Oil

I use 15/50 Shell oil. I’ve been doing that since I hung a valve in an O-300 in the eighties and was using Phillips oil. The good old boy who fixed my cylinder (I was on my way to SNF) told me I shouldn’t use that because they had all sorts of valve problems in their O-200’s (same cylinders) and they switched to Shell 15/5O. I did and no more problems. I’ve learned that since then Phillips did recognize a problem and changed their formulation and their 20/50 gets good reviews.

My new to me C170B which sat for 13 years and flew less than 5 hours a year for many years before that, has had two stuck exhaust valves in the first 15 hours of flying. The first was an away game so it was left for the local FBO to do a cylinder change caused by an ignorant repair shop, but not important now. The second one happened at my home field. This airplane has 250 SMOH but a lot of years. It has always used Shell 15/50.

After several consulting calls and measuring the valve springs from the cylinder that was replaced (which were out of spec weak) we decided to do the rope trick on all the others and clean the guides and replace the springs on intake and exhaust. It turned out that two cylinders had exhaust valves so tight they could not be moved by hand with the springs off. The rest of the cylinders were ok. The A&P working with me used to build engines for Mattituck and I have known him for years and respect his opinion. We cleaned the guides and stems and all good.

He tells me the Shell 15/50 is known to cause sticky valves and I should switch to 20/50 Phillips. So we have come full circle. I’m curious if anyone here has heard this. I know oil choices are very subjective sort of like guitar strings and bourbon, but I welcome opinions.

Rich

PS: I use MMO and TCP now, but of course have no idea what was done before.

In the past and perhaps still Cub Crafters has recommended Phillips 20-50 with a splash of Camgard in the 340. When I asked Aero Sport prior to taking delivery the tech was adamant that I use Aero Shell 100P after break which I've done. I do like the idea of an engineered package. On the other hand I think it might be a little like "holy water", you wouldn't walk by without putting a little on but you're not sure it really works.

I have used Phillips 20 W 50 for years with no problems. Because my 0 360 sits for an extended period I use cam guard with every oil change. A little MMO in the gas helps keep carbon deposits to a minimum.

I’ve used Aeroshell 15/50 in my O360 since I purchased my plane 13 years ago. Recently changed to Phillips 20/50. A local engine shop with a good reputation looked at cylinders brought in by a local mechanic that had significant pitting. They claimed that Shell changed formulation of 15/50 and since that change the shop had found pitting cylinders. They recommended Phillips 20/50. I never fact-checked the formulation change but did switch. Maybe others have more/factual information.

I have religiously used Phillips 20/50 plus Camguard in my Lycoming O-360, which never sat still for more than a couple of weeks. After 1800 hours, I had three stuck exhaust valves & then decided to get all four cylinders overhauled. Only 450 hours later, I had a stuck intake valve and a bent push rod (stuck exhaust valve). I can’t really complain, because the engine went past TBO, but five stuck valves seems odd. Phillips 20/50 plus Camguard was the only oil used in that engine once it was broken in.


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There was a good write up in AOPA (might have been EAA) magazine on stuck valves. What I got out of it was that valves stick because CHT’s are too low. The article went through the chemical reactions that occur and the temperatures required to achieve the desired reaction. Because Lycoming engines have sodium filled valves, the valves stay cooler. That makes it more difficult to get it warm enough to keep crap from building up.

I guess my engine is doomed to experience stuck valves because I can’t get it to run hot enough to satisfy the requirements in the article. Until reading that article I was always happy that high cylinder temps were never an issue, even on very hot days. No issues so far.............1400 on the tach.

I’ve had 5 other lycoming engines in various planes, a few of them that went past TBO, but never had a stuck valve on any of them.

The O-360 with all the stuck valves tended to run on the warm side. I was happy if it ran cylinder temps as low as 360 degrees.

Curious.......what oil did you run in the other engines?

My CHT’s typically run 320 - 330 in cruise, mid 360’s at full power climbing 90 mph.

One of the major issues with valves is 100LL has 5 times more lead than the engines where meant to run. DENNY

Maybe it is me but I find the fuel used plays a big part with valve issues. Engines designed for 80 Octane fuel do not play well when run on 100 Octane. To me Mo gas might be a better choice with the low compression engines.
Even the O360 with 8.5 compression is rated for 80 at least as far as the original data plate is stamped on the ones I have worked with.
MMO has allot of value but can not cure every buildup in the guides.

I read the article Mr. Ed refers to, damned if I can find it again. But with sodium pumping more heat out thru the stem, the stem is running hotter to keep the head cooler. We're talking about stems sticking, not the head. The stem should find it easier to support those chemical reactions. I think the article has it backwards, but I don't have it in front of me.

Mr. Ed said:

Curious.......what oil did you run in the other engines?

My CHT’s typically run 320 - 330 in cruise, mid 360’s at full power climbing 90 mph.

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Half of them ran Aeroshell 100, the other half ran Phillips 20/50.

Regardless of oil type try idling while leaned out at higher rpm for a bit before shutdown. Don't just land and quick kill the engine. Let the valve and cylinder temps cool down and stabilize clearances some. Might help reduce oil cooking in the valve guides. Valves loose heat through their lip to seat contact so open valves might remain warmer.

Gary

I think it was a recent article in AOPA by that Mike Bush character that claimed the deposits were not from oil and were from lead in the fuel and cool temps.

Gary brings up a good point. My cousin had an early Volvo turbo and would always idle it before shutdown. The plain bearing between the hot and cold sides of the turbo would coke up if the oil stopped moving. Some installed "turbo timers" so you could walk away from an idling Volvo.

I’ve owned my O-200 Cub for over 20 years, never a valve issue, never had a cylinder off. Ran a mix of Mogas and 100LL. 2 years ago I overhauled the engine, new Millenium cylinders. On my way home from AK last summer, noticed small stumble when reducing power (200 hours smoh). When I pulled the prop through, basically no compression in any cylinder with major leakage by the exhaust valves. Nurse it home, clean the guides and lap the valves. Large quantities of lead and/or carbon deposits on seats. Didn’t change anything from before overhaul except most fuel was 100LL. Respected local shop said he always checks the valve seats on new cylinders now as QC isn’t very good. If the problem comes back I’ll be pulling the cylinders and sending them to him. Very disappointing.

I believe that aircraft approved oils are all just fine. No scientific proof of that, but....

Example: University of North Dakota ran all their piston aircraft on Aeroshell 15 W 50, after initial break in. These airplanes are run regularly, but run by pilots with a VERY wide variety of knowledge and understanding of engine operations. While I flew their planes at least, we just didn't have valve problems that I ever heard of.

I ran several engines, both Continental and Lycoming, on Aeroshell 15-50, and never had problems. I also ran a few engines on Exxon Elite Oil, and some on Phillips 20 W 50 oil. I've run Camguard in all of these engines that I owned for years, and I believe that additive is well worth the price.

Primary problem I've seen is that some engines don't seem to like Shell 15-50, and they leak oil. I've been told by some mechanics that may suggest the engine wasn't properly broken in. I've broken in several engines and followed the engine manufacturers recommendations on this process. Never had an engine broken in properly leak oil.

Maybe I'm just lucky, but I just use good quality oils, and Camguard as the only additive. I would suggest that if you're having engine problems, it may not be oil related.....maybe.

MTV

I’m not looking to blame oil. This airplane sat for 13 years without the prop moving. As I said in the original post, all valve springs were changed because the first set we removed Were out of spec. Two exhaust valves were not moveable by hand once the springs were removed. Once the Carbon was removed things are running well so far with good leakdown numbers and no oil leaks.

My original question was posed because the mechanic who did the work was dead against using Shell 15/50 because “it sticks exhaust valves”. This is contrary to my 50 years experience owning eight airplanes, but as my old boss used to say: “Maybe he knows something we don’t know”. So I wanted to see what others have experienced. This being the place I go to get opinions based on experience. As you can see, the results are mixed. That COULD mean oil doesn’t matter.

Rich

mam90 said:

I’ve owned my O-200 Cub for over 20 years, never a valve issue, never had a cylinder off. Ran a mix of Mogas and 100LL. 2 years ago I overhauled the engine, new Millenium cylinders. On my way home from AK last summer, noticed small stumble when reducing power (200 hours smoh). When I pulled the prop through, basically no compression in any cylinder with major leakage by the exhaust valves. Nurse it home, clean the guides and lap the valves. Large quantities of lead and/or carbon deposits on seats. Didn’t change anything from before overhaul except most fuel was 100LL. Respected local shop said he always checks the valve seats on new cylinders now as QC isn’t very good. If the problem comes back I’ll be pulling the cylinders and sending them to him. Very disappointing.

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My brand new O-200 on my Legend Cub had two leaky exhaust valves in the first 200 hrs. Lead all over. Started using TCP and MMO and things got better. Still, once and a while one would stick for a moment. Maybe once every 50 hours. At least I think that’s what was going on. I sold it with 700 hrs on it with no other issues.

Rich

Oil may not matter as much as what's in it. Once suspended by the ashless dispersant things like carbon, build-up materials, wear metals, and combustion byproducts can move around and get stuck to surfaces. Surfaces like hot valves and guides, pistons (ring lands, skirts, and bottom inside), or the inside the valve covers on springs and things. The oil can leave behind whatever it was packing around so change it often. Filters help but only down to a certain size of material.

Gary

Brand? Multi weight or not? Makes no difference. https://www.blackstone-labs.com/wp-content/uploads/2018/09/Aug-17-AC.pdf

Like most things buy quality from a reputable company and the results are likely to be similar. For me it about the length of time the oil is protecting the guts while sitting idle.

Good article from Blackstone. I'm a believer in oil analysis.

Is is there a "Use by Date" for aviation oil? Would a case of oil that's been sitting on the shelf for a couple years be OK to use?

Jim

The main thing I see in that document is how very poor the ring seal is in these engines resulting in the high level of lead in each sample. I would love to see the numbers from engines run on Mogas.
I have seen the numbers from our race engines which have essentially no blowby. As in very little fuel contamination in the oil. These engines run fuels both with leaded gas and unleaded with octane ratings from standard pump gas to as high as 114 Oct.

I know you all know this but the best thing for an engine is to run it. I just sold an old O235C1 run out and the log book was interesting. It was installed in a Piper Colt in mid 1964. It received many 100 hour inspections but only one annual in it's total life of 1944TT over less than two years. Nothing was replaced, the entire engine went to TBO. 80/87 gas and ESSO oil was used.

Jack

Also note the increasing trend level of silicon in the O-300-D at the end of the article. That can come from intake dirt bypassing the filter and airbox heat flapper...while parked or when running. Might be worth a look at that part.

Gary

4400+ hrs on C85, 2 C90, 0200 and a Lyc 0145 and never a stuck valve. 99.99% of it burning mogas, 22,000 gals of it and every oil out there, Aeroshell mineral, 15 50, w100 and Phillips 20 50. Everyone who I flew with burning 100LL has had a stuck valve, some more then once. We had a friend here with a R680 Stearman who had a stuck valve a couple times a summer, switched to mogas and never had a stuck valve again



Glenn

cubdriver2 said:

4400+ hrs on C85, 2 C90, 0200 and a Lyc 0145 and never a stuck valve. 99.99% of it burning mogas,

Glenn

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Bingo

I would love to be able to buy corn free mogas. Unless some laws change down state NY will not be able to sell it. Mogas comes to the oil terminals on LI without alcohol. It’s mixed in there. After Sandy, we could not get gas for our cars. There was plenty of gas at the terminal, but the alcohol barge was stranded somewhere. In the few days it took to show up, the politicians had almost thrashed out an exemption but couldn’t quite get it through. Idiots. It would only take the stroke of a pen to get alcohol free mogas at the airports. Great alternative to 100LL for us low compression guys. Even the boat yards here have to sell gas with alcohol.

Conn is under the same requirement as you. I expect more areas around there than I have looked at. Makes it hard to have a hobby with boats or older cars since many aspects of them are damaged by the alcohol. In the summer I drive a 48 Yo car. All the rubber parts in the fuel system do not withstand the alcohol. The fuel pump diaphragm stiffens up and obviously it stops pumping.
This is no different with any mid 90s or older vehicle be it a boat or plane.
The rubber composition in aviation hoses will not withstand the alcohol.
Granted there are those that fly with E10 and say it works fine. Not with me onboard mate.

When I need to buy a jug load of E10, time permitting I pour a small amount of water in the jug and let it sit. The water draws the ethanol to the bottom. I then pour off the gasoline from the jug. Works best in the winter when the water/ alcohol turns into a slush-ice lump on the bottom.