Do you own a chain saw or snow blower? They run just fine in the colder temperatures. Yes?

Owning one and having a model plane engine set up with the same care and attention to heat management are two completely different things. How many of your planes have a tighly shrouded engine, encompassing the entire engine assembly, that best manages heat? My guess is none.

Yes, a model engine can run as well in cold air as in warm, but attention to detail is critical. Breaking in an engine in cold air is even more critical since little of the engine is mated correctly when you first start it. You have to know a little more about what makes an engine work and how they work than just flipping a prop and running the throttle up and down.

The original question asked about synthetic oil, I had heard not to use synthetic oil for break in as it prolongs the process. Anyone else heard this? Also DLE manual I believe says to use shock absorber for break in, what precisely is this?

Precisely because the engine does not run due to absence of gas/oil in the chamber, and is not break-in yet, it's cylinder head can receive excessive wear if one just spins the thing by brute force.

The tolerance between the ring and the cylinder could be smaller in freezing cold.

So correct there...I gave that airplane to a guy who had quite a few youngsters that kinda would hang-out with him at his place in town. So that same plane is still providing new fliers with fun. It was tough as nails with some kind of cardboard laminated ribs. Best rib material I have seen...it bounces right back to shape after a mishap. It did see many crashes of sorts...but survives yet! I used tranparent covering on the wing & my boy at age about 12...wrote his name on one of the shear ribs bfore I covered the wing .That was 1978......some time ago........................................ .............. ............ Capt,n

WE dont have anyproblems running our 2 stroke snow blowers in the cold just let them warm up

The cold will be good for the engine . But some good advice do not use any spray starter fluid like you would use in a car spray starter fluid has either in it and either will dissipate the oil and may cause damage to the piston and rings .
hyflyer9

Wow, now I know what you guys meant. Cant fly today in C Fla, it is 59 and cloudy. Brrrr

Answer for the synthetic oil question. Synthetics just take longer to complete a break in, BUT, the end result of the longer break in is a slightly better fit of the relative components.

No I do not think so.
1. If you used the choke first, there will be oil in engine with fuel
2. Most modern starting sprays have lube in them
3. As soon asthe enginestarts more fuel & oil will be brought in....DAAAA THINK about it!

John,

I use ether a lot for starting some of the specialized engines I work with. We have to be careful about how often the stuff is used during a single start up process. If it's needed more than once with a cold engine there isn't any residual oil left in a cylinder to lubricate anything. I've absolutely seen significant and severe increases in wear in engines using ether starts. The reeds take it the shorts too and experience wear and damage they rarely experience if ether is not used for starting. I do a lot of ether starts, as do others, so we've been able to note the impact of the stuff over a lot of engines.

Back when I tolerated 35 F as a "flyable day" -I flew my gassers on 100% synthetic oil - which I also used from day one on all of em -
All of em broke in with no scratching - excellent compression - easy "flippity flip" when cranking over when starting
I always choked to get a "wet" sound before closing throttle to idle - Then a easy flip typically had em ticking over
An engine was never spun over in a dry state.
Never
Never