Always love a spirited conversation about oils, but here is why some things need detergent and some don't. Keep in mind this is not an all inclusive story about the virtues of oils, but a practical one to use as a guideline. Detergent in oil helps to keep dirt and foreign particles in suspension so that they may be removed by a screen or filter. They are also responsible for combating the ill effects of the internal combustion engines byproducts that combine with other elements such as water to form acids and sludge. This has a beneficial effect of keeping engines with pressurized oiling systems happy and clean. Now items that deal with higher pressures(Hydraulics) or have high speed rotating assemblies tend to need no detergent oil for one main reason, foaming. Some hydraulic oils have small amounts or modified detergents but not like motor oil does. Best advice, use the type and rating of oil that is suggested by the manufacturer and all is well. As for the trim pumps on my boats, I use 30w non detergent oil for the reasons listed above. If your not certain what's in it, then its time to replace it to be certain. Hope this helps, Michael.
