Oil

straight or multi weight oil which do you use

  • Straight weight

    Votes: 15 19.7%

  • Multi weight

    Votes: 61 80.3%
  • Total voters
    76
jesse said:
I doubt it'd be noticeable as to when you'd overhaul.
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True. As long as the engine hasn't been abused, just about any oil will get you to tbo and beyond. Can't say using X oil will add another 200 hours of life. But after you've seen enough taken apart, it's easy to tell what oil was used without opening the logbook.
 
Multi in winter. Single in summer if I get the timing right and need an oil change before about July 1. I've noticed that in hot weather, I have to add multi-vis oil more often than I do when running single weight.
 
I used straight-weight oils in my old A-65. Then I put Aeroshell 15W50 in it, and saw the oil temps drop by as much as 30 degrees. That oil has the Lycoming anti-friction additive in it. When oil temps drop like that, it means there is less friction, and less friction means less wear.

We ran the flight school airplanes on that 15W50, and all reached TBO with the compressions still in the high 70s and the oil pressures still high. No metal in the filters, either, other than in the O-235, which has famous issues with running too cool and suffering crankcase condensation as a result, which pits the cylinders, letting the rings wear them down and leaving a ridge at the bottom of the ring travel that shaves the aluminum piston pin plugs. Maybe that engine would have done better on a straight-weight, running hotter and driving off the moisture.

A multigrade is a light oil with viscosity modifiers that clump together when hot to thicken the oil. It's a good invention.

This is the general idea:

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tyndall said:
True. As long as the engine hasn't been abused, just about any oil will get you to tbo and beyond. Can't say using X oil will add another 200 hours of life. But after you've seen enough taken apart, it's easy to tell what oil was used without opening the logbook.
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Please share more.
Thank you.
 
jesse said:
That is a lot of work, lol...Also nothing like waiting for oil thicker than molasses to drain out of an airplane while you're freezing your ass off. I would use an electric block heater, and if that weren't available, a propane powered solution.
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No, you drain it the day before, when it's still warm from flying.
 
Whitney said:
Yes.

I should have added that in cold weather we drain the oil after landing.
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Lol...you drain the oil every time you finish flying as a regular practice? Certainly you could come up with a better option. I grew up and learned to fly in Minnesota. Our winters were not warm. Draining oil then heating that oil up was something that was certainly heard of, but definitely considered a last resort option. Works better to plan in advance and just have what you need to pre-heat available before you shut down an engine for an extended period of time there. Where power is available, plugging in a cheap electric block heater is a hell of a lot better option. Alternatively, where it is not, propane works well.
 
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In my itty bitty airplane, the oil was changed about every other landing, so it didn't matter.

I've got to remember to replace that oil cap seal...
 
I spend many winters in Mexico, where its warm.
But come winter time if still in BC or the Yukon, and its forecast to be more than -25C for the next while, I do drain it if there is a reasonable chance I'll be going flying, before temps warm up again.
If above -25C i have 4 electric heaters I use, 2 for the engine, and 2 for the interior.
But for those really cold days, there is nothing like nice warm oil for an easy start.
Draining the oil out 4 or 5 or so times a winter is no big deal.
 
Just a bit of aircraft engine trivia: On some radial engines gasoline is injected into the oil sump to thin the oil for cold starting. The gas added to the oil evaporates as the oil warms up. I believe the P&W R-2800 Double Wasp used this feature to thin the oil for startup.
 
I use a candy thermometer to make sure I don't over heat the oil.
Around 90 to 95 C is good, then pour it into the engine.
Wait 5 minutes for it to warm the engine up some, and start it up.
 
Whitney said:
I use a candy thermometer to make sure I don't over heat the oil.
Around 90 to 95 C is good, then pour it into the engine.
Wait 5 minutes for it to warm the engine up some, and start it up.
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First it was the skillet and now it's the candy thermometer ... ;)
 
I have a dedicated double boiler, and candy thermometer, that is used exclusively for heating up my engine oil.
 
Brad Smith said:
Just a bit of aircraft engine trivia: On some radial engines gasoline is injected into the oil sump to thin the oil for cold starting. The gas added to the oil evaporates as the oil warms up. I believe the P&W R-2800 Double Wasp used this feature to thin the oil for startup.
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Not just radials. Even the Cessna 180/185 had it.
 
When I was living north of the Arctic Circle, we had engine blankets to wrap around the cowling(s), cowl plugs and tanis heaters on the engine(s). Also another electric heater under the instruments and still the gyros would howl like a banshee after start up. By company op specs we were no allowed to start a piston engine under -40. whether that was -40f or c didn't matter...'cause that is freaken' cold, which is not the last level of cold. The last level of cold is scary cold. That means it is so cold you do not care what you look like with all the arctic clothes you are wearing because you are finally almost warm. I hated it when the eyelids would freeze closed during a blink. A good pair of ski googles would solve that problem. If stuck in a village and not able to plug in, I have stayed with the plane to crank it every 15-30 minutes to run it up to operating temps.

But with all the heat added to the engines the oil would drip off the dipstick and they would start easier than in summer when they had no overnight heat at all. Scary part was the howling gyros and the frozen oil in the lines going to the oil pressure gauges, scary because it would take a few minutes before the oil pressure would come off 0.

I have driven through BC and Yukon a few times, but I have never flown that far south. (not counting the air ambulance in New Mexico and Kansas) I flew out of Juneau one summer and that was pretty lame. (sorry AkBill :lol:) I guess when I wanted to go north, I meant north.!!
 
Zeldman said:
When I was living north of the Arctic Circle, we had engine blankets to wrap around the cowling(s), cowl plugs and tanis heaters on the engine(s). Also another electric heater under the instruments and still the gyros would howl like a banshee after start up. By company op specs we were no allowed to start a piston engine under -40. whether that was -40f or c didn't matter...'cause that is freaken' cold, which is not the last level of cold. The last level of cold is scary cold. That means it is so cold you do not care what you look like with all the arctic clothes you are wearing because you are finally almost warm. I hated it when the eyelids would freeze closed during a blink. A good pair of ski googles would solve that problem. If stuck in a village and not able to plug in, I have stayed with the plane to crank it every 15-30 minutes to run it up to operating temps.

But with all the heat added to the engines the oil would drip off the dipstick and they would start easier than in summer when they had no overnight heat at all. Scary part was the howling gyros and the frozen oil in the lines going to the oil pressure gauges, scary because it would take a few minutes before the oil pressure would come off 0.

I have driven through BC and Yukon a few times, but I have never flown that far south. (not counting the air ambulance in New Mexico and Kansas) I flew out of Juneau one summer and that was pretty lame. (sorry AkBill :lol:) I guess when I wanted to go north, I meant north.!!
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We don't get below -40 here, but I have seen plenty of -50 when in the Yukon where I used to live.
When its cold out, I bring the propane tiger torches inside to keep them warm, then take them out and light them, and use under the tractors and semis some mornings, despite the block heaters being plugged in. Helps warm them up, especially the oil.

And I think all plane owners have cowl covers up north, plus add several blankets on top of that. I find interior heaters are a must, for all the instruments in my plane.
Thankfully my car and truck are parked in a heated garage.
I've talked about building a real hangar, with heat, for 15 years, really should have done so.
My plane sits in an old barn, with modified doors, to get the width needed for the wings. It has a dirt floor, no heat, but keeps some of the weather from beating up the bird so badly.
 
Whitney said:
Please share more.
Thank you.
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An engine that’s made it to tbo on xc 20/50 will usually look as expected - dirty, maybe a bit of corrosion, but overall good shape. One that’s had a life of W100 will usually be varnished up. That’s not a bad thing as the coating has saved more than a few that were sitting way too long. If it’s been on 15/50, it’s time to break out the big hammers to get it apart. Stuck rings and piston pins, and looks like someone left it outside in a dust storm. But it’s somewhat of a necessity when it gets stupidly cold. All of this is accumulative, so you’d have a hard time seeing a difference at mid time. As I said, any of them will get you to tbo.

Just a bit of anecdotal data from a hundred or so engines. FWIW, I’m a straight weight guy from up north. If it’s too cold for the oil, it’s probably too cold for me to pull it out of the hangar.
 
tyndall said:
An engine that’s made it to tbo on xc 20/50 will usually look as expected - dirty, maybe a bit of corrosion, but overall good shape. One that’s had a life of W100 will usually be varnished up. That’s not a bad thing as the coating has saved more than a few that were sitting way too long. If it’s been on 15/50, it’s time to break out the big hammers to get it apart. Stuck rings and piston pins, and looks like someone left it outside in a dust storm. But it’s somewhat of a necessity when it gets stupidly cold. All of this is accumulative, so you’d have a hard time seeing a difference at mid time. As I said, any of them will get you to tbo.

Just a bit of anecdotal data from a hundred or so engines. FWIW, I’m a straight weight guy from up north. If it’s too cold for the oil, it’s probably too cold for me to pull it out of the hangar.
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Thank you!
 
tyndall said:
An engine that’s made it to tbo on xc 20/50 will usually look as expected - dirty, maybe a bit of corrosion, but overall good shape. One that’s had a life of W100 will usually be varnished up. That’s not a bad thing as the coating has saved more than a few that were sitting way too long. If it’s been on 15/50, it’s time to break out the big hammers to get it apart. Stuck rings and piston pins, and looks like someone left it outside in a dust storm. But it’s somewhat of a necessity when it gets stupidly cold. All of this is accumulative, so you’d have a hard time seeing a difference at mid time. As I said, any of them will get you to tbo.
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I’ve noticed the same trends in the engines I’ve overhauled.

tyndall said:
Just a bit of anecdotal data from a hundred or so engines. FWIW, I’m a straight weight guy from up north. If it’s too cold for the oil, it’s probably too cold for me to pull it out of the hangar.
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A mentor and former boss of mine had the opinion that multi viscosity oil was one of the worst things that happened to aviation because it allowed engines to start in weather that is colder than they should be running in without taking the proper precautions. As the years go by, the more correct I think he was.
 
On the gopher engine I'd switch from 50 to 40 based on the season. Now I just run FlyLips 20W50 year round.
 
Dan Thomas said:
I put Aeroshell 15W50 in it, and saw the oil temps drop by as much as 30 degrees. That oil has the Lycoming anti-friction additive in it. When oil temps drop like that, it means there is less friction, and less friction means less wear.
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Lycoming's TPP additive is an anti-scuff additive, not an anti-friction additive. It's likely that your engine ran cooler on AeroShell 15W50 because the synthetic lubricant (50% of the blend) did a better job of reducing friction, and a better job of transferring heat in your oil cooler.

Paul
 
PaulMillner said:
Lycoming's TPP additive is an anti-scuff additive, not an anti-friction additive. It's likely that your engine ran cooler on AeroShell 15W50 because the synthetic lubricant (50% of the blend) did a better job of reducing friction, and a better job of transferring heat in your oil cooler.

Paul
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Are scuffs not friction? I have the same misconception about what the anti-scuff additive is actually doing in those 76 series engines then, if not reducing friction. Eager to learn :)
 
It may reduce friction, but the purpose of the Lycoming additive is to reduce corrosion related wear on the sliding surfaces.
 
Brad Smith said:
Just a bit of aircraft engine trivia: On some radial engines gasoline is injected into the oil sump to thin the oil for cold starting. The gas added to the oil evaporates as the oil warms up. I believe the P&W R-2800 Double Wasp used this feature to thin the oil for startup.
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It’s called oil dilution and most of the WWII airplanes had it, although I have not seen any today with it still installed.
 
Dana said:
It may reduce friction, but the purpose of the Lycoming additive is to reduce corrosion related wear on the sliding surfaces.
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I guess that makes sense. Lycoming cams are above the engine. Continental are below, bathed in more oil. Did I get that right?
 
Sac Arrow said:
I guess that makes sense. Lycoming cams are above the engine. Continental are below, bathed in more oil. Did I get that right?
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Typically it's the cowling that's above and below the engine. Cams are usually above or below the crankshaft. ;)
 
tyndall said:
Typically it's the cowling that's above and below the engine. Cams are usually above or below the crankshaft. ;)
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Oh. Right. You got some relish handy for my hot dog? Maybe some (please don't say ketchup)
 
schmookeeg said:
Are scuffs not friction? I have the same misconception about what the anti-scuff additive is actually doing in those 76 series engines then, if not reducing friction. Eager to learn :)
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Scuffing is the wearing away of a surface by mechanical rubbing. TPP forms an iron-phosphate layer on the metal surface of the lifter body, so that as the cam lobe rubs against the surface, the underlying metal is not scuffed away.
Friction is the conversion of mechanical energy to heat by the rubbing of two surfaces. There's no data that suggests lobe against steel lifter body generates more heat than lobe against iron-phosphate coated lifter body. In fact, the iron-phosphate anti-scuffing layer does wear away, and then reforms by new reaction. That might generate more heat than the original condition. But, it does prevent wearing away of the lifter body face.

Paul
 
Whitney said:
Anti scuff=anti friction.
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Friction consumes an amazing percentage of the power output of our engines... something over 10%. What mechanism do you have in mind that a phosphate layer would reduce that power being turned into heat loss?

Paul
 
PaulMillner said:
Scuffing is the wearing away of a surface by mechanical rubbing. TPP forms an iron-phosphate layer on the metal surface of the lifter body, so that as the cam lobe rubs against the surface, the underlying metal is not scuffed away.
Friction is the conversion of mechanical energy to heat by the rubbing of two surfaces. There's no data that suggests lobe against steel lifter body generates more heat than lobe against iron-phosphate coated lifter body. In fact, the iron-phosphate anti-scuffing layer does wear away, and then reforms by new reaction. That might generate more heat than the original condition. But, it does prevent wearing away of the lifter body face.

Paul
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Thanks! I always enjoy your posts on the ins and outs of petrochemical lore when I encounter them. :D
 
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