does that seem normal?
I’ve had a top overhaul about 40 hours ago, and oil consumption is about 0.1 lph. So I’m currently still using mineral oil (Total Aero 80). I usually fill up to 3-3.5 quarts. (My dip stick has a min of 2 quarts, and a max of 4 quarts.) I will switch to synthetic oil in some 10 hours. Would that possibly improve oil temps?
Cylinder head temperatures (about 120-160*C) and exhaust gas temperatures (about 700-800*C) shown by my Dynon seem reasonable, no? Also indicated oil pressure is in the green (about 3 bars), albeit on the lower side of the green range.
