Re: Motor Oil
By LubeDude"<br /><br />No Problem.<br /><br />Oil analysis
Glad I asked. <br /><br />Obviously nothing in that used oil analysis shows a shear test, or how the oil was "sheared down". It doesn't even positively verify what type of oil was tested. It was your basic used oil analysis. <br /><br />But lets get this straight....<br /><br />This was the original break-in oil. It was used in a new engine 10-15 hours pulling skiers at above-normal operating rpm (4200). The owner used lead substitute, and he wasn't even sure what oil or viscosity was originally in the engine to begin with.
<br /><br />Member LubeDude, I could probably stop my comments there, as most can see the obvious problems with your comments, and why these threads get out of control. <br /><br />I'll only continue for those who might be deceived by your comment about the oil being sub-par. After all, it is an excellent oil, if not one of the best.<br /><br />The first thing to understand is that a used oil analysis is done to evaluate the condition of the
engine, not the oil. Usually for maintenance purposes or to identify engine problems. For obvious reasons shear break down of oil is done by ASTM tests, not a basic used oil analysis.<br /><br />Regardless, the first thing to do is make sure you're evaluating the right oil, and the right viscosity. It does no good to call it Mercruiser 25W-40 oil if you're not sure it is. You certainly wouldn't want to discredit oil that you have no idea what it is. Usually when evaluating oils, the oil is tested prior to using, to get a before and after comparison. This way the owner would've known exactly what oil he was testing and where it stood originally. And any accusations about brands or viscosity break-down could be verified. The boat may have come with a 30 weight oil.<br /><br />There is still much debate over whether or not engines are shipped from suppliers (Ford, GM, etc.) to Mercruiser with oil in them, or if Mercruiser puts oil in them prior to shipping to boat manufacturers, or if boat manufacturers put the oil in prior to shipping to dealers, or if the oil is added at the prep/dealer level. I've seen it happen all different ways.<br /><br />Next you need to consider that this was the original break-in oil. We all know that abnormal shear stresses are occurring during engine break-in. The first hours of use are grueling due to the initial mating and wearing of parts. Oil evaluations on brand new engines can be misleading (as member LubeDude has displayed).<br /><br />An objective person would also have to consider how the engine was "broken-in". Pulling skiers with a brand new engine above the recommended rpm range would undoubtedly put abnormal stresses on the oil.<br /><br />But it doesn't matter, the used oil analysis concluded that for the new engine,
all looked normal.<br /><br />I'll also point out that the post member LubeDude referenced is over 2-years old, and would not include the newest NMMA certified semi-synthetic Mercruiser 25W-40 oils that are currently being used. <br /> <br />Regardless, you may want to brush up with the API's viscosity-grade read across standards. It would not be uncommon for a 25W-40 oil to exhibit properties of a 30 weight oil. Especially since the Mercruiser oil does not contain viscosity improvers and it is a Newtonian oil (the viscosity does not change with the rate of flow like non-Newtonian oils with viscosity improvers).
