I have a 2007 Mercury 115 HP outboard and have been using Mobil 1 synthetic or Castrol Magnetic Synthetic 0W-30 or 5W-30 for several years and it doesn't burn a drop between changes. Most cars are 4 stroke motors and I believe the Honda oil is used compatible with the wet clutches on ATV's. If you use a Mobile 1 in a Honda ATV the clutches slip more because I had one and witnessed this. Now the outboard motor and boat dealerships tell you to use their bulk oil because it has special additives in it the other oils don't have but you pay twice as much and put the money in their pocket. 20 years ago most people were afraid to run full synthetic in their boats but this has changed a lot through the years. I believe the Mercury Quicksilver outboard 4 stroke oils are way over priced and not worth the extra money. It's similar to buying genuine Lawnboy or genuine Briggs and Stratton oil for a lawn mower since they price it for the person who feels it's better than an off the shelf or a bulk brand. You could probably do just fine with a SuperTech or Kirkland full synthetic 5W-30 if you really wanted to spend less on an outboard oil.