£20 includes the time spent taking the car into the workshop, measuring the oil level, topping it up and bringing the car back round. Which I appreciate is not a difficult job and one I could easily do myself, but it's included in the cost and isn't free to do. My point was just to highlight that isn't really as overpriced as you say.
I'm not sure on what basis the other oil is better?
This is a legitimate question. I've done the digging and found the original 800 page thread where a chemical engineer disected the data sheets of various oils and reached that conclusion based on his interpretation and recommendations. (It's not in English but I'm happy to share via pm for those looking for some google translate enabled lecturing)
I don't have the same background to explain it in detail but my best attempt aat an exec summary is that it was mainly based on analysis of data such flash point temperature, pour point temperature and percentage of mineral refined) oil contained (even the fully synthetic stuff has plenty, eg Castrol Edge Titanium has ≥25 - ≤50 % as per the table in Section 3 of their
spec sheet . All said spec sheets are public and published by the oil manufacturers themselves.
For Castrol Edge (Castrol seems to have replaced Shell in 2024 as BMW supplier in Europe from what I've gathered) we have a flash point of 197 degrees, typical of an oil with a high mineral refined oil content, whilst the Fuchs has a flash point of 234 degrees as mentioned in
section 9. Both 5w30 oils, which is what you should use for diesels of that vintage. Sadly the more recent spec sheets of
Miller seem to be very lazy and just say >200 degrees.
I'm waiting for the technical analysis after used oil has been sent in to a lab and compared with whatever oil BMW would put in it.
Or it could just be due to 'the salesman told me so'.
Plenty lecturing
available here for thouse who want some further lecturing where users compare lab analysis of their samples. (Opie also do a sampling kit for £30ish if I remember correctly for those curious, there's handy interpretation that you get sent back as well.
I am making an effort here but oh my you have a constructive discussion style.
I spent hours looking at lab results comparing different oils on different engines, there's no golden recipie for all and even after all that reading I'm still confused. There's too much choice, I'm a simple man, I want 3 options: cheap, mid and expensive.
A fair point, hence after I did my original digging I go with "Fuchs as great value for money". There's some fancy Mobil 1 stuff, the usual Redline from what I remember but Castrol (which is what BMW use nowadays) is generally... mediocre (IIRC there was some 0w40w Castrol that was decent).