Oops - added the wrong oil to 2-Stroke outboard tank

[denverd0n]

Back in the old days, there was no such thing as special oil just for 2-stroke engines. We always just mixed a little motor oil into the gas, and things worked fine. Yes, it might smoke a bit more than usual, but you are not going to do any permanent damage to your engine.


Personally, I would just run it and not worry. Next time, though, be a little more careful.


Good luck.

[Zanshin]

Thanks for all the responses. Just as with my Google searches, the ones here were varied. As I would have had to schlepp the 25l canister a good 2Km to the yard, I opted to add 500ml of good 2-stroke oil to canister. Once it is emptied a bit I'll think it out with pure fuel. I'll post my results to this thread, perhaps including a picture of the plugs after this tank has been used.
I did get a private note from someone who has had contact with a current Yamaha 2-Stroke engine engineer. The gist was that since the majority of sales were to 3rd world markets, design fuel and oil quality would be assumed to be very bad, and the engines are designed to ingest just about anything and keep running. So, I'm not as worried as I was yesterday, considering I'll only do this once for about one tank of fuel. But I have learned my lesson!

[NorthCoastJoe]

I would drain it and start fresh. The old mix could be run in an old carb type large engine, such as a V8 or old tractor.
I would be leary of running it in a modern Fuel Injected engine, or anything with small ports. If it were me at home I would dump it into my 1960's farm tractor, that is how I use my stale 2 stroke mix.

[RaymondR]

It's not going to be a problem Zanshin, the extra lubricity might even make it run better.

[David Mathis]

A few years ago I watched a three month old six cylinder Mercury being disassembled after making "weird" noises then not running. The dealer found a couple quart containers of 10-40 in the boat and asked the owner about them. He claimed that the TCW oil was way too expensive, a rip-off, and the discount store brand oil was just as good if not better. The repair was not covered under warranty.


Dispose of the improperly mixed fuel and replace it with some that is properly mixed with TCW-3 oil. We complain abut the price of fuel but it's cheap when compared to an engine rebuild.

[sck5]

If you just run the motor with that oil, be sure you have some carb cleaner around. You will need it

[argonauta1]

No worries! Us old guys remember when there was no outboard oil to add, just SAE 30. If you are worried, add a bit of your outboard oil to the mix and press on.

[RossD]

While growing up, I had an old Mercury from the 40s, and at some point moved to a '58 Evinrude, both utilized on my small fishing boat. We did not have access to special oils most of the time, so regular four-stroke oils were commonly utilized. Never an issue, but yes, a tad smokier.

[BBill]

Run with the added oil and don't worry about it. You and motor will never know the difference...other than more smoke with the additional oil. Running 6 gals won't clog up anything. Years back OB ratios were down to 16:1 with 30w motor oil. OMC came up to 100:1 in the 1980s and went back to 50:1 ONLY to prevent corrosion during storage. They specified actual lube needed at idle was 300:1 and 150 at full throttle. Autolube systems were richened at lowest idle at shut down just to coat the internals for storage. Most of this info came from the past warranty manager for OMC International. He was over South America, Bahamas and Bermuda. He was a cruising on a Colvin Ketch before going to OMC and could be lurking.

[Zanshin]

I've used about a quarter of a tank now. The engine starts on the first pull every time. It runs with little or no smoke, even cold at idle. It sounds good and I checked one of the two plugs yesterday: clean with no evident discoloration.

So far, so good!

[LakeSuperior]

Originally Posted by Zanshin

I've used about a quarter of a tank now. The engine starts on the first pull every time. It runs with little or no smoke, even cold at idle. It sounds good and I checked one of the two plugs yesterday: clean with no evident discoloration.

So far, so good!

No surprise here!

[GrowleyMonster]

If you can get proper two stroke oil, then get rid of what you got. No, it PROBABLY won't hurt your engine to burn up that tankful of what you got, but why put it to the test, when you can pour out, discard, and start fresh? If it happens in the middle of nowhere then only use the engine if you absolutely have to, until you can change out your fuel/oil mix. I have burned small amounts of old gasoline or mixed gas and 2 stroke oil, in the car, and no harm no foul. Talking a quart or two at a time in a full tank of gas. Likewise you COULD save and dilute, adding two stroke oil as others suggest, but I think I would regard it as false economy. Whichever way you go, it probably won't destroy your outboard and I know it is not unheard of, to use 4 stroke engine oil in place of 2 stroke oil, but I have never heard of anyone making a habit of it and I do believe that would probably end badly, eventually. Short term? Minor risk. Do you want minor risk, or operation as per the owner's manual and manufacturer's direction?

[Nicholson58]

Originally Posted by Zanshin

I just filled my outboard tank with 25 liters of fuel and mistakenly added 500ml of 10W-40 motor oil for a 50:1 ratio mix. I'm in the Caribbean (St. Lucia)

I am looking at 3 options:

1. Dump it at a local boatyard and start again
2. Use as is and expect some fouling on the plugs and dirty exhaust
3. Add 500ml of good 2-stroke oil to make a 25:1 ratio, which is what Tohatsu recommends for breaking in the 18HP 2-Stroke that I have
4. ??? open to suggestions ???

Do #1
WD40 is NOT oil. It will no lubricate. It may wreck the machine if you run it.

[Zanshin]

@Nicholson58 - where was WD-40 mentioned? Certainly not by me.

I added correct 2-stroke oil to make a 25:1 mix and have it running very well. Once it is 1/2 full, I'll further dilute it with fresh gasoline and 2-stroke. As reported, no issues. Of course, I can't speak to the long-term effects but not one of my Caribbean 2-Stroke outboards lasted more than 8 years before being either stolen, sold, or dying from having gone diving while running so I'm not too worried about absolute longevity here.

[Bill_Giles]

I have an ancient Mariner (just like me then). It gets any oil that comes to hand. It seems pleased with that. But I would not recommend it for anything else.