Re: Two Cycle Oil
The Merc Premium Plus is excellent oil. The ash components in it are practically not worth mentioning, especially if the outboards you're pulling down run at slightly higher temps. The fact you're not seeing any build-up is a sign the small amount of ash is being burned and blown out. Hopefully the reason you're having to pull the engines down in the first place isn't a result of the oil burning too clean. I just don't think you can wrong these days with any TC-W3 oil in an outboard.
<br /><br />Maybe you don't get it. Low-ash oils are better for higher temperature (ring land) air-cooled engines. Ashless oils are for lower temperature (ring-land) liquid-cooled outboards. Low ash oils are not what our liquid-cooled outboards run best on. And you'll find most reputable modern TC-W3 outboard oils to have "NIL" or ".00X" %ash weight.<br /><br />We know TC-W3 oil is tested by NMMA's sanctioned laboratories for deposit buildup, ring sticking, scuffing, lubricity, etc. The point is that for most TC-W3 oils to meet those test standards, they have to be ashless. There are very few exceptions.<br /><br />You would be wrong to insinuate that the NMMA tests or analyzes the oil itself (for ash detergents, etc.). On the contrary, the NMMA's laboratories test the outboard's general condition, with emphasis on the pistons, rings, and cylinders...only as a result of using that particular oil. The oil can contain anything, as long as it operates in their test outboards sufficiently (and meets other industry standards).<br /><br />For example, during the two Mercury 15 HP detergency tests, a TC-W3 oil must not have a compression loss of 20 psi or greater within 100 hours of testing. It's piston scuffing must be limited to 15% circumferential and 20% area. Ring wiping must be limited to 5%. The piston pin needles bearings must fall easily from the bore of the wrist pin. The average adjusted second ring sticking must be greater than or equal to 8 merits (a rating system). And the average piston second land deposits must be greater than or equal to 6 merits. There is no lubricant analysis. It is a pass/fail test based on engine analysis. And in some tests, like the 40 HP general performance test, the lubricity test, and the preignition test, the oil must perform in the engine as good or better than the NMMA's reference oil. But again, the oil itself is not evaluated.<br /><br />Your comment about earlier outboards oils being low ash makes no sense, as the specifications and testing standards for outboard oils have changed since then, requiring better performance in liquid-cooled outboards. Ashless oils have filled the niche. <br /><br /><br />seahorse, if you feel low ash oils are better to run in your liquid cooled outboard than ashless, then by all means have at it. Hopefully others here will have more common sense. But what do I know. 