I buy the correct recommended oil (Castrol Power One 4T) on EBAY for around £30 for 4 litres. Checked my valves on the last service which was fairly straightforward but had to change four shims because the clearences were too big. The only pain in the arse was waiting for the replacment shims to arrive. Don't forget to change your final drive oil and ensure you only use exactly what's recomended. Mine stank and was black when I changed it at 11,000 miles so will be changing it at the same time as the engine oil in future ie every 6,000 miles
