Is there any problem if I drop a UL listed dipstick heater into my 93 240?

Does your dipstick heater stay in all the time? Most of the ones I saw required you to take the dipstick out and insert your working Volvo dipstick. This is a pain. MUCH better is to use a factory block heater. Much more efficient in terms of heat produced per watt of electricity. It heats the coolant, which is better for the engine than heating just part of the oil. You must drain the coolant and pop a freeze plug for the factory type heater. It should last as long as the engine, wheras I have doubts about the dipstick unit, which tends to sell to the temporary cheap use it a few times crowd. The dipstick is good if all you want is to get through the next few weeks. /s/ BMWJohn in Indy

just wanted to keep Sven (93) a bit warmer... engine block heater sounds like the real thing, thanks

As long as it's a decent quality rig, I suppose there's little risk. But as Smitty points out they could overheat the oil next to the element. If it puts out enough wattage to heat the entire panful of oil, well, that's a pretty small source doing that - so is a light bulb filament! For curiosity - what is the watt rating?

My suggestion would be to install an engine block heater and change to a light synthetic oil like 5W30 or Mobil-1 0W40. This will give the easy cranking and quick lubrication on startup you want, with the advantage of immediate warm air from the heater/defroster, and fast engine warmup to full temp.
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Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

don't know the wattage(the packaging went out with recyling) but it was UL and is a temporary measure to keep Sven a bit warmer especially this winter in Mass.Your advice is clearly the way to go, thanks (any suggestions on brand, etc.??

Generally speaking, no. Historically, dipstick heaters of yore have been too hot, and they cooked the oil next to the dipstick. I think both the heaters and the oils have improved, so problems have been reduced. As long as you keep up with oil changes, I think your brick will be better off with warm oil on startup than with the thick goop which would be in the crankcase otherwise.

thanks Smitty.. like most bricksters oil changes are always a priority