Block Heater Types; Water or Oill Pan
There is no comparison. The water jacket heater is the only one to use. This heats the whole engine block instead of just 4 or 5 qts of oil. Hot oil hitting cold galleries/rails adds up to cold oil and cold block. Cold oil hitting warm block (tremendous mass and heat inertia) adds up to warm block with warming oil through galleries.
The biggest benefit of the water jacket heater is that the moving metal parts, i.e. the crank and cam shaft and valve train, are warm at startup. Most metals are less ductile the colder they get, so the stresses are increased each cycle/rotation when rotating or reciprocating. This increases the stresses in the moving parts during the natural harmonic vibrations of a running engine.
IN A NUTSHELL; Use synthetic oils in the winter. If your area gets extremely cold for prolonged periods, get a water jacket heater. Use a timer. About three hours is a good number, as mentioned by someone, to pre-heat.
The oilpan heaters allow the car to crank easier, which makes you feel good, but do little to eliminate the root downside of cold starts.
PS; I change my oil once a year with semi-synthetic, or synthetic, period. I do it in the spring to eliminate any acids that may have developed from winter shutdown condensation in the oil. I use to be an every 3000 mi. man, but, well, maybe I'm just getting old and lazy, but, I did do alot of research.
