Have bought a couple of S & S filters over the phone from Matt's Machine Shop, and 6 litres of Mobil 1 V Twin oil which is pricey at over £80.
Have also sourced a Valvoline (H-D suitable) refined 20W / 50 mineral oil at about £35 for 5 litres of the right spec.
After discussions with S & S engine specialists and seeing what others are doing I will change oil and filter at about 300 miles ie. once before the 1,000 mile change although this is not recommended as being necessary by Morgan or the Morgan dealers I've consulted. I'll use the Valvoline for this as it's not going to be in there for long and is the correct spec and much cheaper than others I've seen so far. Will use the Mobil for the 1,000 mile change.
The oil capacity of the M3W is pretty high so the degradation of the oil will be less than on most bikes, and temperature fluctuations should also be less because of the sheer mass of oil as long as idling is not excessive. Hence my conclusion that 1 change before 1,000 miles is (hopefully) more than sufficient.
