dannytheduck1985 said:
What's people's thought on changing from 10w60 to 0w40 oil? More viscous at low temperatures, a lower heat rating but more vicious at high temperature. Let's face it if your oil temp is exceeding 125 degree, the oil breakdown is the least of your worries.
This is recommended by Mr Vanos
This is an argument that came up many times on the M5 Board when I had my e34 M5s, and I was hoping it wouldn't come up here
Just so we all understand the coding of multigrade oil, the 10w or 0w is the cold crank viscosity and the 2nd number is the minimum viscosity that it has to be at 100ºc.
At 0ºc 10w60 has a cold crank viscosity of 874cst vs 665cst of 0w40.
At 100ºc 10w60 has a hot viscosity of 24cst vs the 14cst of 0w40 (i.e 10w60 us about 70% more viscous).
So, a thinner oil will circulate faster when cold, but a thicker oil will (to a limit) work/protect better at higher temps.
However, the optimal oil for any specific use will depend on that use. If it's a daily driver that hardly gets to warm up, is never hooned or tracked, nor sits on an autobahn at over 100mph for an hour at a time, then a lower viscosity oil will be fine.
There are stories on the internet regarding a decision BMW supposedly made, early on in the life of the S54 when they changed the recommended oil from an 0w40 to the 10w60 we use now. Some say it was due to a deal/collaboration with Castrol to sell the TWS (but I was using that in the S38 M5 before the S54 came out anyway), and other say it was due to oil pressure & oil use issues.
You might find you use more oil as it blows past the rings/valves and burns, but it won't be much (e.g. on the e34 M5 it was not uncommon to use a litre of oil a week/500 miles).
Different oils will have different lifespans - not related to the viscosity rating. They will all pass their tests when new, but many will break down very quickly and should be changed more regularly...some 'extended life' oils will break down slowly over 15,000 miles whilst others will reach the same lower levels after only 5,000 miles.
Ultimately is down to personal preference. I choose to use 10w60 and change my oil & filter every 6-7,000 miles and also after a Ring trip.
that sounds like a bad plan but each to their own :? I did a good deal of S54 study before & during my previous M ownership & continued that after i sold it , never once did a change of oil grade to 0w 40 come up as a possible good move :| 
I don't think the car run for long with a tree wedged between the turret and the engine 
Liverpool