A comment or two about cold oil from someone who lives in a mild climate.
Living in California almost nobody preheats and they use 100 w oil even in the winter. I have seen snow on the ground and pilots attempting to pour 100w oil into the engine and then operate the engine without preheat. That is why we used to see so many scuffed pistons in our engine shop. 100W oil at 30 degrees doesn't splash very well!. The pilot and line mechanic never see the damage but down the road when you have high oil consumption the engine shops sees all the piston scuffing.
This type of damage has been going on for at least as long as I have been involved with engines (30 years now) but the damage is hidden from the pilot and mechanic so there isn't an awarness that their is a problem. The reply I often get is "These aircraft have been operating for 20 + years without preheat and with 50w oil in the winter so what is the problem?"
Each time your piston starts scuffing against the cylinder wall nothing immediately bad happens. But over time your engine gradually starts burning more oil. There is no problem until you have to top overhaul the engine - but this is such a common thing to have to do to an engine that you don't associate the top overhaul with cold heavy oil.
One another point - if you look at the Lycoming O-235 series engines with the solid tappets there isn't any oil pressure to the valve train like there is with most other engines that use hydraulic lifters. The way oil gets to the rocker arms and valves in an O-235 is it splashes up onto a ledge inside the crankcase, from there it drains down the almost horizontal push rod tubes. The push rod tubes sit on the top side of the engine where they are blasted with all the cold air coming into the engine cowl. Now can you imagine an engine with cold oil, 50W oil? It's not going to splash and run down a cold tube! One could be 50 miles away from the airport before the oil gets thin enough to drain down the tubes and gets to the valves!
John Schwaner
Sacramento Sky Ranch Inc.
PO BOX 22610   6622 Freeport Blvd.
Sacramento, CA. 95822
(916) 421-7672 800-433-3564 Fax (916) 421-5719