Which Oil Is Best?

[Major Rant]

the Major who doesn't actually have the courage of his convictions and so changes his oil twice as often.

Not true !!... I do it because I have DATA ( y'know ... evidence with numbers :pokefun ) that shows that ALL OIL degrades in use and none of them can be trusted to stay within their viscosity window more than a few K miles and it is therefore good for my engine.*

Here it is :
[table][tr][td][/td][td][/td][td][/td][td]Relative Viscosity Retention (as a percentage of initial viscosity retained
after normal use in the same motorcycle)[/td][/tr][tr][td] [/td][td]0 miles[/td][td]800mi[/td][td]1500mi[/td][/tr][tr][td]

Mobil 1
Castrol Syntec
Castrol GTX
Honda HP4
Spectro 4

[/td][td]100%
100%
100%
100%
100%[/td][td]86.6%
78.1%
72.2%
69.2%
68.0%[/td][td]83.0%
74.5%
68.0%
65.6%
63.9%[/td][/tr][/table]

* Actually synthetic oils can (see Mobil 1 above).. I'm leaning towards the use of Asda or Tesco Fully Synthetic, which has been wondrous in the car - still amber and oily after 11K miles