Chain tensioner is about the same as a spark plug. Don't even have to drain oil they are at the top of the oil zone.

I haven't done the N62 but I would expect it to be a bit of a hassle until you get the right combination of swivels and extension. Get a 19mm (3/4) medium depth socket unless you find a YouTube video that shows a deep well works.

On the M62 the AC compressor is in the way of a deep well socket fitting. Won't surprise me a bit if N62 just as tricky and there are two

That said they should probably be replaced at something like 100,000 initially and every 50-60,000 miles after. The N has a more robust chain guide system and two MUCH shorter/lighter chains so not as likey to blow into bits like M62 (I've done two M62 chain guide replace jobs). One before chain broke one after (6-8 bent valves to replace )

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)