Rob Graham wrote:

this oil "BP Energol GR 425- EP"

I can't find any mention of this oil or an equivalent

BP/Castrol say Energol oils are part of their legacy range and being
phased out, I had a nose around on their website, they seemed to suggest
Alpha SP as replacement

https://thelubricantoracle.castrol.com/range/alpha-sp/industrial/en-JP

But looks like you'll have to choose between going up, or down on the
viscosity ... maybe contact them?