Did the 1st oil change on my yr 2000 426, and wow! The magnetic drain plug was covered in graphite like metal shavings. The oil had a metallic look to it. I had heard that Yamaha YZ do wear more then others, but for a used bike with many miles under its belt I did not expect to see such wear. Is this common? I put fully synthetic in. It did have BelRay semi-synthetic in before. I couldn't find the semi kind at my Kragens or Pep-Boys, so I put in Mobil 1, fully synthetic. The sheit is expensive. Does the bike run okay with regular dino oil?