I had problems shifting when cold (-3?) when running thick oil in my standard Morris 1100 (I was living in the Blue Mountains at the time) I switched to HPR30 and it cured the problem. I now live in Goulburn and it is even colder (it gets down to -7?)

Looking at the data sheets for the oils....
Penrite HPR50. cold cranking viscosity, cP at -5?c = 10,565
Penrite HPR30. cold cranking viscosity, cP at -15?c =8544
Castrol Edge 22w50. cold cranking viscosity, cP at -10?c =9500
Castrol Magnatec. cold cranking viscosity, cP at -25?c =6600

Looks like HPR30 is not too bad but Castrol Magnatec would be better at very cold temperatures. Castrol Edge would be allright if you have a semi race car and you live in Sydney.

During winter in Tassie, I'd look at 10W/40 or 10W/30 grades.
Not synthetic, though.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks all, I will try thinner oil and see how I go

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Lucy - 64 cooper s replica
Lulu - 66 deluxe