I replace my oil & filter every 10,000 miles as I believe long life service is asking for trouble. Whilst it is quite easy to find an oil up to VAG standards 502.00/505.00 what grade is best to use? I can never decide. Prices vary massively depending on grade. I am wanting something that is best for the car (on non longlife service) whist being most economical with relation to mpg. Any tips? Does it matter much? I always thought changing it regulary is the most important thing? Recently been using Valvoline Synpower Fully-Synthetic 5W30.