I want to do everything in my power to make my 1991 245se last as long as possible(when also saving it from rust). I was thinking about putting a block heater on the engine to warmthe car up before I got into it during the winter. Has anybody gotton one for the B230f engines? And if so what results did you find? Can you get a battery operated unit? I know it could cause it to kill the battery one day if I leave it on to long, but that is why God made Farm and Fleet batteries for 30 bucks for spares.

Kevin
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1980 244DL, 1982 245GL, 1987 744GLE, 1991 245SE, 1996 855GLT, 2001 V70

I doubt that a block heater would do anything to extend the life of your 240. Block heaters will make for easier starts in extremely cold climate, thats it. No they are are not battery operated.
When I grew up in the Canadian north sometimes we would stick an extension cord with a light bulb on the end under the hood to keep the chills off the engine at night. Helpfull when its 10 below and you have an old battery, old car and no cash.

I've never seen a 12 volt block heater. Volvo has one that replaces one of the freeze plugs on the exhaust side of the engine. It's probably a couple hundred watts. Maybe you could get a ac/dc inverter that could power a 400 watt heater, but on a 12 volt system, I think 400 watts would draw 33 amps (400/12) which would completely discharge a large, healthy battery in about an hour and 1/2, maybe less time if it's really cold out. I had an old Mercdes diesel 220, with a 500 watt block heater, which had to be plugged in at least 2 hours before the temp gauge would move off the bottom peg.
Stay away from dipstick heaters, too. You're better off heating the coolant which will heat the block better than cooking your oil.