Pinecone

I did some research last winter. Both Continental and Lycoming recommend preheating if the temperature is below 20F. And that the engine has sat for several hours (I seem to remember 4). Interestingly, Continental recommends against full time pre-heating.

The problem with using dry ice is that these systems circulate the water that is in contact with the cold source in an open loop The water is pushed through the radiator, then dumped back into the bath. If you use dry ice, the bath and thus the circulating fluid freezes.. One solution would be to not put only water in the unit, but an antifreeze solution. I would use one of the propylene glycol ones that are used to protect potable water systems. The dry ice sublimates to a gas, and does not dilute the antifreeze solution. And with this setup, you could also use freezer packs interchangeably. Water ice could be used, but then you would have to empty out the antifreeze, as it would be diluted and no longer prevent freezing. Or do like race car driver cooling systems, don't cool the air, cool the person. They circulate the cold water through tubing sewn to a t-shirt and cool just the person.

Not particularly. Yes, spending time at higher altitude does increase the body's ability to deal with lower O2 levels. Or, in the case of athletes, training and lower pressure/O2 levels, enhances performance at sea level.

If you fly at altitudes that need O2, it would be a GOOD idea to do an altitude ride. I think the FAA still does them, but you have to go to OKC to do them. Each person has their own hypoxia symptoms and tolerance. And, as has been mentioned, it can change from day to day. I did my chamber rides in the USAF. When we did the hypoxia demo, I outlasted the patience of the instructors. I was going well, not great, but functioning for over 5 minutes, maybe 10. They gave up. Years later I was flying with a couple of friends, both pilots. I was left seat as CFII/Safety pilot. Right seat was under the hood. We were VFR (IFR current, but without current charts) and had to climb to 13.5 for weather (less than 30 minutes) I noticed the guy under the hood stat bobbing around. I looked back, and the guy in the back was OUT. I was fine.