Gas, My speedo does not calculate engine hours, so I just go by miles run. Since my bike is dualsported, it is run on both dirt (slower speeds) and on the road (easier faster speeds). I found that the oil seems to change color and feel differant after 600 miles or so. So I just change it with rotella t at 600 miles. Seems to work great. I am approaching 13,000 miles on the bike since I bought it used in 2009. Engine runs like new, doesn't burn oil and the valves (that I check every 6 months), have not needed an adjustment yet. Original piston and rings too! Not bad for a 2002wr426f.