Hello, I would only paint it in if your wheel's style had a blackened "R" originally. I love little touches like this one but it really helps if such a highlight matches the original. Sometimes even the finish on the dried paint can vary from the original enough to nix the job. Lacquer thinner and a Q-tip will remove anything you paint in and end up not liking.
Good luck with those oil cooler lines tomorrow. Where exactly is the thermostat for the oil? Do I have such an arrangement on my 2002 V70? Kira