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Originally Posted by ctgottapee
My GM alternator as the OEM part for my car has the kill switch, a '93 Cadillac Deville. My only guess as to why is because the car's service manual has a number of procedures which require the kill so they added it as spec for easier service.
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Thanks. I'll look into that.
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I was also thinking about the coolant heater as the best step. It seems you lose a lot of efficiency with the pan heaters unless your electricity is free.
Another nice feature about my big old car is that it has oil and transmission fluid coolers built onto the sides of the radiator. These has the effect of also warming those fluids during the winter.
Did you go with the inline heater or full version with the pump attached? Which brand? It'd be nice if I had a block plug to key into but this model engine doesn't have one.
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No, my car has no OEM block plug heater option either. I would always prefer to keep things simple where possible.
I ended up getting a 2kw Kenlowe heater and pump kit. Kenlowe make 3kW and 2kW versions. (Expensive, but it's a good unit, and it's a local company with a good warranty and so on. I'll be using it year-round so a good warranty is a big plus.) I went for the 2kW version so as to leave enough leeway to add a 1kW fan heater in the cabin to run in parallel with the coolant heater on cold mornings. I've fitted a mains socket under the dash for that purpose, and have tested a fan heater's ability to warm the cabin to a good number of degrees about ambient, but have not used the fan heater properly yet as the weather is too warm to need it. It's just an ordinary house 1kw/2kW fan heater which I 're-wired' to produce 500w/1kw. 1kw is plenty inside a car. Also, I wanted to be able to add a sump/oil pan heater of up to about 250w at some point. (Theoretically 3kw is the limit on a single mains socket in the UK, but in practice you can push that by another kW or so without problems. Even the standard 13A plug fuse won't blow below about 20A continuous.)
The coolant heater works very well, but doesn't heat the oil. It heats the coolant to 87 degrees C (with a 10 degree hystersis, so maintaning 77-87 degrees). However, once the engine starts the temp drops by another 10 degrees at least, which I presume is mainly due to the coolant/oil heat exchanger ('oil cooler') passing heat to the oil. It's not a big deal, and I believe I am avoiding the really bad mpg I would get below 50 degrees C, but a small sump heater running in parallel with the coolant heater would be no bad thing. I would run them for between 30 minutes and 90 minutes before drive-off time, depending on time of year.
Sump heaters tend to be inefficient mainly because you can't fit powerful ones for fear of overheating the oil if they are left on a long time, and if you have a low power one they have to be left on for a few hours to do the job, although anything over about 4 hours is a total waste, so you really need a timer. It's always more efficient to use the max amount of heat for the shortest time, as heat loss to the surroundings is then minimised. From the point of view of preserving the engine and easing starting in very cold weather though, the oil is where you really want the warmth I think.
If you have a 'big old car' with plenty of space around things, perhaps you could do what one person suggested on another thread, which is to get an ordinary travel iron and attach it to the oil pan (with heat transfer epoxy or similar.) Those things have proper thermostats (and folding or removeable handles) so you can use a 1kW iron quite safely as there would be no danger of overheating the oil. (You would of course have to take steps to waterproof the thing, but that shouldn't be difficult. Maybe set the t.stat to what works, then encase the thing with glass fibre and epoxy resin.) But using a travel iron is only an idea. No one has tried it yet, as far as I know.