Oil Temperature

[Frank DeBartolo]

I understand the the oil temp must get to 180 degrees F for the engine to displace moisture and must be flown for at least one hour for the moisture to "boil out" of the engine. I flew this afternoon and surface temp was 13 degrees C. I flew for 1.2 hours on the tach and the oil temps never got above 150 degrees F. If it is true that I need to properly operate the engine, at 180 degrees F--and if so, can I cover the little cooling vent at the front of the cowl that allows air to flow to the oil tank. Am I thinking right about this or is it much to do about nothing. My airplane is a 1946 BC12-D and the engine is an A65-8.

[PT13Pilot]

Re: Oil Temperature

Frank,
Anything you do will help in the cold. Blocking off the vent to the base of the engine and oil sump will help. I've also seen an oil sump blanket on a friends Champ, not sure where he got it. It also had wraps over the intake tubes. Basically little snap on heavy cloth covers as I recall. The little 65 has a hard time making and keeping enough heat when it's cold. An oil sump heater will help with starts and warmup if you have a hangar with electric too.
CJ

[Marv]

Re: Oil Temperature

I had a warming kit as you described in 1985. I got it from Wag-Aero. It worked realy well Marv

[VictorBravo]

Re: Oil Temperature

can I cover the little cooling vent at the front of the cowl that allows air to flow to the oil tank.

Yes, you can cover over quite a bit of the little square hole under the prop. My airplane flies with about 3/4 of it covered, even in warm weather, because I have low oil temps and high cylinder temps. (Blocking off the "oil opening" helps lower the ambient air pressure in the lower plenum chamber [under the cylinders] which in turn helps increase cooling flow through the cylinders.)

The square hole is actually not as much for flowing air onto the oil tank as it is for flowing air along the bottom of the engine crankcase. The lower crankcase is the primary oil return (drip) path to the tank and effectively a large sheet of aluminum for a radiator. Blowing air under the engine cools this large part of the case, which cools the sheet of oil as it drains down towards the oil tank.

If you want to run a super-quick experiment that takes all of about one minute, get yourself a roll of aluminum foil and wad up a bunch of it into the square opening, wedged under the engine. Leave a little room for air to flow through there but not a lot. Make sure the foil is wedged in so it cannot back out and get into the prop. Do a quick test flight around the pattern a couple of times to see if the oil temps come up.

If they do come up, then you can remove the aluminum foil and take the time to make a proper "winterization" cover for the square hole, using aluminum and P-K screws or Tinnerman nuts or whatever.

[PT13Pilot]

Re: Oil Temperature

Marv,
I looked, and Wag-Aero still sells them, $50 seems really reasonable. Also have one for the 6qt sump for $53.95.

Oil Tank Cover Kit, 4 & 5 Qt.
Model:
SKU: I-831-000

For most Cont. 65 thru 100 hp. Keep that engine warm! Easy to install. Quick snap on and off. Set of 4 induction sleeves included. Code 8

Oil Tank Cover Kit, 6 Qt.
Model:
SKU: I-832-000

For most Cont. 65 thru 100 hp. Keep that engine warm! Easy to install. Quick snap on and off. Set of 4 induction sleeves included. Code 8

[flyguy]

Re: Oil Temperature

I also use a plate that covers about 75% of that inlet. Produces both the effects that Bill is getting.

Even in our mild winters here I was only seeing 125F oil temperatures without the plate. Sugggest you could do a check using duck tape to hold a piece of aluminum over the entire opening. This is just for a test, but I think it will not even get overtemp on the oil, on an average flight, even with all the air blocked off. Of course that is with ambient temperatures below 60F or so at ground level.

Darryl

[VictorBravo]

Re: Oil Temperature

If I'm correct about the primary oil cooling coming from air flowing under the crankcase, then insulating the oil tank and the intake runners with those blankets will not do a whole lot for oil temps. The blanket would reduce the heat radiating out from the steel oil tank, but it would do nothing to prevent the heat radiating out of the large aluminum lower crankcase. My guess is that these little blankets were part of a larger winter kit, which included a cover for the cowl opening.

[Marv]

Re: Oil Temperature

Bill the kit i bought did not have anything but the sleeves and oil tank cover. I bought it new, and it worked realy well even givng me good heat in the cabin. Marv

[PT13Pilot]

Re: Oil Temperature

Yes, you definately need to cover the vent too, that's the biggest loss in heat retention right there. My customers Champ had the blanket things and the vent covered and the difference was substantial with both. I made a plate to cover the vent first, then he bought the covers. We didn't run it with just the covers, but both made a substantial difference in and of themselves.

[N95334]

Re: Oil Temperature

Ok, I think a little weird sometimes but to me the temperature being registered at the oil temp bulb is not the hottest the oil gets in the engine. Time it gets to the bulb it has cooled somewhat. Really this is a question because I don’t know anything. Seems to me, that any water in the oil will be vaporized when the oil is hitting those hot spots in the running engine that is above the temperature reading on the oil temp gauge. But then again I could be wrong and not allowed to interact with people.

[Frank DeBartolo]

Re: Oil Temperature

Tribe,

Thanks for the info. I will probably be having a plate made up to cover the the inlet. I will try 75% coverage to be on the safe side. I will let you know what happens.

Frank D
N43684

[flyguy]

Re: Oil Temperature

Pretty funny. Timing I mean. Went flying mid-day. Beautiful sunny day here. Two days ago I was up and oil temp had come down to to 150F climb/cruise. Today was Calif T shirt weather (that is warmer than say, Colorado T shirt weather, I think. LOL), and the oil temp just barely made it up to 125F on a 30 minute trip. Must be a bigger gradient between the ground and even 1500 feet up. Talk about sensitive to small temperature changes, wow. Darn thing needs cowl flaps.

Time, I think, to put on the little cover plate.

DC

[NY86]

Re: Oil Temperature

Ok, I think a little weird sometimes but to me the temperature being registered at the oil temp bulb is not the hottest the oil gets in the engine.

You are correct. The temp gauge reads the oil temperature as it enters the engine. This is a certification requirement, AFAIK. The point being that if it is too hot going in...

The 180 degree recommendation to boil off the water takes into consideration a 30+ degree increase as the oil goes through the engine, resulting in a maximum temperature high enough to boil water. If the max temp was 180 the water would boil off a lot slower than it accumulates.

[Frank DeBartolo]

Re: Oil Temperature

Thanks for the reply John,

I guess that if the temp is 150F at the gauge, then the highest temp in the engine is 180F and not hot enough to boil out the water. Do I understand this correctly? Also, I use Avblend. Could an additive like that help to maintain the engine if the temps do not get hot enough? Also how does viscosity affect the oil temp?

Frank D
N43684

[Hank Jarrett]

Re: Oil Temperature

There is a misconception that the oil has to be hot enough to boil the water out. It doesn't. It has to be hot enough to evaporate the water. I am pretty sure most of the water in the oil comes from condensation and not combustion (MOST) and a hot engine will evaporate the water out, just not as fast as one that the oil reaches 100C.
As for viscosity change due to temperature, the hotter the oil, the thinner (lower viscosity) it will get. The Society of Automotive Engineers (SAE) established the standard for viscosity at 100 and 0 degrees Celsius (212 and 32 degrees Fahrenheit, respectively). 10W40 oil will flow like a 10 at cold temperatures and a 40 at higher temperature. You get oils to do this by adding long chain polymers to the base oil that modify its characteristics (and believe me you don't want to listen to all the details).

Just to scratch the surface (which is what we really want to STOP with oils!) you need to know that "stokes" and "centistrokes" in the following are measurements of viscosity. The following is from the Valvoline tech sheets:

"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt.

"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt.

"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt.

"SAE 60 is SAE 60 no matter what the "W" prefix number is: 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 21.9 cSt and a maximum of 26.1 cSt.

"There is no SAE 70 and no one is likely to make one with a "W" prefix number although it is possible using synthetic base oil. This viscosity is identified as Grade 70. The viscosity @ 100 degrees C has a minimum of 26.1 cSt and no maximum."

The difference between a multigrade and a singlegrade oil: The singlegrade can't pass the low temperature viscosity test. If it did meet one of the following "W" viscosities, it would be a multigrade.

Go forth and be confused (but impress your friends!)

Hank
(Now you know why I'm an AERO Engineer, not a Petrolium Engineer)