Should I charge my battery up to 4.2 volt

[Rossum]

Thanks for that info Rossum. Much appreciated and will pass on to my brother whose Tesla dealer needs re-educating!

Tesla doesn't have "dealers". All their stores are company-owned. Being somewhat close to the auto industry, I've come to expect ignorance on technical details from sales people at independent dealer franchises, but I'm rather surprised to see it from Tesla employees.