On a more practical note, I considered that a cold engine consumes much more fuel during the warm up phase and it also causes the most engine wear.
In winter conditions, my car uses about 13 litres during warm up - for the first 10 to 15 minutes. If you must do a lot of short trips then this is significant.
I am considering a DIY oil pan heater which will raise the oil from 0 degrees F to 80 degrees F in 1 hour - using only 250 watts.
See:
Engine oil pan heaters, filter heaters & battery warmers. Designed for cars, diesel engines, more effective than block heaters, magnetic heaters. Suitable for Volkswagen vw beetle, Audi, Land Rover, Ford, Chrysler, GM, for more info.
FYI, here is the reply I got:
Thank you for visiting our web site and requesting pricing on a Model 16 oil pan heater.
Oil Pan Heaters
Our oil pan heaters are thin, flexible heating pads that are permanently bonded to the bottom or side of the oil pan. The heater has the special adhesive already on it, by simply peeling off the protective backing and pressing the heater firmly in place on a clean, flat surface, the heater is ready to be used. Note the heater must be installed on a smooth flat area, free of grooves and ridges. Only to be installed on metal oil pans.
No special tools or skills are required. Everything for a complete installation is included with each heater.
An Oil Pan Heater is far superior to a block heater and more efficient as a block heater only "warms" a part of the engine not all the engine.
An Oil Pan Heater "heats" the complete engine starting at the bottom.
The hot oil heats the crankshaft, which in turn heats the connecting rods, pistons and cylinder heads. Remember "heat" rises.
In 2 hours, our oil pan heaters can raise the engine oil temperature 100F / 40C.
By installing an Oil Pan Heater, your vehicle will start easier and there will be less engine wear.
Based on an oil capacity of 5 quarts, we recommend the model 16 with an output of 250 watts.
The model 16 measures 4” x 5” and requires a smooth flat surface on the side or bottom of the oil pan for installation.
Filter Heater Model
Our FH-50 is a flexible heating pad designed to be installed on fuel, lube oil and hydraulic filters. It is easy to install and remove as it is held in place with Velcro straps.
The heater operates on 12 volts, produces 50 watts and draws 4 amps. It is designed for filters with a diameter of 3.5" to 5.0".
The FH-100 heater operates on 12 volts, produces 100 watts and draws 8 amps. It is designed for filters with a diameter of 3.5" to 5.0".
Battery Warmer
They are of similar design as the oil pan heaters, without the adhesive. They are installed under the battery so they are very easy to install. Available in 110 volt or 240 volt, the BH-60 has an output of 60 watts, which will keep the battery warm and prevent overheating. The BH-60 measures 5.5" x 8.5" and is suitable for most vehicles and trucks. By installing a Battery Warmer, the efficiency of the battery will be increased to give you reliable starting ability on the coldest days. (not to be installed in insulated battery boxes).
Heater-Stat
To automatically control the Oil Pan Heater we offer the optional Heater-Stat, model HS-3. The HS-3 will turn ON the heater(s) when the ambient temperature falls below 35F/2C and will stay ON until the temperature warms up to 45F/7C. The HS-3 is rated for 1800 watts/ 120 volts, so one unit can handle an Oil Pan Heater and our Battery Warmer.
Pricing
Model 16 Oil Pan Heater $85.00 CAD
Model BH-60 Battery Warmer $42.00 CAD
Model FH-50 Filter Heater $85.00 CAD
Model FH-100 Filter Heater $90.00 CAD
Model HS-3 Heater-Stat $25.00 CAD
Special
Model 16 starter pack $134.00 (comprising heater, battery warmer & heater-stat)
Shipping starts at $7.50 but this cost is dependant upon quantity ordered &.delivery method