20v urq: Synth or semi-synth?

[Mihnea Cotet]

For my friend's 20v urq, we'd like to know what's better, synth or
semi-synth oil? Particular weights recommended?
Also, the bomb appears to be dead...only 2 pumps and that's all folks! hard
as a rock afterwards! The Pentosin level appeared to be around the MIN
level, could this have an effect on the bomb's operation? DO we need to
flush the Pentosin? How to do this correctly?

Thanks for all your answers and help,


Mihnea