I saw an interesting video on oil mix ratios. I watched it on TV so I don't have the link, but a gentleman tested 25:1 and 50:1 on a Stihl saw; I think it was an MS261 or similar. He compared temperatures at the exhaust after 3 minutes at idle, after 3 cuts on a ~16" log and after 3 cuts on ~12' logs. In all cases, the saw ran much hotter on 25:1 than 50:1. Engine temperature was as much as 38 degrees hotter at 25:1. The thought was that the 25:1 was effectively making the saw run lean. It also had noticeably less power. I am not sure if such would happen on an MS500i, with its sensors and microprocessors. But running hot was not a good thing. I tend to use 50:1 with Amsoil Saber because Stihl suggests 50:1. I once had a saw that asked for 16:1. I don't think the oil ratio needed depends as much on the saw design as the oil. As long as you have enough oil to create an oil film thick enough to avoid metal-to-metal contact, more oil will not improve lubrication. All it will do it make the saw run hotter and put more oil smoke in the exhaust. Will Saber really allow 100:1? I think it is possible. Many report doing so for years with no problem. But I am not ready to take that step. Oil is cheap compared to damage to my 500i.
