Merc 20W40 Full Syntnetic Oil Discontinued ??

jason78

jason78

Active Member
TECHNICAL Contributor
Sep 3, 2008
3,662
Fort Mill, SC / Lake Wylie
Boat Info
1997 20 Outrage
Engines
200 Merc Offshore
I was gathering some pricing information this morning to post something in another oil related thread. Went to Merten Marine website who typically has the best pricing on oil. I immediately noticed that it looks like Mercury has changed their product line a bit. According to what they [Merten] have on their site, Mercury Full Synthetic 20W-40 is no longer available. Apparently it has been replaced with the Synthetic Blend 8M0078629. Looks like they have also introduced a 10W-30 Mercury branded oil as well with this change.

Any Merc dealers (Dennis) have any insight as to why they have apparently reverted back to synthetic blend as the "top" recommended oil? It seems like synthetic blend has been discussed here before and the general consensus what that it was not a good idea to use it due to shearing or something like that (don't recall exactly). It would be nice to know if there is a good technical reason they made the change to the product offering or of this was simply a contract problem or something of the sort with their OEM supplier agreement for the Full Syn.

http://www.mertenmarine.com/servlet/the-Mercury-Oil/Categories



Does not look like Mercury has updated their own website yet though-

http://www.mercurymarine.com/servic...ntenance/faqs/mercruiser/?category=fuel#MCOil
 
Since this new synthetic blend appears to be universally approved for older and newer catalytic engines, I fear this is a business decision to minimize sku's. I question whether this new synthetic blend protects non catalytic engines as well as the previous synthetic blend. Yes, I distrust large corporations motives in these scenarios.
I'm sure the marketing people will spin it to their advantage.
 
I have always run synthetic blend, I noticed the packaging was different this fall. Didn't really think much of it at the time. Interesting, if running full synthetic I would be disappointed in full synthetic no longer being available.
 
Yes, the full synthetic has been discontinued. I do not know the real reason and I do not know if there are any plans to introduce a new synthetic, or not. The semi-synthetic has been reformulated to work in the catalytic-equipped engines and the outboards (and of course the older engines). There used to be a separate oil for the 4-stroke outboards.
 
The 25-40 is still available, as far as I know. I just checked on my online Merc parts lookup and it's in stock at Mercury. If there are plans to discontinue it I have not heard of that, yet.
 
I have always used the Merc Dino 25W-40 but know plenty of people who will not be happy with the discontinuation of the Full Synthetic. I don't know all the ins and outs but I have read in numerous places that once you go to Full Synthetic you should not go back. I guess people will have to decide whether to go back to Syn blend or go with a Full Synthetic automotive oil that does not carry the FC-W marine rating. I am wondering if Merc switched to a new (cheaper) OEM supplier who is not capable of producing the full Synthetic.
 
I started using Amsoil 10w-40 in my 496 two seasons ago and have been very happy. I used the merc 25w-40 up to that point and wanted to switch to synthetic. One of my reasons for going to Amsoil over merc full synthetic was that I actually paid less money for it delivered to my door.
 
I ran into this issue a couple months ago when I tried to get full synthetic for my winterization oil change, and couldn't get it. I too will be switching to Amsoil next time. I have used Amsoil part #RD50 in my Mustang for many years, and have been very happy with the oil analysis results from that, so that's my choice for my 8.1s in the 340. RD50 is a high performance 15w-50 full synthetic oil, and its performance in my Mustang's 575hp stroker, as well as the test results I have reviewed for this oil, have all been very positive.

Your best bet is to do your research, consider the style of boating you do, what engines you have in your boat, and the climate in your area, then make your decision.

Dale
 
I don't use synthetic, but not because I think it's bad oil (actually, I do use it in my truck, but thinking of changing back)... far from it. So I won't say to someone "don't use it". Besides, my opinion on synthetic is not the point of this post and I'm not trying to sway anyone one way or the other. I was simply looking at that Amsoil link you posted, Scott, and I saw this and thought it was interesting (actually "surprising" was probably more like it):

"Inboard and I/O applications: Change oil at two times the engine manufacturer recommended interval or one year, whichever comes first." Does this mean you are now changing your oil every 50 hours or twice a season?

Jason - I've heard about the "switching back to dino oil" thing, too. I have yet to find any credible information on that, though. I am not an oil expert, but I honestly find it hard to believe that it would cause a problem. In fact, any synthetic I have used in the past (or read about) says it is OK to mix their synthetic with regular. Of course they say that it "diminishes the benefits of the synthetic", but if you can mix it I'm sure it's OK to go back. Even if it wasn't OK to mix, a full oil change or two and it should be pretty much completely out - or at least to the point where it doesn't matter. I dunno - just my thoughts on it! :smt001
 
I used to race superbikes an flattrack 8 yrs ago. Alisyn lubricants was a sponsor of mine and I learned alot about oil. People worry more about what goes in their engine than the cheap beer or liquor while sitting at the dock. Just my 2 cents. Used this oil for 6 plus years and also used it in my semis, which was against my fathers recommendation. Rotella T is gold to him. So after running a motor at daytona with approximately 10 races and spinning @ 17k rpm no wear o provide r loss in HP. So with the motors on the lake all synthetics are man made from a receipe. Thats why its more. Great oil so in my semis fuel mileage went up a mpg which is great. Here is the link not trying to get in a debate just putting out some info! The company started out in the marine industry out of TX, and they provide the grease to the beer companies can assembly line.
 
One comment and then one question, if I may.

I did a LOT of research on synthetics and semi-synthetic blends a few years ago for automotive applications. I don't know the specifics on the Mercury synthetic blend, but be aware that there is no industry standard specification for what makes a "blend". We read that term and think that means it is a 50/50% dino oil / synthetic mixture. Nope, it could be 95% dino and 5% synthetic.... there's no way to know. A lot of oil companies jumped on this bandwagon when they found a great way to raise the price of their dino oil by adding a little synthetic into it and calling it a blend. If I wanted a blend, I'd buy dino and synthetic and mix the stuff 50/50 myself. It would cost the same as a blend and I'd know it really was 50/50. If anyone here knows for a fact what the Mercury blend is please let us know. It could be 50/50; all I am saying is that I don't take that as a given.

Finally, a question: I do plan to go to Amsoil but wonder if there is any appreciable difference in 10w-40 and the recommended 25w-40 weight for these marine engines. I assume not, but wanted to hear from others if anyone knows.
 
I have been using Amsoil products in everything I own for about 20 years. It is great stuff. You can't go wrong using it IMO. I had an old BMW in college that had 150k miles on it when I bought it and I sold it 6 years later with 278k miles and it didn't burn a drop of oil between changes.
 
IMO, 10W-30 is a bit too thin at operating temperatures for Mercruiser engines, especially the older 8.1 engines! That's why the manufacturer recommends 25W-40. In fact, Mercury recommends straight weight 40 in an emergency when that's all you can find (summer use).

In Order of Preference - Info Provided by Mercury Marine:

1. Best: Mercury/Quicksilver 25W-40 Synthetic Blend, NMMA FC-W-rated 4-cycle MerCruiser oil
2. Good: Mercury/Quicksilver 25W-40, NMMA FC-W-rated 4-cycle MerCruiser oil
3. Fair/Good: Other recognized brands of NMMA FC-W-rated 4-cycle oils (closest to 25W-40 weight like 10W-40)
4. Emergency: A good-grade, straight-weight detergent automotive oil according to the last row of the operating chart below.
-Summer (50 Degrees or Higher): Straight Weight 40
-Fall/Spring (Above Freezing): Straight Weight 30
-Winter (below Freezing): Straight Weight 20

Remember, the first number is the viscosity of the oil when cold, and the second number is the viscosity of the oil when hot.

Interesting Video - Don't Destroy Your Engine With Bad Motor Oil
https://youtu.be/FXdaitlxzGM
 
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Working from my old memory, so use at your own risk.

Motorcycle oil versus car oil... usually car oil contains Molybdenum, also called moly. It's a metallic lubricant for high pressure. Unfortunately, most motorcycles have a wet clutch and moly and wet clutches don't get along, you can end up with excessive slipping in the clutch. So most motorcycle oil has to be reformulated to get lubrication without the moly.

Going from Syn back to Dino, I always heard it the other way was not supposed to be done. This was because in the early days of the likes of the original Mobil 1, it had a lot of detergent properties. If you had a high milage engine, the sludge would build up on the inside and keep oil from keeping the inside butt of the seals wet. When you used a high cleaning oil, the sludge could not only become dislodged and then possibly block a critical path, but it could also suddenly cause oil to be against an old, dried out seal... and then the leaks started. Today I'm told, full syn doesn't clean like it used to so people don't have to worry as much about using it in a high milage, dirty engine... but I still wouldn't try it.

My biggest issue with dino oil... If you remember back a few years ago, Pennzoil ran commercials about how they had the purest base stock and then said, it's 97% pure. That means you're starting with 3% garbage in your oil. And here's what is bad about that... your oil is one of your primary coolants... that means it gets to the hottest places in the engine. That 3% carbon has the potential to coke up as it works as a coolant, become very abrasive and cause wear. Full synthetic oil is 100% pure and you start with at least 3% less garbage in your fresh oil... so it lasts longer.

The other nice thing about Synthetic oil is that you can naturally design it from the start to have a wider viscosity range as it goes from cold to hot. With dino oil, you add in a lot of viscosity modifiers. These are long chained organic molecules that if I remember correctly, wind up tight when cold and unwind when hot, I believe to make the oil less viscous at hot temperatures? Unfortunately, these molecules get broken in time and your oil viscosity is no longer what it was.

Oh, another thing, oxidative stability... remember the mobile one commercial, oil in a frying pan? In high heat situations (what's your first coolant?) syn is much more resistant to oxidizing and becoming sludge.

But a final warning... wear a good glove, go to a good tool supply place and get good oil resistant disposable gloves. I was recently talking to someone that has bladder cancer. It's believed he biggest risk in their life was the occasional motor oil changing... he was a long term user of full syn oil, wore not gloves and tells me that it's believed the stuff absorbed through your skin pretty well. Now I've always worn gloves because I can get a reaction from used motor oil and always thought that was my enemy... but even clean syn, probably should wear gloves.
 
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