Well, according to this thread:<br /><br />Mercruser 25W-40<br /><br />Dello 400 15W-40<br /><br />Dello 400 30W<br /><br />Wallmart SuperTech 30W<br /><br />Amsoil Diesel Marine 15W-40<br /><br />Pennzoil Long Life.<br /><br />And all oils in between!!<br /><br />SH, SJ, CF-2, CF-4 etc.<br /><br />25W-40, 20W-50, 10W30, 10W40, 15W40, 30W, 40W.<br /><br />Racing oil, Diesel oil, car oil, Marine oil.<br /><br />Regular oil, Synthetic blend, 100% Synthetic oil.<br /><br />What are you suppose to use? 25W-40, 30W, 40W, CF-2. Diesel Marine.<br /><br />Whats the best? THATS A JOKE, RIGHT???
Called my local repair shop (no boat sales, just repair and parts), http://www.drydockboat.com , and they have the new semi-synthetic 25W40 for inboards and sterndrives.<br /><br />He said they just got it in a week ago. Using the Oct 11 date above, they must have overnighted it to my repair shop the next day
.<br /><br />Price is $5.10 for quarts and $14.25 a gallon.<br /><br />Quart price is high, but the gallon price is not that much more than the Merc dino at ~$10 a gallon.<br /><br />Still no change in Merc's web site. Anyone want to place a guess on when they will change their "recommendations" to include their own oil? LOL - I crack myself up.<br /><br />I still have to decide whether I go with the Merc semi-synthetic at winterization oil change or whether I will "go out on the edge" and use Royal Purple SAE 40.<br /><br />Too many oils, so few boats......These types of discussions often lead to unnecessary confusion. <br /><br />Your question is one that can be answered by simply following your Mercruiser's specification. <br /><br />The real question is, "How do we justify using an oil that is not specified by the manufacturer?".<br /><br />The only way to do this is to accept anecdotal opinions and off-the-cuff claims that can't be substantiated. We must accept the fact that recommendations are unsupported. We must ignore decades of Mercruiser oil and engine testing, simple concepts of oil technology, recommendations from the oil makers themselves, and specifications established by the API, SAE, and ASTM. We must replace the notion of which oil works best, for the notion of which oil works. We must convince ourselves that we know more than the professionals.<br /><br />The choice to use, or not use, any one of the recommended oils for your Mercruiser is up to you. 10 of the 14 Mercruiser owners in this topic are using the correct specified oil (including myself).<br /><br />The correct way to establish what oil is better for the Mercruiser is not through oil reports. It is through measuring actual engine wear.
Uh, which one? The one on the Merc semi-synthetic bottle that says use this great new oil, or the one on the web that says specifically, no synthetics? <br /><br />
To me, the question is, "How can you possibly take Mercury seriously?" With Volvo recommending a synthetic with the same GM block and Mercruiser not recommending a synthetic until they come out with one, what are we listening to, decades of Mercruiser testing and engineering or Mercruiser marketing?<br /><br />What do you think the new Mecruiser recommendations are going to be regarding synthetics that aren't their own? My instinct tells me that there is an internal debate within Mercury as to what the new recommendations should state: "use our new semi-synthetic, and we recommend against using any other synthetic", or "use our new semi-synthetic, and if not available use synthetics meeting x, y, z, criteria"?<br /><br />If they do the former, they loose credibility. If the state the latter, they lose profits. To me, it will be very interesting what the new recommendation identifies as acceptable oils.<br /><br />After my last UOA that contained close to 7% fuel dilution in 53 hours, I am convinced that the 100 hour, once a season synthetic oil change is out for me. I think I am going to be better off using an SAE 40 dino and changing every 25 hours.<br /><br />For me, I guess I am part of the four of Doc's 14 that won't bow down to recommendations based on marketing. I prefer to do my homework, and use Merc's marketing recommendations as a guideline. I then perform UOA's and let the analysis for my oil tell me what is best for my engine and my boating habits. So far, I'm not impressed with the VOA or UOA of the Merc 25W40 dino oil in my boat.
No. An oil analysis is a great way to keep an eye on your engine. But OA's are generally used to predict maintenance intervals and identify internal engine problems. Their results are not necessarily a reflection of good or bad oil. They are a reflection of the condition of the engine. Many variables can effect what is in an oil sample (change intervals, ambient conditions, environmental conditions, consistent load and rpm, good baseline, fuel, prior engine history, etc.). <br /><br />To legitimately claim what oil is "best" for your Mercruiser you would need to measure actual part wear. For an oil to carry the CF,CF-2/SH (SL) Mercruiser specification, it must pass a host of tests which evaluate engine parts.<br /><br />As one example: In order for an oil to become Mercruiser CF,CF-2/SH (SL) rated it must pass ASTM D 5119 (Sequence L38 test). This is a consistent, controlled test. It uses an established test engine. The engine is run for 40 hours at 3150 rpm with an external oil heater keeping the oil at 290'F. After the run the engine is disassembled. Connecting rod bearing weight loss is measured. The engine and parts are inspected and rated by trained professionals using special methods. The oil undergoes a 10-hour stripped shear stability test. It must stay in grade. Another test ASTM D 5844 inspects the engine's push rods, valve lifters, and oil pump relief valves. <br /><br />Even the nmmas procedure for evaluating outboard oils includes disassembly and measurement of engine parts on established test engines. The oil is not evaluated. The engine is.<br /><br />Using industry-established methods and inspecting post-test engine components is required to legitimately evaluate lubricants. <br /><br />Most OA's will not provide all critical shear properties needed to evaluate the oils ability. Evaluating oils based on Mercruiser OA comparisons that dont exist, nor explain the shear properties, would not be legitimate. We can only take opinions for what they are.<br /><br /><br />
Mercruiser has already answered your question as referenced by member lakelivin in a prior post:<br /><br />Mercury has just recently developed a 25W-40 synthetic blend oil that we are recommending in our latest engines. This oil was not available when your engine was built. If you choose to use a synthetic oil, this one is the only one we recommend.<br /><br />It appears Mercruiser is not comfortable making a blanket statement that any synthetic oil is ok for their engine. There may be some synthetics on the market that are not compatible with some Mercruisers, or Mercruiser may have done some testing that showed some synthetics with certain viscosities and additives are not the best for marine use. Clearly Mercruiser has developed a new oil that they recommend for their latest engines, and your engine. If you can find this oil available, it would meet specification.<br /><br />I have also addressed your question several times. Engine manufacturers do not go back and revise engine specifications on older engines each time a new oil category or oil technology is approved. New oil specifications or technology do not drive engine technology. Engine technology drives oil technology. You can never go wrong using oil that was originally specified for your engine. You can never go wrong using oil that has been improved and includes the specification originally recommended by the manufacturer.<br /><br />Choosing an oil for your Mercruiser isn't as hard as you are making it.
Mercruiser's CF and CF-2 specifications are the latest and most current oil technology. Mercruiser's SH specification is included in the latest SL oil technology. Mercruiser isn't prescribing 20 year old medicine.<br /><br />Because an oil is "synthetic" does not mean it automatically meets the engine's specification. For example: The Mobil 1 15W-50 does not carry the CF-2 Mercruiser spec (plus it is a non-specified viscosity). This is like the doctor prescribing Ex-Lax for a headache. The CF-2 category places specific and unique requirements on the oil as tested per ASTM. Using an oil without this spec would be like ignoring the doctor's prescription all together.<br /><br />
Mercruiser does not test each and every oil on the market. They test their engines under a variety of API category standards (CF, CF-2, SJ etc.) to determine which class of oil is best for their engine. However, they are aware that there are some oils on the market that may not be compatible or optimal for their engine. These may be synthetics carrying solid additives, or additives which are not suitable for their engine's marine environment. There may be a compatibility issue with a part. Blanket statements recommending "synthetic" oil may not be best. <br /><br />
Mercruiser owners are not obligated to purchase Mercruiser brand oils. They are not obligated to run synthetic. Their engine oil specifications leave an array of brand opportunities. Where synthetics are concerned, Mercruiser has apparently come up with a semi-synthetic formula that they feel is optimal and compatible with their engines in the marine environment. A blend of straight grade conventional oils and straight grade synthetic oils. I respect that Mercruiser knows what their engines need.
<br /><br />Buttanic:<br />Ratfish:<br />JimmyTheKid:<br /><br />Thats allright, Im not buying all the Mercury knows best stuff either, Ill just leave it at that.
Put Mercruiser aside. Even big oil makers like Shell (Rotella), Chevron (Delo 400), Mobil (15W-50 syn) don't recommend the oils you are for marine use.<br /><br />Shell recommends their straight grade Rotella T. Chevron recommends their Delo 100. Mobil recommends their Mobilgard. Very different oils with very different characteristics.<br /><br />The API has come up with special categories for these oils. Stringent ASTM engine tests were developed specifically for them.<br /><br />Separating out the anecdotal information and opinion, it would appear not all oils are the same. Certain oils are developed for certain uses. Otherwise there would be no need to classify oils at all, and one oil would work on all engines in all environments. <br /><br />Could you take the time to explain to members why they should disregard the manufacturer's specifications (viscosity, API category, etc.), the oil maker's recommendations, the API's service categories, and the standards and testing established by the ASME, SAE, etc.<br /><br />I am particularly interested in any technical information that would support your recommendations.
.<br /><br />I picked up two gallons of the Mercruiser sterndrive synthetic blend today. I'll use it in a few weeks for my winterization. I'll send off a sample for a VOA.<br /><br />The thing that cracked me up about the oil and this thread was that there are NO API categories listed on the label.<br /><br />No idea whether this is a group III, IV, or V oil, what percentage is synthetic or what API categories it meets (if any at all).<br /><br />But, the label says that "we" have tested it and it is good for your engine .
