Not sure why graphite conducting would be a problem, unless thinking of possible oil running through and dropping onto the electrics inside the car.
Light oil like 3 in 1 is an option. Specific lube for cables sounds even better. One of my concerns was an oil degrading the inner sleeve that runs inside the cable casing. Hopefully a specific cable lube would have stuff that allows for that. Or am I just being over cautious and 10w/40 engine oil would be fine?
I guess 10W40 would be fine but being in England you might consider a 0W20 or a straight 10W for year round use. OTOH, it is warm under the hood so maybe a 50W is more appropriate. s/o. I didn't realize they made cable lube but thinking about it, it does make sense. I'd go that route. ciao, chris