Dani -- this is what I think might happen: the engine runs on different fuel enrichment depending on what the coolant temperature sensor is reporting. It needs full enrichment for a cold start. Since the block heater probably doesn't heat the coolant uniformly all through the engine, I wonder if the computer thinks the engine is warmer than it really is, so it doesn't provide enough fuel enrichment for that first start on a very cold morning.
Even so, there's an overall benefit to using the block heater... personally I would always use one when I have the chance. Even if it means 2 tries.
Battery warmer would help if slow cranking is the problem. But it doesn't sound like that's the issue.
EDIT: I may copy your comments to the block heater thread, too.
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I've had a lot of fun this winter (cross-country skiing, snowboarding, skating).... But I'm ready for this one to go away.
![Smile](images/smilies/smile.png)
Fortunately (!!!), the long range forecast shows this weekend is probably the last time we see the really cold temperatures (eastern Ont). Goodbye -20C during the day.
Bon weekend! Have a good one.