This isn't a real fix, the tried something similar on the early V8s too.
It robbed a bit of power there, not heard ofit being done to M52s
though.

You should find plenty of oil rated to API SG or SL combined with CF4 or CI4
which are superior and newer ratings. These will usually have an SAE
viscosity of 15w/40 for heavy duty use even in very hot climates.
The CF, CG4 CH4 and all C ratings are heavy duty, high detergent diesel
ratings but can be combined with petrol ratings to produce what are called
'multifleet' oils suitable for both petrol and diesel engines. These are
superior oils to petrol only type as long as the viscosity is suitable for
the application.

Huw

The Thermostat and ECU reprogramming were both part of a service
campaign (12 09 94 - 4132) as an early attempt to head off the sulfur
corrosion of the nikasil liners.  I do not believe that either of these
modifications were successful if the car was run with high sulpher fuel
it still wore the linings.  In that campaign the 85 degree thermostat
was replaced with a 95 degree one.

I have a 94 540i which originally had the nikasil block.  It was
subsequently changed to an alusil one by BMWNA.  Interestingly, the
thermostat in mine was still the higher temp one and the ECU was not
reprogrammed back to original after the block swap.

As a part of a recent major service inspection (which I performed) I
replaced the higher temp thermostat with a Wahler 85 degree one,a s well
as replacing the original hard plastic thermostat housing with an
aluminum aftermarket one.

Are you sure it's a nikasil block? I didn't think any of the small sixes
had them.