The new STIHL 4-MIX engine uses the 50:1 fuel-mix same as their 2-stroke engine. The outboard motor companies are going with 4-stroke engines now and it looks like Stihl will be following suite. They are trying to get away from the 2-stroke engines because of new regulations taking place from the EPA. 4-strokes put out less emissions than the 2-strokes so that is the route the companies are taking to clean up their acts. These companies are dumping large sums of money into research and development for their new 4-stroke engines. Most of these companies have built 2-stroke engines for most of their existence and are only going with the 4-strokes out of necessity to stay within the EPAs emissions standards. If they can't meet the standards then they can't sell their products in the USA. We don't need any higher unemployment so I hope they all design new engines that will make the EPA happy and also keep us consumers buying their products. /w3tcompact/icons/smile.gif