I've found that synthetic oil and a block heater do wonders for cars in Canadian winters. I think the chances of a block heater starting a fire are negligible, especially if you keep things in good condition, as mentioned. I use them on all my cars. In the summer, I tuck the block heater cord neatly away into the engine compartment and secure with a nylon tie. To make sure the cord stays in good shape, I secure it to the front frame so it doesn't dangle or rub on anything.

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon