Quick (yea right) pre-heat question.

[Aztec Driver]

At what ambient temperature would you consider it to be beneficial to preheat a set of IO540's?

I always thought that the need for preheat did not come in to play until under about 30*F. I do know my IO320's really do not like temps under 10*F, as they will either not start, or they are VERY hard to start.

I ask this because I fly anAztec that the owners will plug in a few hours before a night flight, and it sits inside a heated hangar, where the temp rarely gets below 45*F.

That seems a little overkill to me, but I was wondering if it had more benefits than I think, perhaps allowing the engines to get warm faster.

 

[Henning]

In a heated hangar, yeah, it's overkill, but OTOH, it's not doing any harm either.

 

[RichNY]

When you have the time, fill a cup with the oil you use. Check how it pours at various temps, 10, 20, 30 etc. I preheat when the oil is below 45.

 

[Fearless Tower]

In a heated hangar, yeah, it's overkill, but OTOH, it's not doing any harm either.

Saves time running on the ground waiting for the oil temp to get in the green.

 

[Ted]

40F is the generally recommended/accepted threshold. It doesn't hurt a thing, though, so I wouldn't complain.

 

[Unit74]

Preheat not only saves time on the ground, but aids in starting and saves in fuel. Ground idle takes a very long time to get up to temps in cold weather.

 

[Fearless Tower]

Preheat not only saves time on the ground, but aids in starting and saves in fuel. Ground idle takes a very long time to get up to temps in cold weather.

Yes. Big reason I'm planning on installing a Tanis oil tank heater on the Waco. I don't fly it below the upper 30's, but even when the OAT is close to 50, it can take 20+ minutes running on the ground to get the 4 gallons of oil up to temp.

 

[poadeleted20]

Under 40F, it won't hurt, but it's not essential. Under 32F, it helps a lot for starting, and that's good for the engine in the long run. Under 20F, I wouldn't start without preheat.

 

[dell30rb]

Under 40F, it won't hurt, but it's not essential. Under 32F, it helps a lot for starting, and that's good for the engine in the long run. Under 20F, I wouldn't start without preheat.

Spot on if you are running a multi viscosity oil like the Philips x/c

You'll find it difficult to start something with a straight weight oil such as aeroshell 100w below about 40F

 

[poadeleted20]

Spot on if you are running a multi viscosity oil like the Philips x/c

You'll find it difficult to start something with a straight weight oil such as aeroshell 100w below about 40F

Agreed. Which is why the engine and oil manufacturers tell single-grade oil users to switch to a lighter weight oil like SAE40/Aeroshell 80 when the ambient temp is below 60F (or even SAE30/Aeroshell 65 when it's below 30F).

 

[Stewartb]

TCM says to preheat below 20*f. Lycoming says 10*f. Given time and opportunity I use 25* as my own limit. I don't notice any lag in starter speed, cylinder firing, or oil pressure coming up at 25*. Cooler than that and I do notice changes. I can't criticize anyone else for having their own preheat routines. Their equipment, their choice.

 

[poadeleted20]

The full word from Lycoming's Key Reprints:

In cold weather, preheat is another factor that must be considered prior to starting the engine. There are specific guidelines in Lycoming service instructions which establish when preheat should be used, but how much, or the method of preheat is generally left to the good judgment of the pilot or maintenance person doing the preheating. Use of the heated dip stick is not recommended by Lycoming, although most other methods are considered to be satisfactory. For most Lycoming models, preheat should be applied anytime temperatures are at 10˚ F or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20˚ F. It is recommended that these guidelines be followed even when multi-viscosity oil is being used. In addition to hard starting, failure to preheat the entire engine and oil supply system as recommended may result in minor amounts of abnormal wear to internal engine parts, and eventually to reduced engine performance and shortened TBO time.

That said, my experience is the engine starts a whole lot easier at temps well above 10F if you preheat. For a fuller discussion, see Lycoming SI 1505. Note that your battery will also work a lot better if you use a warm air blower to heat the entire engine compartment (assuming that's where you battery is).

 

[Henning]

If you want to err on the side of safety, preheat.

 

[James331]

40 sounds right, also pre heating the cabin is a good idea too, instruments do funny stuff when they are cold.

 

[Henning]

40 sounds right, also pre heating the cabin is a good idea too, instruments do funny stuff when they are cold.

Like icing up internally as the vacuum is sucking the steam off your truck heated boots.

 

[frfly172]

I like to pre heat below 30 ,do both inside cabin,and the engine ,a warm plane is a happy plane.