Preheat Engine With Hot Oil

[AlanA]

To help raise the oil temp on a cold morning I have experimented with adding hot oil into the crankcase. I set a bottle of oil in a pot of boiling water until it is very hot. Then I pour the heated oil into a thermos and take it with me to the airport and add it to the plane. I normally run the plane on 6 1/2 qrts to 7 qrts so there is plenty of room for another quart. I also have an external engine heater. My thought is that using both methods I am heating both the inside and outside at the same time. I haven't timed it but at the very least I feel that it speeds up the process.

Has anyone else tried this? Do you think there could be any harmful effects from this?

[M016576]

I wouldn't think it would harm anything, but it won't do any good. The primary reason for a pre-heater is to heat the cylinders and case to a "normal" temp prior to start to prevent excess metal wear. The oil is a helpful side effect but not the primary focus of preheating....,

[N201MKTurbo]

I believe there are a few issues with starting a cold engine. One is frosting the spark plugs which happens when spark plugs are below freezing. The pressure drop from the piston sucking the air into the cylinder can cause the temperature of the intake charge to drop below the dew point and the liquid water can freeze on the electrodes shorting the plug.

Almost everything else is caused by cold oil.

The oil can get so viscous that the starter cannot turn the engine fast enough to start.

Once the engine starts the oil is so viscous that it does not flow in the engine, starving the bearings of oil.

The parts at most risk when starting a cold engine are the cam lobes and piston pins. These parts rely on splash lubrication (or oil jets) and until the oil is flowing freely they are starved of oil.

I think the worst thing you can do is cold start an engine that has been sitting for a long time so the oil has drained off the cam and lifters.

If I could not heat the whole engine, I think heating the oil would be a good choice.

Also make sure you change to multi-weight oil if you are planning on flying in cold weather.

I believe there are a few issues with starting a cold engine. One is frosting the spark plugs which happens when spark plugs are below freezing. The pressure drop from the piston sucking the air into the cylinder can cause the temperature of the intake charge to drop below the dew point and the liquid water can freeze on the electrodes shorting the plug.

Almost everything else is caused by cold oil.

The oil can get so viscous that the starter cannot turn the engine fast enough to start.

Once the engine starts the oil is so viscous that it does not flow in the engine, starving the bearings of oil.

The parts at most risk when starting a cold engine are the cam lobes and piston pins. These parts rely on splash lubrication (or oil jets) and until the oil is flowing freely they are starved of oil.

I think the worst thing you can do is cold start an engine that has been sitting for a long time so the oil has drained off the cam and lifters.

If I could not heat the whole engine, I think heating the oil would be a good choice.

Also make sure you change to multi-weight oil if you are planning on flying in cold weather.

[N201MKTurbo]

Wow, my computer is going crazy! Major cut anf paste error!

[Alan Fox]

I believe there are a few issues with starting a cold engine. One is frosting the spark plugs which happens when spark plugs are below freezing. The pressure drop from the piston sucking the air into the cylinder can cause the temperature of the intake charge to drop below the dew point and the liquid water can freeze on the electrodes shorting the plug.

Almost everything else is caused by cold oil.

The oil can get so viscous that the starter cannot turn the engine fast enough to start.

Once the engine starts the oil is so viscous that it does not flow in the engine, starving the bearings of oil.

The parts at most risk when starting a cold engine are the cam lobes and piston pins. These parts rely on splash lubrication (or oil jets) and until the oil is flowing freely they are starved of oil.

I think the worst thing you can do is cold start an engine that has been sitting for a long time so the oil has drained off the cam and lifters.

If I could not heat the whole engine, I think heating the oil would be a good choice.

Also make sure you change to multi-weight oil if you are planning on flying in cold weather.

I believe there are a few issues with starting a cold engine. One is frosting the spark plugs which happens when spark plugs are below freezing. The pressure drop from the piston sucking the air into the cylinder can cause the temperature of the intake charge to drop below the dew point and the liquid water can freeze on the electrodes shorting the plug.

Almost everything else is caused by cold oil.

The oil can get so viscous that the starter cannot turn the engine fast enough to start.

Once the engine starts the oil is so viscous that it does not flow in the engine, starving the bearings of oil.

The parts at most risk when starting a cold engine are the cam lobes and piston pins. These parts rely on splash lubrication (or oil jets) and until the oil is flowing freely they are starved of oil.

I think the worst thing you can do is cold start an engine that has been sitting for a long time so the oil has drained off the cam and lifters.

If I could not heat the whole engine, I think heating the oil would be a good choice.

Also make sure you change to multi-weight oil if you are planning on flying in cold weather.

Have to disagree completely , The colder the oil , the greater the film strength ... The oil will lubricate ... If the oil gets so viscous that the starter cant turn the engine , The battery probably wont start it either ...If the oil wont flow , the pump will hydrolock and break... I have never heard of this .... Bottom line ... Preheat for as long as it takes to get the engine up to 40 degrees...

[scottfromiowa]

This is a classic case of..."If you don't know, DON'T TELL"...

[jetdriven]

Muiltigrade oil is thin at cold temperatures, and will eliminate many of the cold starting concerns. Philips X/C oil was introduced in 1976, just sayin'

[N201MKTurbo]

If the oil won't flow it goes out the pressure regulator.

It goes from the pump to the filter which has a pressure bypass to the cooler (after the vernatherm closes) and then to the regulator. Those are all large passageways. After the regulator it goes to all the small openings.

I have to confess my sins...

I flew my M20F for about 2500 hours out of Denver. I have started the engine from stone cold at -20F. I flew almost daily for six years. The only time I preheated the engine is when I couldn't start it. I did this because I was in my 20s and didn't want to spend the money if I didn't have to. I was involved in both overhauls of the engine during this time and there was no indication of any damage from my cold starts.

Pre heating the engine certinly makes it easier to start, there were times when only one cylinder would fire, it would pop like a one lung farm engine until another cylinder would fire. I'm not recomending that anyone operate their engine this way, but I did and it didn't seem to hurt anything.

[AcclaimML]

Oh you bad bad boy!

[RJBrown]

This is a repeat of a similar thread from last week. The reason Lycoming wants us to preheat is to eliminate the possibility that the parts don't change tolerances cold causing the engine to bind. Air cooled engines running tolerances change dramatically from cold to hot. The heating of the oil is a byproduct of the reason to preheat. Heated oil is nice as it allows easier starts due to quicker cranking. If an engine is cold enough the case can shrink so tightly around the crank that there is no clearance. No clearance no oil no oil scuffed bearings. This is the engine damage we avoid with preheat.

[BorealOne]

Without even doing the math, these sounds like a losing proposition, just based on the order of magnitude difference between the mass of 1 litre of oil and the mass of the engine. Even if we are talking about just above freezing temps, it would be like adding a litre of boiling water to a bathtub of ice cold water (ie negligible) and much less so in the frigid temps that some of us operate in.

Re bush pilot techniques - yes, there was a old-school practice of draining hot oil after the last flight of the day and then heating that on a wood stove, but that was combined with applying direct heat via stove pipes and blowtorches to the engine. See http://www.fepco.com/BF.chapter12.html. Most guys I know now just carry combustion heaters or electric generators to feed their Tanis.

[Alan Fox]

This is a repeat of a similar thread from last week. The reason Lycoming wants us to preheat is to eliminate the possibility that the parts don't change tolerances cold causing the engine to bind. Air cooled engines running tolerances change dramatically from cold to hot. The heating of the oil is a byproduct of the reason to preheat. Heated oil is nice as it allows easier starts due to quicker cranking. If an engine is cold enough the case can shrink so tightly around the crank that there is no clearance. No clearance no oil no oil scuffed bearings. This is the engine damage we avoid with preheat.

All things shrink with temperature , with the exception of some liquids changing state to a solid (water etc) It is not possible for the case to shrink enough to bind the crank....Although some materials have different rates of expansion / contraction.... The preheat makes it a lot easier to start....Preheating the battery , would also help alot as the battery works on chemical reactions that are slowed with temperature drop....

[danb35]

All things shrink with temperature , with the exception of some liquids changing state to a solid (water etc) It is not possible for the case to shrink enough to bind the crank....

Why do you say it's not possible? The rate of thermal expansion for Al is about 3x that of steel--on its face, it seems entirely plausible that the faster-shrinking case could bind the crank.

[Alan Fox]

Why do you say it's not possible? The rate of thermal expansion for Al is about 3x that of steel--on its face, it seems entirely plausible that the faster-shrinking case could bind the crank.

Because the bearing clearance far exceeds the rate of differential expansion, also the case halves does not "shrink" around the crank bearings , they will "shrink" around the center of thier mass , as they are split around the crank bearing halves , their center mass is somewhere between the cylinder flanges , and the bearing flanges .... But the clearance in the bearings is way more than the differential expansion , contraction....

[Alan Fox]

Maybe if we dipped it in some liquid nitrogen????

[jwilkins]

The OP said they are using both preheater and the warm oil. I think it can't hurt.

Years ago my '62 C was parked on the ramp in MA for a couple days when the temperatures were hitting highs of -10 F.

There was no heated hanger space available. The morning I wanted to leave I had the FBO try to preheat the engine, but their preheater ran on propane which would not vaporize to keep the burner running for more than a couple minutes at a time. We plugged the sump heater in and I did exactly what the OP does; heated a couple quarts of oil in boiling water. The '62 C had a very specific cold weather starting procedure in the owners manual which included pumping the throttle and flipping the prop. Between the heated oil, sump heater, and many attempts to keep the FBO's preheater running we got the engine warm enough to feel warmth on the cowl and register on the oil temp gauge. Despite the predictions from the small crowd watching out the window, it started right up and got immediate normal oil pressure. It was a nice smooth flight home.

Yes, the bush pilots will drain the oil and take it inside to warm up (or used to anyway) but they warm ALL the oil. If you leave frozen oil in the sump it can clog the pump. With multi viscosity oils and 'normal' cold temperatures (not -40 like in Alaska) that should not happen. Personally, I think adding some warm oil can't hurt and may help, but I would still flip the prop to help get it mixed up a bit.

I solved most of my cold weather starting issues by moving to Arizona. I highly recommend it.

Jim

[RJBrown]

I solved most of my cold weather starting issues by moving to Arizona. I highly recommend it.

Jim

Can't wait to follow you down to Az for the winters. Already have a homesite on Pegasus Airpark waiting to be built on. have lived in Denver for fourty years and I hate every snow flake I see. More every year. Summers in Denver and winters in Arizona sound wonderful to me.

[jwilkins]

The weather is really nice here, especially compared to Upstate NY in the winter.

The high DA in the summer, a home field elevation of 5000 (KPRC) and the summer frequent desert turbulence helped me rationalize trading my 67F in for the 80K.

My F was an absolutely gorgeous aircraft and perfectly capable for the area with proper planning. I love the way the K climbs.

Spring and Fall in Upstate NY were really nice, but the lack of sun in the winter was depressing and I grew to dislike the cold and snow more every year.

We get snow a few times a year in Prescott, but it's usually gone in a day or two.