High Oil Temps revisited, Oil Types, etc.

[GAHorn]

I did some research lately into the high oil temps so many C145/O300 owners complain of. Here's what I've come up with.
Continental was opposed to external oil lines on their engines, and the "C"-series of engines was designed without them. Although an oil cooler design was produced by TCM (Continental Motors Corporation), Cessna was opposed to using it, probably for price considerations. So the C145/O300 installed in a Cessna runs hotter than the same engine in a Fairchild/Stinson/etc.. It also runs cooler in a Swift due to the updraft cooling.
Why would updraft cooling help? For one reason, the oil sump gets a nice first-chance at the cool air. But another major reason is because the pushrod tubes, being sheet-metal, and because the Cont. engines pump relatively high quantities of oil to the rocker boxes (much more than the Lycomings because of the better hydraulic lifters that Cont. uses) that subsequently runs back down those tubes to the sump, ...those pushrod tubes act as oil coolers and on the updraft cooling systems they also get a first-shot at the cooling air.
On a downdraft cooling system such as on our airplanes, the pushrods aren't in such a good position, as they sit downstream of those nice warm cylinders. Nonetheless, they still perform a function of cooling. And that's the problem.
If your exhaust flange gaskets leak, or if your exhaust riser clamps leak and spray hot exhaust onto your pushrods, a surprisingly large increase in oil temperature will result. So look for signs of exhaust blowing on your pushrod tubes.
There is not too many reasons for a 170 engine (C145/O300) to suddenly start running much hotter than 210-220 F. The most common reason for a sudden change is a faulty gauge. The next most common reason is a leaking exhaust flange. The third reason is faulty cooling baffles. The fourth reason is a broken or stuck piston ring, which can be detected with a compression test and subsequent blow-by into the crankcase.
Even a C145/O300 engine that has run all it's life with oil temps at or near redline will make TBO as often as other engines that run much cooler. The high oil temp does not seem to hurt the C145/O300 as much as it does some other engines. One reason for that is due to the location of the oil temp probe. Our oil temp probes are located at the oil inlet to the engine (at the oil screen.) Most other engines measure their oil temps at the outlet of the oil cooler. That's why they commonly indicate oil temps in the 180 degree range. Therefore it's not appropriate to compare the C145/O300 engine oil temp indications to other engines. If you'd measure the oil temps of most other engines at the inlet of their oil coolers their temp readings would be frightening.
So,...run SAE 50 wt oil in warm weather (above 40 degrees F) and SAE 30 in cooler weather (below 40 degrees F) order to take advantage of the higher 240 degree oil temp redline. (I've never seen SAE 30 aircraft oil, personally. Interestingly, SAE 40 oil is never approved for 240 degrees in our engines, apparently because it's not approved for use below 40 degrees F.)

[N1478D]

Better than GREAT information George!

What information is available for the correct position, attachment, materials, and locations for the cooling baffle seals? Are there pictures available that would show a good working installation of products that are available? The seals between the baffles and the cowls, and the seals where the leads enter the baffles, etc.

[Bill Venohr]

George--that is just the type of information we should know about our airplanes. I think it is a good point that George makes that comparison with other planes is not valid, however as we compare our 170s it certainly would be. During my recent annual I observed the blast tube was only partially oriented at the oil screen (filter for me) and so we moved it a little. That was worth at least 5 degrees drop in oil temp.

[Dave Clark]

Bill

What part of the oil filter and adapter did you aim for, the adapter, the filter itself, or a compromise?

[Bill Venohr]

I have the blast tube aiming at the area where the adapter for the oil filter comes out of the engine case. Basically, the same area where it hit with the screen. I think I recall some of the more recent oil filter adapter instructions specifically talked about redirecting the blast tube towards the filter itself. My tube was mostly blowing into the bottom portion of the cowling and that is why I moved it a little to direct it right onto the adapter.

[GAHorn]

Better than GREAT information George!

What information is available for the correct position, attachment, materials, and locations for the cooling baffle seals? Are there pictures available that would show a good working installation of products that are available? The seals between the baffles and the cowls, and the seals where the leads enter the baffles, etc.

The Illustrated Parts Catalog (IPC) illustrate the baffles (pgs 91/93 for the B-model, and the earlier models are also illustrated in their IPC's.)
The materials are sold by Spruce 877/477-7823, Univair 888/433-5433, and Wag Aero 800/558-6868. Get all those catalogs for your library.

[N1478D]

Better than GREAT information George!

What information is available for the correct position, attachment, materials, and locations for the cooling baffle seals? Are there pictures available that would show a good working installation of products that are available? The seals between the baffles and the cowls, and the seals where the leads enter the baffles, etc.

The Illustrated Parts Catalog (IPC) illustrate the baffles (pgs 91/93 for the B-model, and the earlier models are also illustrated in their IPC's.)
The materials are sold by Spruce 877/477-7823, Univair 888/433-5433, and Wag Aero 800/558-6868. Get all those catalogs for your library.

George, I have all of those. The Illustrated Parts Catalog (IPC) for the 170A shows the engine baffle on page 70. It does not show the baffle seals! A picture of a good installation of those seals and what was used would be very helpful.

[Dave Clark]

Bill

I had bought my plane with the blast tube pionting quite a bit forward and below the adapter, almost at the main case. I redirected it to the adapter housing and the temps came down, however I tightened up the bafles quite a bit at the same time so who knows?

The biggest fix I think was to put a strap from the center rear of the top baffle down to the center of the back vertical baffle to hold the top from blowing up under pressure. With the cowl off stick your hand in from the front all the way to the rear and lift up. You'll see what I mean.

[Bill Venohr]

I've noticed the gap there before and used RTV to seal it. Of course, you have to reseal every time the baffles comes off. Your way sounds better.

[lowNslow]

I did some research lately into the high oil temps so many C145/O300 owners complain of. Here's what I've come up with.
Continental was opposed to external oil lines on their engines, and the "C"-series of engines was designed without them. Although an oil cooler design was produced by TCM (Continental Motors Corporation), Cessna was opposed to using it, probably for price considerations. So the C145/O300 installed in a Cessna runs hotter than the same engine in a Fairchild/Stinson/etc.. It also runs cooler in a Swift due to the updraft cooling.
Why would updraft cooling help? For one reason, the oil sump gets a nice first-chance at the cool air. But another major reason is because the pushrod tubes, being sheet-metal, and because the Cont. engines pump relatively high quantities of oil to the rocker boxes (much more than the Lycomings because of the better hydraulic lifters that Cont. uses) that subsequently runs back down those tubes to the sump, ...those pushrod tubes act as oil coolers and on the updraft cooling systems they also get a first-shot at the cooling air.
On a downdraft cooling system such as on our airplanes, the pushrods aren't in such a good position, as they sit downstream of those nice warm cylinders. Nonetheless, they still perform a function of cooling. And that's the problem.
If your exhaust flange gaskets leak, or if your exhaust riser clamps leak and spray hot exhaust onto your pushrods, a surprisingly large increase in oil temperature will result. So look for signs of exhaust blowing on your pushrod tubes.
There is not too many reasons for a 170 engine (C145/O300) to suddenly start running much hotter than 210-220 F. The most common reason for a sudden change is a faulty gauge. The next most common reason is a leaking exhaust flange. The third reason is faulty cooling baffles. The fourth reason is a broken or stuck piston ring, which can be detected with a compression test and subsequent blow-by into the crankcase.
Even a C145/O300 engine that has run all it's life with oil temps at or near redline will make TBO as often as other engines that run much cooler. The high oil temp does not seem to hurt the C145/O300 as much as it does some other engines. One reason for that is due to the location of the oil temp probe. Our oil temp probes are located at the oil inlet to the engine (at the oil screen.) Most other engines measure their oil temps at the outlet of the oil cooler. That's why they commonly indicate oil temps in the 180 degree range. Therefore it's not appropriate to compare the C145/O300 engine oil temp indications to other engines. If you'd measure the oil temps of most other engines at the inlet of their oil coolers their temp readings would be frightening.
So,...run SAE 50 wt oil in warm weather (above 40 degrees F) and SAE 30 in cooler weather (below 40 degrees F) order to take advantage of the higher 240 degree oil temp redline. (I've never seen SAE 30 aircraft oil, personally. Interestingly, SAE 40 oil is never approved for 240 degrees in our engines, apparently because it's not approved for use below 40 degrees F.)

George, the C-145 manual list SAE 20 for below 40 degrees and SAE 40 above 40 degrees, or multi-viscosity. However, it mentions a "lubricant bulletin" of approved oils, do you know if this includes SAE 50?

[GAHorn]

Low'n'Slow wrote:
"George, the C-145 manual list SAE 20 for below 40 degrees and SAE 40 above 40 degrees, or multi-viscosity. However, it mentions a "lubricant bulletin" of approved oils, do you know if this includes SAE 50?"

SIL 99-2 is the service letter that specifies the sealants, lubricants, etc approved by Continental for the engines. You'll have to log onto their website and register under "Aviator Services" to get free access to Service Bulletins from TCM. http://www.tcmlink.com/

Basically, the approval basis for using 50 wt. oil is found in the C145/O300 Type Data Design Sheet, Note 1. It says that the maximum permissible oil temp is 240 deg. F when oil meeting specification MHS-24 is used, and that SAE 50 wt oil should be used above 40 F, and SAE 30 should be used below 40 F. (I've never seen SAE 30 wt in aviation oil, but it's doubtful you will have the need of an increase to 240 F redline in ambient temps below 40 F, so it becomes a moot point. Just use SAE 40 in winter. ) Multigrades do NOT allow an increase in oil temps.

Want the fast/simple answer? Use Aeroshell 100W in summer and 80W in winter.

[wa4jr]

Uhoh....I just picked up two cases of Aeroshell 15W50 today for an oilchange tomorrow. I run W100 in the summer, but was under the impression that 15W50 was the way to go in winter. Have I made a mistake here? W80 would sure be a lot cheaper...but then I think the synthetic blend 15W50 would be better for those cold starts. I tie down outside and there will be no preheat.

[zero.one.victor]

I use Phillips XC20-50 most of the year,in the middle of summer I use W100. The Phillips multigrade is much cheaper than the Aeroshell 15-50,not much more than W100. The Aeroshell multigrade is "semi-synthetic",if that does anything for you.
By the way,my engine overhauler recommended Phillips XC20-50,even for break-in.

Eric

[JDH]

I had been recommended 20-50 Mineral for break-in; 1st oil and filter change at 10 hours, then 25, than another 25. Once everything settled, Aeroshell 15W50. Last summer was very hot (for here) and I flew 25+ hours a month. After reading posts here, I tried Aeroshell W100 for summer use. I liked it; consumed less oil and temps-press. better. In the winter though, I put in 15W50. As a matter of fact, I changed oil and filters yesterday and went to 15W50, this morninng it is -3ºC and I put in my winter kit last week. Most people here use 15W50 in winter. Especially recommended if you do not fly regularly.
There is no reason not to pre-heat, even if you are nowhere near an outlet. I will be leaving for the airport in a few minutes and I will take digital pictures of a little system we use up here when we go winter camping; cheap and very effective, heat up in about 1/2 an hour at -15ºC.
Email me direct if you want me to send you a JPeg.
Sooo, I guess we all need to experiment and connsidering how muchh you fly, when and where you fly, temperatures, etc. Then, decide on what works best for you. JD

[GAHorn]

The over-boosted RAM engines we just installed on the C414 came with Phillips multi-grade Mineral oil in them, so that's what I broke them in with. The did so perfectly. After 25 hours the CHT's and Oil Temps fell in unison. We switched to AeroShell 100W and have run them for 40 hours now and not a single quart of oil has been added, ...they are still at 12 qts. (full)
I don't have a lot of faith in their methods, but Aviation Consumer just ran a series of tests on most of the common oils. Phillips failed the wear tests and the corrosion tests. (That might explain why it's OK to use it for break-in. ) Exxon Elite passed the (perhaps inappropriate) corrosion tests (barely) but failed the wear tests. AeroShell 15W50 passed both, and their Plus did almost as well. (But what AC didn't examine was the copper-leaching problems that Elite, AS-15W50, and Plus all have, and if you examine their testing methods, the process is questionable. Exxon replied that their (AC's) testing methods were "inconclusive", and AC themselves hedge their own bets with a disclaimer "any of the oils tested are suitable for use in aircraft engines." )
Engine oil and additives are the most hotly debated and most highly opinionated subjects imaginable. There's a "voo-doo" marketing logic to most of the product claims, and sometimes an owner will latch onto the marketing scheme purely out of hope that some magic elixir will make his engine "run smoother and stronger and cleaner, longer" than simple physical facts can allow.
I personally believe the best all-around oil is a good ashless dispersant straight-weight that can be easily found at all airports and in sufficient quantities that it can be purchased at discount, changed often, and flown frequently with a good spin-on filter. The multi-grade that AeroShell makes has a good reputation (for a multigrade) that is probably best in cold-starts. But don't forget that it also has a reputation of copper/zinc leaching, and of causing slipping troubles with starter clutches and starter angle-drives.