Lukate
I know a gent who does advanced training and did 78,000 miles in 3 years using Semi Synth.
The thing with Mobil 1 is when you start using it in the engine must be completly run in 'cos it just won't wear after that, that's fine with an engine that is run in after 2K or so but these boxers don't get to their best till youv'e done 20k plus even then they still use oil.
I use Mobil 1 gear oil in my gearbox after 12K, but that's different to an engine, gearboxes don't burn oil.
The wisdom is Mobil 1 is not for boxers, if you want to use a fully synth oil then use Halfords own brand Synthetic motorcycle oil, its Esso and less than half the cost of Moibil 1.