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
Sacramento Sky Ranch Inc.
PO BOX 22610 6622 Freeport Blvd.
Sacramento, CA. 95822
(916) 421-7672 800-433-3564 Fax (916) 421-5719