I have a plug (a standard 3 prong outlet) behind the grill in the front of my 550. What is it? Is there a built in block heater to keep the engine warm during winter? Does everyone have this and has anyone ever used it?

 

Can you show us a pic?

 

my guess is block heater, however I didn't think there was a block heater available from bmw for your car. It could be aftermarket, just check to see where the cord runs too. I have a oem block heater on my car but I have the older m54 engine. I also know that my dealership installs small trickle chargers this way, used for keeping batteries full charge in the winter. If it is a block heater the cord should run close to your oil drain plug as thats where the oil pan is.

 

Yeah...I'll snap one with my phone....it's currently around -20Celsius (-4Fahrenheit) so I'll have to build up some courage before I make it out to the garage!!

 

Since you're in the Great White North, it probably is an engine block heater.

However, you should check to see what type it is. If it is a dipstick heater, remove it. [I do not have personal experience with it but] the folks on the 3-series and e24 have nothing nice to say about dip stick heaters or the people that use them.
The dipstick heaters tend to scorch the oil where they make contact in the tube...

In the e24 there was a freeze plug that you could install a resistive heating element to warm up the cooling fluid for cold days... HERE

 

Most likely an oil pan heater. You cant get a block heater on an E60.

 

Here the importer installs a block heater to all BMWs. Actually it's the same with all other brand importers too.

 

It's probably not a block heater. I dont think the engine even has a spot on it to install one. Probably oil pan heater.

 

I know for a fact that you can get block heaters for older e60's, I just installed one on my car but I think you have to have m54 engine. As for the OP you are probably right in that he likely has a pan heater because he has a newer e60.

 

It is a block heater.