From a past thread
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4174378/all/What_is_the_most_stringent_Eur :
Originally Posted By: BMW Release Procedures
For differentiation purposes, the oil specifications are designated according to the year in which they were first used as:
"BMW Longlife-01, -01 FE" (2001),
"BMW Longlife-04" (2004),
"BMW Longlife-12 FE" (2012)
and "BMW Longlife-14 FE+" (2014).
From a past thread
https://bobistheoilguy.com/forums/ubbthreads.php/topics/4174378/all/What_is_the_most_stringent_Eur :
The categories "BMW Longlife-01", "BMW Longlife-01 FE" and "BMW Longlife-14 FE+" as well as "BMW Longlife-04," and "BMW Longlife-12 FE" are qualitatively comparable but differ with regard to minimum viscosity at high oil temperatures (HTHS viscosity).
BMW Longlife-01 / -01 FE / -14 FE+ oils are only suitable for gasoline engines, while BMW Longlife-04 / -12 FE oils are suitable for diesel engines with
particulate filters, due to the reduced sulphate ash content.
LL-01 (ACEA A3/B4 base) requires the N20 performance test, N20 Aeration test and N42 Valvetronic RNT test
LL-01 FE (ACEA A5/B5 base) requires all the LL-01 tests plus the N20 Fuel Economy Test and has lower limits on HTHS and specifies a minimum KV100 of 10.0 and a minimum TBN of 10.0
LL-04 (ACEA C3 base) requires the same testing as LL-01
LL-12 FE (ACEA C2 base) requires all the same tests as LL-01 FE plus the N47 AATL carbonisation test and the N47 Fuel economy test. It also has even lower limits on HTHS and requires a minimum KV100 of 8.8 and a minimum TBN of 6.0
LL-14 FE+ (ACEA A1/B1 base) requires all the same testing of LL-01 FE but at minimums of HTHS 2.6, KV 7.8 and TBN 9.5