This is what I have learned over the years....
Based on a lawsuit several years ago, US oil manufactures can market Group III oils as a 'true synthetic'.
Based on all my findings over the years, Mobil 1 0W30 is the only Mobil 1 product that is actually a 'true' synthetic, but it is still considered a Group III product. Not sure why yet. I will find out.
True synthetics are PAO or Ester based and NOT hydrocracked...
Costs of synthetics vary considerably. The most expensive are the “Ester” types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils. The cheapest synthetics are not really synthetic at all, from a chemists point of view. These are in fact specially refined light viscosity mineral oils known as “hydrocracked”. These have some advantages over equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 or other oils with a low “W” rating such as 5w-50 etc and they cost about 1.5 times more than good quality mineral fractions.
This is the “synthetic” which is always used in cheap oils that are labelled “synthetic”.
Yes it’s a cruel world, you get what you pay for!
Now, you may ask, why are these special mineral oils called “synthetic”?
Well, it was all sorted in a legal battle that took place in the USA about ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called “synthetic”.
Needless to say, the marketing executives wet their panties with pure delight!
They realized that this meant, and still does, that the critical buzz-word “synthetic” could be printed on a can of cheap oil provided that the contents included a few percent of “hydrocracked” mineral oil, at a cost of quite literally a few pence.
So, the chemistry of “synthetics” is complex and so is the politics!
The economics are very simple. If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case.
But, if you drive a high performance car, and you intend to keep it for several years, and maybe do the odd “track day”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.
Until recently in the US, Castrol did not make a true synthetic. BMW is a Castrol oil that is made in Germany, but it is NOT German Castrol or it's slang name of GC. GC is a better oil than the BMW oil... not by much but it is better... also, I think GC has a Green top/cap.
In bearing shear tests, the top of the line (and most expensive) Mobil 1 0W30 and 0W40 do worse (1540psi) than the Mobil 1 Synth S (6389psi). That was a real shocker....
Valoline DuraBlend has a shear test pressure of 23858psi..... Redline shear pressure is 6389psi.
The best shear tested oil is RoyalPurple. It does not start to shear until 131,432psi. RoyalPurple R51 shear is an amazing 295,722psi.....
I don't have the shear test ratings for Amzoil.
Amzoil, and Redline are a group IV oil. RoyalPurple is the only readily available oil that I can find that is a Group V.
Also Redline oils carry no API, ACEA, or manufacturer certifications/approvals.
Their website lists the "API Service Class" of each oil, but does not actually claim API certification. Checking API's engine oil licensees database shows that no Redline products have been certified.
No mention whatsoever is made on Redline's website of ACEA or manufacturer specific approvals.
While I realize API, ACEA, and manufacturer approval testing is expensive and not necessarily the holy grail of engine oil performance, I do think it is an interesting data point.
The LL-98 spec. was provided because the gasoline sulfur content in the US (before 2003) was up around 80ppm and had some problems with that LL-01 spec. Due to the new EPA regulations US gasoline is now down around 30ppm which is on par with what is sold in Europe and in all reality, the LL-01 and LL-04 specs work fine in the US with no adverse effects.
BMW specifies different grades of engine oil, depending on the engine and vehicle model. Specifications or descriptions other than those given here, for example "high lubricity oil, fully synthetic" etc. bear no
relevance to their suitability for use in engines of the BMW Group.
Longlife-04 oils
These have been developed to guarantee an optimum service life for the particulate filter in diesel engines. These oils are stipulated for all diesel engines with particulate filter, but may also be used in
almost all other BMW engines. Like Longlife-01 and Longlife-01 FE oils, they satisfy currently BMW's most stringent quality requirements. Longlife-04 oils must not be used in BMW spark-ignition engines in
countries outside Europe (EU plus Switzerland, Norway and Liechtenstein).
Longlife-01 oils
The quality of these oils is comparable to that of Longlife-04 and Longlife-01 FE oils and these oils can be used in most BMW engines.
Longlife-01 FE oils
Because of their particularly low viscosity, these oils are able to favourably influence fuel consumption. However, they are only to be used in engines that have been specially designed to run with such lowviscosity
oils (spark-ignition engines with Valvetronic).
Longlife-98 oils
Satisfy specific requirements for extended oil change intervals that were introduced in 1998. Their quality is no longer adequate for the current range of spark-ignition and diesel engines.
The M54 engine is approved for LL-01 spec'd oil....
Plus I can clean the backside of my wheels while it's draining! 