Summer oil temps. What to do?

flightlogic · #1 07-15-2015, 08:44 PM

I see a common theme each summer with RV's. Oil temps get up near the limit, but pilots mitigate and keep them in line. We are solution driven, and I see many mods and ideas to "cure" the issue. Nothing very straight forward seems to emerge though.
But, my question is: Is there really harm done? If we run a heavy weight oil, stay below redline, maybe shorten the interval in summer between oil changes and step climb..... have we done any lasting damage?
If pressures are good and filters are cut.... samples sent for analysis possibly, can we just carry on and cooler temps will be along soon?
Any and all thoughts welcome.

Infidel · #2 07-15-2015, 10:20 PM

My oil temps never get close to the limit. But then again, Prescott Az is a bit different. On an +80*f day, I can close my oil cooler shudder and manage to reach 180*f. It's the colder months that causes me concern and more rampant oil changes.

Far North Texan · #3 07-15-2015, 10:41 PM

My RV-6A never seems to run too warm. I use Shell 15W-50.

I used to have a Cherokee 235. With it, using W-80 in the summer, it would show oil temp well into the yellow. changing to 15W-50 lowered the temps to the green area of the gauge even on the hottest days. You may try that if you are using single weight oil. It made a big difference in that plane anyway.

Randy · #4 07-16-2015, 04:08 AM

I just had a conversation with Doug at Aeroeport about my oil temps. I have tried to keep them below the 200F mark but flying in the California Valley with OATs above 100F it is nearly impossible.

I am studying the issue in depth and will do some measuring of pressure delta across the cooler to see if that might be related to the cause. I did learn that my engine has oil squirters so that explains some of the problem.

I have IO-375, low compression, with dual P mags, now at 75 hrs. Reducing the timing via offsetting 2.8 degrees did not help temps. Need to think about creating my own timing curve I guess. In cruise at 9500' I see 32 deg advance (using EIC). It was a little under 34 deg before the adjustments.

Any way, more related to OP, in my conversation with Doug at Aerosport he encouraged me to keep the oil temps down with maybe a 215F redline, but did quote the Lyc. 245F limit. Advice from Pacific oil coolers was that I am being too conservative on oil temps and not to worry till 235F.

So the opinions on this one are all over the place. Maybe I need to get some more and average them?

Once I find a way to improve my setup I will report back. I may end up eliminating the vernatherm to keep oil to the cooler at all times and eliminate the possibility of too much oil bypassing the cooler. Then again, I may need more pressure delta to get improvement, only measurement will tell... My exit area on A model is untouched but running EZ cool cowl flaps, they help for sure but do not solve the problem in my case. Maybe I need to do some cutting to open up some more exit area but hate to go that route. I was hoping to be able to shrink the exit at some point...

texdog · #5 07-16-2015, 04:56 AM

What oil are you using? I have had high oil temps using multi-grade. I go back to Aeroshell 100W and the problem goes away with less consumption. This has happened on many different engins.

RV Jerry · #6 07-16-2015, 08:52 AM

I agree multi vis oils have increased my temps, aeroshell100 plus works best for me

flightlogic · #7 07-16-2015, 09:38 AM

Intuition told me that heavy, single grade might be best, but we have had reports know... of both results. I hope more posters input their experiences and I hope some engine rebuilders or metalurgists lurking in our membership will come forward.

RVDan · #8 07-16-2015, 10:14 AM

I have been running the Mobil 15-50W multivis and am also experiencing high oil temps. Along with that when the oil temps are over 200 F the oil pressure starts getting a bit low at about 60PSI. Oil burn also increased. I have been thinking about going back to 50-100 AD oil also.

PerfTech · #9 07-16-2015, 10:36 AM

.... We service and do installations of our products on a lot of Rvs. The one common issue we see all the time with carbed 320's is "TOO LEAN". This will cause or contribute to temperature problems and should be verified. Should you need help or have a question please feel free to give us a call.
.... You my want to have a look at our EZ-Cool Cowl flaps as well and review the video on our website. Thanks, Allan...

smokyray · #10 07-16-2015, 10:51 AM

Quote:

Originally Posted by flightlogic

I see a common theme each summer with RV's. Oil temps get up near the limit, but pilots mitigate and keep them in line. We are solution driven, and I see many mods and ideas to "cure" the issue. Nothing very straight forward seems to emerge though.
But, my question is: Is there really harm done? If we run a heavy weight oil, stay below redline, maybe shorten the interval in summer between oil changes and step climb..... have we done any lasting damage?
If pressures are good and filters are cut.... samples sent for analysis possibly, can we just carry on and cooler temps will be along soon?
Any and all thoughts welcome.

Hi Nick!
After 25 years of RV-8ing this is what one would call a "standard" issue.
So, what are things I have done to solve theses issues since 90% of my RV/Rocket flying (as you well know) has been in hot/humid climates?
You have to first examine the design, a closely cowled, low drag airframe and engine almost begs higher temps at low airspeed and altitude. So...how to fix the problem? Make sure your temp probe is accurate by removing it next oil change, boil some water and carefully dip the sender in the boiling water. Should read 212. Now you have a baseline.

1. Largest Oil cooler available. If your 0-320 calls for a 7 row, install a 9. 0-360? install an IO-360 cooler. Sounds basic but has solved the problem countless times for myself and customers. Also install #8 lines vs #6.

2. Make sure you have a 1:1.5 ratio of inlet to outlet air through your cowl. Measure the inlets area and the outlet. Outlet should be 1.5 versus the 1.0 for the inlet. Remember, the RV exhaust pipes use up valuable exit air space.
Works, trust me.

3. Change your flying habits. Takeoff and climb at shallower angles, cruise climb at 120-140 and fly at higher altitudes (above 5K), lower power settings.

4. Leave oil service door open on ground. Limit taxi time and keep your oil level at a higher level than normal (8 vs 6) but not over max as it will throw it overboard.

Hopefully one or all of these you have tried, helps!
V/R
Smokey