A reader asks: I’ve got twin 2013 Mercury MerCruiser 8.2L H.0. MAG inboard engines in my boat. This engine does not show up in the AMSOIL application guide. Can you recommend an AMSOIL motor oil and oil filter for this engine?

Our answer: While it’s true that MerCruiser engines are not included in the “Marine” section of AMSOIL’s online application guide (for some reason), we can provide a couple of motor oil options as well as an oil filter recommendation for your 8.2L H.O. MAG engines.

Engine Oil Options

AMSOIL Synthetic-Blend 25W-40 Marine OilThe first option we would suggest is AMSOIL’s brand new Synthetic-Blend 25W-40 Marine Oil. This motor oil was engineered specifically for Mercury/MerCruiser motors. Marine engines are routinely put under tremendous strain and this new 25W-40 is designed to provide consistent and long-lasting wear protection. This AMSOIL 25W-40 is a cost-effective upgrade for Mercury Synthetic-Blend SAE 25W-40 Marine Engine Oil.

If you would prefer a 100% synthetic option, have a look at AMSOIL 10W-40 4-Stroke Marine Synthetic Motor Oil. This 10W-40 is a highly suitable replacement for any 25W-40 marine oil. It offers all of the wear control, shear stability and extreme heat resistance required for your MerCruiser engines in a high-tech, full-synthetic package. If you want a full-synthetic oil over a semi-syn for your engine, this is your best bet.

Does AMSOIL Offer A Full-Synthetic 25W-40?

AMSOIL offers only the synthetic-blend 25W-40. Mercury markets only a semi-synthetic 25W-40 for their engines, so AMSOIL wanted to provide a product that was easily recognized as a Mercury alternative. There is absolutely no technical reason to use only a synthetic blend in these engines. We’re quite sure that Mercury did this to keep motor oil input costs down. Prior to the release of this new AMSOIL semi-synthetic 25W-40, AMSOIL suggested the 100% synthetic 10W-40 4-Stroke Marine Synthetic Motor Oil for all Mercury applications requiring 25W-40 motor oil. The 10W-40 is an outstanding shear-stable option, but as Mercury owners were looking for 25W-40 and were unsure about a 10W-40 (despite the fact that it is an outstanding substitute), AMSOIL created the new 25W-40.

The bottom line is that either option is perfectly fine. Have a look at our pricing and choose from there.

Oil Filter For MerCruiser 8.2L H.O. Engine

The oil filter that is compatible with your Mercruiser 8.2L H.O. engines is the AMSOIL EAO-59. The AMSOIL EAO oil filter line is robust, durable and among the most efficient on the market. AMSOIL EAO Oil Filters are built with superb components making them a great match for your MerCruisers.

We can provide oil and filters at wholesale prices for your Mercruiser engine in both Canada and the United States. Contact us for pricing information using the form on this page of call us at 1-800-748-5781. 

AMSOIL Synthetic-Blend 25W-40 Marine OilAMSOIL has released a brand new 25W-40 4-stroke marine engine oil for Mercury engines and we have it available for immediate delivery. The new AMSOIL Synthetic-Blend 25W-40 Marine Oil (product code: WCM) will be suitable for any Mercury Marine outboard, stern drive or inboard engine that requires a 25W-40 motor oil. This new 25W-40 meets the NMMA “FC-W Catalyst Compatible” specification, but is also suitable for engines that are not equipped with a catalyst.

Why Did AMSOIL Make A 25W-40?

In the past, AMSOIL had suggested their Synthetic 10W-40 Marine Motor Oil for Mercury and Mercruiser engines that required 25W-40 oil. As we explained in this article, AMSOIL’s 10W-40 Synthetic Marine Oil is a highly capable and safe option that can easily replace Mercury 25W-40. The problem is that many consumers simply will not consider a 10W-40 product when they are looking for a 25W-40. This is especially true if they have warranty concerns. A 25W-40 would be the quick and safe choice for busy consumers, so it only makes sense for AMSOIL to have a Mercury-specific 25W-40 ready to go.

Why A Semi-Synthetic 25W-40?

With AMSOIL being almost exclusively a synthetic oil company, why would this product be a synthetic-blend? Mercury Marine owner’s manuals specifically suggest the use of only semi-synthetic 25W-40 motor oil for many of their engines. To alleviate any warranty concerns, AMSOIL opted to make this product a semi-synthetic.

Mercury does not specify why a full synthetic oil is not suitable for their engines and frankly we don’t believe that there is a legitimate reason. We don’t know of any application where a full synthetic oil would be anything but a benefit. Our suspicion is that Mercury felt that a synthetic-blend oil would be an adequate product that met a reasonable price point. We don’t think there is a justifiable mechanical reason behind this logic.

AMSOIL’s Technical Department has always suggested a full synthetic oil for Mercury Marine engines. But in the case of this new 25W-40, rather than reinvent the wheel for consumers, they felt that a high-quality semi-synthetic 25W-40 oil would provide great service and be a viable choice for the average Mercury engine oil shopper.

Features and Benefits Of AMSOIL Synthetic-Blend 25W-40 Marine Oil

  • Robust anti-wear protection
  • Powerful anti-rust and corrosion protection
  • Suitable for catalyst and non-catalyst equipped engines
  • Outstanding shear resistance
  • Does not contain viscosity index improvers
  • Protects during heavy loads and high operating temps

How Is AMSOIL Synthetic-Blend 25W-40 Marine Oil Priced?

AMSOIL has priced this new 25W-40 priced similarly to the OEM Mercury Synthetic-Blend SAE 25W-40 Marine Engine Oil. We will submit that AMSOIL made a point of making a superior oil too. Check out our wholesale buying options for individuals or businesses. Request a wholesale price list with the form on this page and see how our high quality products are a great value.

Where to Buy How to Buy AMSOIL Synthetic-Blend 25W-40 Marine Oil? can ship this new 25W-40 for Mercury Marine engines from Mississauga in Eastern Canada and Edmonton in Western Canada. We also ship from 11 warehouses in the United States. We can have a case of this new oil on your doorstep in just a day or two.

Can This New 25W-40 Be Used In Flat Tappet Cam Engines?

We would not suggest this new 25W-40 for older Mercruiser engines with flat tappet cam shafts. Some older Mercruiser engines such as the 5.7L (350 c.i.) produced by General Motors had flat tappet camshafts. Flat tappet cams require an engine oil with very high zinc levels. As this new 25W-40 oil is suitable for engines with catalytic converters, it will not have the zinc levels needed. High zinc levels are not compatible with catalytic converters. We offer a motor oil suggestion for flat tappet cam Mercruiser engines in this article.

The same logic applies to automotive motor oils. The latest passenger car motor oils do not contain enough zinc to protect older engines with flat tappet cams.

Other Oils Replaced By AMSOIL Synthetic-Blend 25W-40 Marine Oil

AMSOIL Synthetic-Blend 25W-40 Marine Oil is a high-quality substitute for the following marine engine oils.

  • Mercury Synthetic-Blend SAE 25W-40 Marine Engine Oil
  • Quicksilver 25W-40 4-Stroke Synthetic Blend Marine Engine Oil
  • Quicksilver 25W-40 4-Stroke Mineral Marine Engine Oil
  • Bel-Ray Marine 4-Stroke 25W-40 Engine Oil
  • Cabela’s Signature Semi-Synthetic 25W-40 4-Cycle Oil
  • Lucas Stern Drive 25W-40 Inboard Engine Oil
  • Sierra 25W-40 Premium Blend 4-Stroke Marine Oil
  • Sierra 25W-40 Synthetic Blend 4-Stroke Marine Oil
  • Sierra 25W-40 Premium Blend Catalyst Compatible 4-Stroke Marine Oil
  • Starbrite Premium Synthetic Blend 25W-40 4-Stroke Engine Oil
  • West Marine Premium 4-Stroke Synthetic Blend 25W-40 Outboard Oil

Update May 2016: We now offer a 25W-40 oil for Mercury Marine engines.

Update: If you have a Mercruiser engine with flat tappet cams, read this.

If you are looking for a high-quality replacement for Mercury or Quicksilver 25W-40 engine oil in your MerCruiser stern drive or inboard engine, we have the ultimate substitute. AMSOIL 10W-40 Formula 4-Stroke Marine Synthetic Motor Oil replaces all all conventional, semi-synthetic and synthetic 25W-40 marine engine oil formulas. Read more