An old fellow Mini-engine building friend of mine, sadly no longer with us, used to describe those thin oils as 'weasel p**s'.
I once tried a Shell synthetic in a Cooper 'S' rally car because it was a new oil and the Shell stockist wanted me to use it. I blew the main, big end and cam bearings, which then dropped white metal through the SC CR gearbox and the whole episode cost me over £600 to put right and that was just the parts cost. Never again. I switched to Kendall 20w50 which was the finest oil ever for a Mini and then switched to Valvoline VR1 when Kendall became no longer easily available in the UK.
There is a rumour that the old BMC team used to be contracted to Castrol, but filled loads of Castrol cans with Kendall before an event and it looked to the World as though Castrol was being used on major rallies. 'BMC Wins On Castrol' has a hollow ring if that is true
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