Summer oil temps. What to do?

[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.

 

[Infidel]

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]

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]

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]

Oil temps

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]

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

 

[flightlogic]

oil weight?

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]

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]

.... 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]

The Heat is on...

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

 

[DanH]

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.

Yes on the cooler size. As noted elsewhere, the systems has a positive displacement pump, so line size will change the pressure drop, not the volume. Heat transfer is all about mass flows.

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.

A large exit will improve cooling by increasing mass flow, up to the point where the fin passages become the system throttle. The inlet-exit ratio means nothing, zip, nada.

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.

Yep.

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.

Extra oil mass will decrease the rate of temperature change, but won't affect ultimate temperature.

 

[flightlogic]

wondering

Great input from all.... thanks Smokey, for the details.
Still have that original question though.... has harm been done?
220 degree flight let's say. Hour or two enroute in the summer. All other parameters that we all monitor electronically these days are nominal.
Have I done damage to my Lycoming? Or, is it just semantics....

 

[Ironflight]

Great input from all.... thanks Smokey, for the details.
Still have that original question though.... has harm been done?
220 degree flight let's say. Hour or two enroute in the summer. All other parameters that we all monitor electronically these days are nominal.
Have I done damage to my Lycoming? Or, is it just semantics....

Back when we escorted the RV-1 in to Oshkosh, we had one of every model RV in line - which meant we had to fly at the speed of a -12, minus some margin...so about 100 knots. It was as hot as it gets in Wisconsin in July. I was in the Val and watched as the oil temp creapt up due to lack of airflow - 220, 225, 230. It hit about 240 as I landed - then we got held to regroup as everyone cleared RWY 27. Then we PARADED down the 18 parallel to Aeroshell Square! I saw 256 before shutdown. Went straight to Allen Barret and asked what I should do. He siad to change the oil when I got home, and don't worry too much about it. Three years later, the engine is just fine.

I am not the ultimate engine authority, but I suspect you didn't do any damage at 220. YMMV.

 

[Randy]

Here I will share the result of some research regarding removal of the vernatherm if you should be so inclined. I am, since removing it is the only reasonable method I can think of to eliminate it as a possible cause or at least partial cause of my high oil temperatures. If I don't like the result I can always put it back in.

Be aware that I have not done this and flight tested it yet. I could have something wrong here but from my reading on this site and talking to folks with more knowledge than I, I believe what I write below is basically correct. If I have left anything out or got something wrong please correct me.

It is a pretty simple process. You can remove the guts of the vernatherm from the plug and reuse the plug without the vernatherm, or purchase a replacement plug. Install a new crush gasket and that part is taken care of. I did not record the crush gasket part numbers but the gal at ECI was able to look them up with no problems.

With the vernatherm gone, you can then install the Oil Cooler bypass spring, part # 69436, and the Oil Cooler Bypass plunger part # 62415. Those parts and some extra crush gaskets for them came to a little above $30.00 plus shipping from ECI. Beware that the plunger and spring should not be installed if the vernatherm is in place, they do not work together.

For some great photos and clarity of the install see post 14 from Dan H on this thread.
http://www.vansairforce.com/community/showthread.php?t=45548&highlight=vernatherm&page=2

When these parts are installed and the vernatherm removed, the engine has reverted back to the way they were many years back, with all of the oil being routed to the oil cooler all the time, unless the oil pressure should go way high, which would overcome the spring tension above the bypass plunger. Guestimate is about 100PSI required to bypass. The oil cooler and engine are still protected but you will not have thermostatic oil temp control unless you do so manually.

Larry Vetterman and others use a cable operated valve to control oil temps in the winter or I suppose any time they want higher oil temps. I already have a 4" butterfly valve on my duct work connected to a cable so I will try controlling oil temps in cooler weather by using that.

I feel this is a very safe procedure to try and Aerosport assured me that doing this will not void my warranty, and they ask me to report back my results.

It has also been stated that an oil cooler generally will not cool any better then 110F above the current ambient temperature. With that rule of thumb, and I suspect it is very close, on a 100F day, you are going to bust through 200F to about 210F. Perhaps I can live with that but I still want to keep under 200F to have some margin for those extreme situations like climbing out over the Sierra Nevada mountains from the floor of the valley in CA when the temps are over 100F.

I would be interested to learn if other people experience the same general result with oil temps about 110F above OAT. I suspect some will beat it to some degree and those are the setups I am wanting to learn more about.

It will be a week or so before I implement some changes, one at a time and measure results, then I will report back here.

 

[esco]

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?

Bottom Line: Yes.
If you overheat any oil (clues include lower pressure, darker color, burnt smell) protection against wear is reduced, causing lasting damage. That said, damage from overheating oil is generally slooowly additive, although it is cumulative (changing oil won't "unwear" a worn surface.)

In addition to the good advice on hot weather ops and equipment, suggest:
-Using an oil that you like;
-In the appropriate grade (Blackstone doesn't feel brands are significant);
-Monitoring symptoms; and
-Changing oil when it appears worn.

 

[rvsxer]

I install the plunger and spring in my O-360 every summer. You can leave the Vernitherm installed because the plunger causes all the oil to go through the cooler, negating the control benefit of the Vernitherm. A caution, however: on a lot of aftermarket oil filter adapters the Vernitherm and plunger assembly physically interfere with each other and can't be installed at the same time. Mine is a stock Lycoming adapter. I get an extra 10 degrees or so of extra cooling this way, checked over several seasons. The only reason I don't do something more permanent about oil temps (210-215F on a hot day) is because my engine has channel-chrome cylinders and suffers some blow-by, adding a direct heat load to the oil. A top or major overhaul will cure that. Dan Horton's thread on this has some excellent pictures so check that out.

 

[RV7Guy]

Over concern

Many get concerned if their oil temps hit 200 and their CHT's hit 400. This is not a big deal because they are usually transient temperatures. I live in the Phoenix area and used to fly my plane to work almost everyday. The hottest day I ever took off was 117 degrees. There is no possible way to keep the oil below 200 and the CHT below 400. Heck if that was the case we wouldn't be able to fly between May and October!!!

As Smokey noted, make sure the oil temp probe reads properly. Reduce the climb rate and reduce power some. Even in our hot temps when I flew to work at 3000' (1800 ft climb), as soon as I reached that altitude, I reduced power and the oil temp would drop to below 200 and the CHT would go down as well.

I changed oil every 25 and oil and filter every 50. Blackstone handled the analysis. In 800 hours there were no negative trends.

Go fly. Do your best to minimize the temps but certainly don't panic if you hit one of these numbers.

 

[flightlogic]

Darwin, thanks for the post. Currently with all the cops at Houston ALEA.... lots of A-Stars here. I have not really had any serious doubt that all would be ok. The tell tale signs given above, with smells, burnt oil, low pressure etc. don't really happen at 220F in my observation. I was opening the discussion to see if any of the really brainy guys here would bring up some data that was not in the
envelope of my smaller I.Q.
I have always thought oil was pretty low cost.... when compared with engine parts, and it gets changed pretty frequently. Samples always go down to PHX and no bad news in years.