my first flying summer has just began so my concerns about oil temperatures.
On my experimental lyco540 with 260HP, I've installed the same oil cooler as per Maule specs but the experimental high efficiency version.
Its fed by the original NACA scoop on the side of the cowling.

Say sea level OAT is 95F, on extended climbs I'm maxing 215-220F around top of climb. when reducing on cruise with around 18-20in of map and 2300rpm it cools down to around 205-210F. It's still within acceptable limits, but considering the high efficiency oil cooler I was hoping for something better.

For those around with a 235 or 260 installed with a NACA scoop, do you guys get similar values?


The oil sender has been checked with boiling water and is correct.

anyone?

What oil are you using?

I don't thintk that is a very high oil temperature for a climb. Water begains to boil at 212 F at sea level. You need to reach that temperature once in a while just to boil off the water you collect in your crank case from combustion or your going to make a lot of acidic sludge. I think your oil cooler is doing a great job.

You can extend the lip on the bottom of the cowling a little bit to increase the Venturi effect, that will draw more air through oil cooler as well as the cylinders.
Easiest way to test fit the additional length to the lip is HVAC aluminum tape over a piece of heavy poster board. I’d start out with poster board about 2”x what ever the length of the existing lip is and extend it down a 1/2” at a time and monitor the change and readjust in 1/2” increments until you get the results you want. Clean up the inside and out of the lip for the tape to stick well with your favorite degreaser ( mine is break cleaner) or it’s not gonna be there when you get back from the test flight

I’ve removed the fixed part of the outlet on the cowling and replaced with an adjustable cowflap which extends beyond the original. Cylinders temperature are doing very good I all phases of the flight. Was just concerned about the oil, but if these temps are normal then it’s all good. Thanks folks

Freedom you oil temps in my book are high. It’s not required to boil oil to get moisture out. 45 minutes of cruising at 180 degree temps will do just fine. Speaking of cruise, try running over sq at higher MP and lower RPM. Try 24/22 at 75 over peak. Should cool oil and cyl temps. Also 100 instead of multi velocity will normally bring oil temps down. You didn’t say anything about mixture but keeping it very rich on climb will also help on cyl temps first then oil temps. Les

I'm using 15W50. not running this high on purpose these temps are the best I can get on a climb. Crusie at altitude ten the temp cools down to an acceptable range. Cruise at low altitude in high temps the oil is jus at the edge. Cylinders temps are very good in every condition, climb, cruise high, cruise low. In climb I'm enriching the mixture thanks to the fadec.
Considering I've the stock NACA, same oil cooler as per Maule but the experimental high efficiency version which should cool every better.. that's why I'm concerned. Next summer will try switching to W100 see if it brings it down by 10F, that would already end in the acceptable range.

Hi Freedom , is the cowling air egress venturi lip the correct length and angle, and does it allow smooth flow including the short side pieces to achieve max venturi effect at egress.
Maule built the early 260hp versions with a 2" scat fresh air hose passing under the cylinders and above the intake tubes, which badly restricted down flow of air through cylinder fins. Is yours like that.
Is your engine top crossover baffling directing air correctly. Is your NACA scoop positioned so air flows cleanly from outside to front of oil cooler.
In cruise flight the original fiberglass top cowl can be seen deflecting downward as there should be more low pressure at rear of engine than ram air pressure from the front.