I wouldn't worry about the block freezing at 10 degrees. However the radiator might fare so well.
I had a 60 F%$& 1/2 ton six that set out all day in 5/10 degree weather with clear water in it. I cranked it up and drove toward the house. After a few miles I noticed the heat gauge had run up to red line hot. I couldn't understand how it got hot when it was 5 degrees outside. When I got home I discovered the radiator had frozen up so water wasn't flowing to cool the engine.
Ain't it fun to ramble?
