What type oil should I use in my outboard? Verified

[LubeDude]

This FAQ Article may not answer all of your questions, as it is written for general information and not meant to be technical. No oils are said to be better than others, nor any effort made to settle the question about which brand or type is "best". There is no agreement on that.<br /><br />If your engine is a carbureted or EFI water cooled 2 stroke you should use an oil that is certified TC-W3 by NMMA, with the mix ratio recommended by the engine manufacturer. Outboard oils are sent to the NMMA, National Marine Manufactures Association, for TC-W3 testing. The term TC-W3 means: Two Cycle, Water cooled, spec. number 3.<br /><br />The tests include varied bench tests for fluidity, lubricity, viscosity, etc., plus the oil must meet minimum standards for ring sticking and carbon build-up on pistons in engine tests. The chemical make-up of the TC-W3® oils vary due to the various additive packages involved with each oil brand. Accordingly, it's a performance based qualifications program. The process is very involved and expensive, but worth the outcome for consumers and manufacturers.<br /><br />Outboard engines are characterized by their constant speed, high output operation. They are usually set at a desired high speed and continue at that speed until the destination is reached and then throttled down. Also, they are constantly cooled with fresh, cool, non-re-circulated water. Water-cooled, two-stroke engine oils require high levels of a heavy oil to prevent piston and cylinder wall scuffing. Because of their high average piston temperature, lighter oils evaporate too quickly from the piston cylinder contact area. The heavy base oil, which vaporizes at very high temperatures, resists evaporation and remains in place to provide lubrication to the piston and cylinder. <br /><br />Some feel you should use the oils from the manufacturer of the engine in question. You cant go wrong with this practice. Also if you have an engine that is still on warantee and you have any problems, the whole thing may go easier if you are using their product. However, they cannot void your warantee if you are using a TC-W3 certified oil, unless the warrantee specifies requirements for a non-TC-W3 oil.<br /><br />There are many TC-W3 oils to choose from, It seems every oil company has one and then some. So, which one do you choose? Ultimatly this decision will be yours to make. The purpose of this article is not to recommend one product over another. The iboats archives offer a wealth of arguments and information but no answer on the question of which brand is best.<br /><br />All TC-W3 oils are not created equal however. Some have more additives than others. I do not think that it is possible today to buy a really bad oil. <br /><br />TC-W3 is a ten year old Specification, and outboards are changing all the time. A few new technology engines demand different formulations. We may someday see a TC-W4, or ?.<br /><br />Some Direct Injected (DFI) 2 stroke outboards require oil specially formulated for those DFI engines. Owners should use any oil "required" in warranty limitations, though not necessarily those "recommended". Some DFI engine failures have been attributed to use of oil that was not up to the published requirement for those DFI engines.<br /><br />There are a few other outboard engines for which TC-W3 oil is not suitable. <br /><br />Air cooled outboards should use oil intended for air cooled engines, chain saw oil or "Weed Eater" oils, for example. These oils are formulated for the higher temperatures air cooled engines run.<br /><br />Four stroke outboards are a whole different story. Again, users should stay within the limits set by the warranty. Automotive oils are generally suitable, but some oils are offered as "4 Stroke Outboard Engine Oil".<br /><br />Now, What about synthetics?<br /><br />There have been many discussions about this subject, and some of them heated, but I think the majority agree that there are benefits from using the synthetics or synthetic blends (mixed with petroleum based oils), but are not sure if the benefits outweigh the cost.<br /><br />So what are the benefits the manufactures claim?:<br /><br />Superior performance in DFI outboard motors <br />Prevents piston and combustion chamber deposits <br />Prevents "ring jacking" common to DFI outboards <br />Low smoke, low odor product <br />Prevents wear for long engine life <br />Prevents rust <br />Low aquatic toxicity<br /><br />Here is their explanation for the benefits claimed:<br /><br />100% SYNTHETIC OUTBOARD 2-CYCLE OlL contains only ashless components which is said to prevent any lubricant related preignition and spark plug fouling. The ashless additives also help protect against piston and combustion chamber deposits, rust and corrosion. It resists gel formation due to water or other contamination. The special base stocks used help protect the engine against piston and cylinder wall scuffing.<br /><br />We now have a new oil out from one manufacture for older "seasoned" outboards that is a synthetic blend. <br /><br />Here is what they say about it.<br /><br />Developed for engines that are seasoned or have been in service for a few years. However, the robust formulation makes this oil exceptionally applicable for new high displacement/horsepower carbureted or direct injection outboard motors. Uniquely formulated with extra ashless dispersants to help keep performance robbing carbon deposits from forming in the combustion chamber, piston tops, under crowns, and piston combustion rings. Most importantly it helps keep exhaust ports clean. Formulated to a higher lubricity limit than NMMA AF-27 lubricity test to provide EXCELLENT protection against piston scuffing and reduce wear.<br /><br />Advertizing claims seem to never end.<br /><br />Many here on the forum use one synthetic or another, either a blend or a full synthetic. There are several with the TC-W3 certification. Most say they are getting the benefits claimed, but some have gone back to regular TC-W3 for various reasons.<br /><br />There are concerns that synthetics used at recommended leaner ratios do not protect well enough in the off season due to less oil coating of corrosion vulnerable parts, but it is hard to test corrosion in a real world application. In the end, its solely up to you whether you want to use it or not! Some swear by it, and some swear at it.