5 Best 4-Stroke Boat Engine Oils (Reviews Updated 2022)

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Boat engine oil is composed of a variety of lubricants which act to maintain the function of a boats engine. The oil allows all of the different mechanisms of the engine to run smoothly and prevents damage from occurring. Boat engine oil differs to regular vehicle oil and has been specifically tested to make sure it is appropriate for marine use. 4-stroke boat engine oil is specifically for use in 2 stroke engines.

Best 4 Stroke Boat Engine Oil

Here are our 4 stroke boat engine oil reviews.

1. Quicksilver 4-Stroke Marine Engine Oil SAE 25W-40

Quicksilver 4 Stroke Marine Engine Oil Sae 25w 40

The Quicksilver 4-Stroke Marine Engine Oil SAE-25W-40 is is a premium 4 stroke engine oil for boats. This oil is great value for money and is made by the reputable Quicksilver. It promotes a healthy boat engine.

  • Low emission composition
  • No-ash oil fights rust deposits
  • Combats spark plug fouling and sticking rings
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2. Mercury 4-Stroke Engine Oil

Mercury 4 Stroke Engine Oil

The Mercury 4-Stroke Engine Oil is an oil which works to promote the maximum performance of a 2-stroke boat engine. This engine 4 stroke boat oil is affordable, and performs under extreme weather conditions.

  • No ash formula minimizes piston ring sticking
  • For use in all oil injection or pre mix 4 stroke boat engines
  • Low emission clean oil
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3. Quicksilver 8m0078622 4-Stroke Marine Engine Oil

Quicksilver 8m0078622 4 Stroke Marine Engine Oil

The Quicksilver 8m0078622 4-Stroke Marine Engine Oil is a 4 stroke boat engine oil of the highest quality. It is made to prevent carbon deposits from harming the performance of a boats engine. This oil provides protection to the piston tops and under crowns.

  • Guards against harmful build ups in the engine
  • Keeps marine engine running clean
  • Promotes longevity
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4. Sierra 25W40 Oil

Sierra 25w40 Oil

The Sierra 25W40 Oil is a reliable 2-stroke boat engine oil. This product is designed to minimize the wear and tear on an engine. It therefore helps to promote long engine life. All sierra products are backed by their leading warranty.

  • NMMA TC-W3 certified product
  • Enhances engines performance
  • Minimizes combustion chamber deposits
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5. Yamaha Yamalube 4M Outboard FC-W Four Stroke Engine Oil

Yamaha Yamalube 4m Outboard Fc W Four Stroke Engine Oil

The Yamaha Yamalube 4M Outboard FC-W Four Stroke Engine Oil is high performance 4-stroke boat engine oil. Made by the reputable Yamaha, this oil is one of the best quality and value in its class. It is specifically made for use in marine engines only.

  • NMMA TC-W3 high quality formula
  • Anti-wear and corrosion protection
  • Guards against carbon build up
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4 Stroke Boat Engine Oil Buyer’s Guide

Choosing high quality 4-stroke boat engine oil is a wise investment for a boat owner. A relatively low priced-item, engine oil could be mistaken as not being important. In terms of maintaining the good condition of the engine, it is actually a very important item. The wear and tear of a functioning boat engine and the metals rubbing together will inevitable cause damage over time. Engine oil prevents this damage from happening.

Our buying guide reviews the best 4-stroke boat engine oil on the market so you can choose the right oil for your engine. Following are some common features of 4-stroke boat engine oil to look out for when considering which one to purchase.


The viscosity of 4-stroke boat engine oil is the measurement of how easily oil pours at specific temperature. The lower the viscosity number is, the thinner the oil. This will result in easier pouring than a 4-stroke boat engine oil which has a high viscosity number; however these oils are more effective at maintaining strength of film and pressure at higher temperatures.


4-stroke boat engine oil is the type of product which you apply periodically when the need arises. Generally, applying the oil once or twice per year will be enough. This can vary depending on the amount of mileage you will travel on your boat, which may mean you require more regular application. Getting good value by checking the amount of oil you will get for your money is a good idea. A good bottle of engine oil should last you a long time if you purchase a significant amount.


Boat engine oils are compatible with different engine types. Some will be suited to, for example, applications above 75HP. Other oils will be compatible specifically with 4-Stroke while others will be universal.