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I just went to Mobil 1 site and you can see 2 new
Racing oils...
Mobil 1 Racing 0W-20
Mobil 1 Racing 0W-30
http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_Racing_Oil_FAQs.aspx#FAQs7

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Pacnorth...

can you please elaborate on the difference between the base oil differences between Group 4 and Group 3?

From my research and talking to a good friend who is a surfactant (the slippery stuff in oils and soaps) chemist....I've always contended that since all Synthetics are Petroleum based, the term 'Synthetic' (defined as derived from something other that petroleum stocks...ie, wood or other derived surfactants) was a bit of an advertising misnomer.....I look at Synthetics as being more like "cherry-picked" or cultivated molecules that have uniform desired characteristics....chosen within a much more narrow range than "off the shelf" oils.

The Germans had very little oil reserves during WW2....their surfactant chemists did develop "true" sythetic (i.e., not petroleum based) oils based from wood and other plant forms that they used to supplement their limited oil reserves...this is where the term originated but it had been overused in modern years.

In simple terms...Traditional motor oils are made up of a more random batch of "good" and "not so good" (but still acceptable) molecules, in use it's really the 'bad' ones that break-down first which in turn dilutes the entire sump full of oil....synthetics are 'the chosen' molecules verified through testing to hold up longer so they tend to last longer under more extreme conditions....but they are not really "synthetic" in the true sense of the word.

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Just curious...
What is semi synthetic formulation,
50% Pure Crude oil / 50% Group III or
50% Pure Crude oil / 50% Group IV

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Just curious...
What is semi synthetic formulation,
50% Pure Crude oil / 50% Group III or
50% Pure Crude oil / 50% Group IV

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Just curious...
What is semi synthetic formulation,
50% Pure Crude oil / 50% Group III or
50% Pure Crude oil / 50% Group IV

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You won't find "Pure Crude Oil" in any motor oil (at least you hope not), Petroleum based yes, but it is refined.
As far as Group 3 or Group 4 under the "Synthetic" heading? You/We don't know, could be either, thanks to a Judge that ruled in favor of Castrol calling their "Syntec" line Synthetic. Syntec is a group 3, an oil that has been hydrocracked to a further degree than 'regular' oils. Molecularly changed, as CompSyn point out, and therefore the courts stated since the molecules are different, they have been 'synthesized'.

Since that decision, many "Synthetics" including Mobil1 are a group 3 or a blend of 3&4.

SemiSynthetics are , of course a blend of regular petro juice and 3 OR 4.

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