Thanks Gav, which additive?
I now have it on good authority from a TVR mechanic (TVRs use the BTR) in the UK that they use Mobil SHC 80W 140 ID for both the BTR LSD and Hydratrak.
http://www.mobil.com/Australia-Engli...ube_SHC_ID.asp
He makes no mention of additive though?
Paul