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What Brand of Oil and Filters Should You Use on Your Boat?

Brand Awareness

motor oil

Should you buy your oil and filters from the same company that built your engines?

Boaters are not generally considered to be tight-fisted—actually, let me rephrase that. Powerboaters are not generally considered to be tightfisted. We all know how successful sailors are at stretching a dollar until George turns blue.

Powerboaters, on the other hand, are acclimated to spending money, and that is especially true when it comes to the maintenance of their boats. We may all bemoan the fact that anything labeled “For Marine Use” is automatically half again as expensive, but we also recognize the fact that the marine environment is uniquely stressful on gear and that things that were designed for use on land often don’t endure on the water.

So, bemoan though we may, we generally accept the necessity of paying more for products designed specifically for our boats. Yet there is one place where powerboaters often balk at paying extra and that is in the engine room. They question whether it is necessary to pay extra for oil, filters, and other components from an engine manufacturer when apparently identical products are available at an often considerably lower price. This is especially true of oil and filters.

The suspicion often is exacerbated by the vaguely threatening verbiage in your owner’s manual that reads: “Use only [engine manufacturer’s name here] oil and filters or their approved equivalents.” Well, how do you know what qualifies as an approved equivalent?

Let’s concentrate on oil first. Do you need to pay extra for CAT Oil or Quicksilver etc. when you can buy seemingly good oil at a big-box store for half the price? More to the point, will using one of those alternatives jeopardize your engine or, worse, void your warranty?

To answer that, you need to start with the API rating. The American Petroleum Institute establishes minimum performance standards for all motor oils, which are accepted by engine manufacturers. These ratings consist of an initial letter indicating whether the oil is approved for gasoline (S) or diesel (C) engines, followed by another letter, and sometimes a number, indicating the generation of the oil’s additive package. For instance, the most advanced additive package available is in oils designated SN for four-cycle gasoline engines and CJ-4 for diesels. As the second letter progresses from A, the oil’s formulation is newer and more advanced. Some oils are approved for gasoline and diesel engines so they carry both designations. 

The details of the API ratings are not as important for our purposes as knowing that you should always use an oil with the API rating recommended by your engine manufacturer or higher, and that this rating guarantees the oil meets minimum performance standards. That means that using such oil will fulfill the engine manufacturer’s lubrication requirements for your engine, which by implication also means that using it will fulfill the requirements of your warranty.

So obviously then, it makes sense to buy the cheapest oil that carries the appropriate rating for your engine, right? Not necessarily. The key here is the fact that the API rating guarantees minimum standards. It is quite possible that there are oils available—perhaps from your engine manufacturer—that exceed these performance standards. They could, for instance, contain additives that reduce wear or decrease friction or improve cold starting or any number of things. The operative word here is “could” because there is no way for you or me to determine what extra ingredients are in these oils and what their real value is. The formulation is, in short, a secret. Still, could spending that extra money actually translate into longer engine life? Maybe is the best we can say.

So where does that leave you? Mainly, with these two conclusions: First, as long as you use an oil with the proper API performance classification you won’t damage your engine or void your warranty; second, if you want to make sure you’re using the very best oil available for your engine going with the branded oil from your engine manufacturer makes sense. Whichever course you choose, don’t forget about the other crucial component of oil: viscosity. Using the correct viscosity is just as important as the performance rating when it comes to the health of your engine and validity of your warranty.

What about filters? Should you pay extra for branded versions? Alas, here there’s no independent rating to assure what you’re buying meets minimum standards. To be realistic, millions of motorists and boaters buy filters from Fram, Wix, etc., with no apparent ill effects, and my experience is that engine manufacturers are lenient when it comes to their customers using a filter from an alternative supplier. So if you’re using the correct oil and change it at the recommended intervals and you want to save a few bucks, you’re probably safe with any well-known brand of oil filter.

But then I’m reminded of a mechanic friend of mine who constantly mocks my attempts at economy with, “You spend thousands on a boat and then more money on gear and electronics, and you’re worried about saving a few bucks on a filter?”

This article originally appeared in the August 2015 issue of Power & Motoryacht magazine.