Problem.... 2Stroke oil in my crankcase!

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Euclid537

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Sep 29, 2010
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I changed my oil yesterday, almost 9 quarts of mobil1 0w40.

Tonight when I got home I checked the oil level, just to be safe.. it was only a smidge low, so I grabbed a half-full quart of mobil1 off the shelf in my garage.

As I started to pour, I noticed that the fluid coming out was BLUE! Yikes! Apparently I used a mobil1 quart to mix 2stroke oil some time in the past.

I'd guess that 1/5th to 1/4 of a quart got into my crankcase. The gas mixture is 50:1 if I recall correctly.

My question is this... how bad is this? Is this something that needs to be drained/flushed immediately, or will it not make much of a difference?

I would think that the 2stroke oil must be cleaner than the motor oil because it is introduced into the combustion chamber. And while it may lower the viscosity overall, the dissipation of 1/4 quart within 9 is negligible.

Do you have any thoughts or words of advise? Is this something that I should worry about, and even consider having the vehicle towed to a location where it can be drained?

Thanks so much.
 
Frankly, that small amount, don't worry about it. I just wouldn't go really long.

Entertaining though. I always think about what would happen with say a few quarts.....

EDIT: I READ THIS TO MEAN IT WAS TWO STROKE OIL ITSELF. WAS PREMIX FUEL/OIL ADDED?????
 
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This is about 1/4 qt mixed gasoline for a 2-cycle engine, yes? I'd be a lot more concerned about the gasoline than the smidgen of 2-cycle oil in it. Still- 1 cup of gasoline in 9 qts of Mobil 1 motor oil- it might just "cook out" safely enough- *if* you didn't run it hard for a few hundred miles. Maybe.

If I misunderstood, and it's just 1/4 qt of 2-cycle oil- then I wouldn't worry much about it. I certanly wouldn't have the car towed & drained!
 
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Heck no, leave it in there. It will help with all the extra iron found in all M1 oils
wink.gif
 
Good question....

At startup, your engine gets a lot of fuel, and some of it gets past the rings and enters the oil sump. So a little fuel probably won't hurt it, and will evaporate once you get the oil up to operating temperature. The question is, how much evaporates and how long does it take? I know that in my UOAs Blackstone lists fuel dilution amounts "should be" less than 2%.

IMO you're right about the dilution, that little bit of fluid (1/4 qt, or 8 ounces) into your previous 9 quarts (288 ounces) makes it a little under 3%. Probably ok.
 
I apologize for the vagueness in the original email. To be honest, I don't even remember mixing the oil. It would have been 3+ years ago.

I poured some of the devil-oil into a shot glass to have a better look. It's very dark. Smells slightly of gasoline, but not much. It's almost opaque when held up to a light, which leads me to believe that if it is mixed - it's not much gas.

It has a slight odor of gasoline, but perhaps this is just the smell of 2stroke oil. The color is a dark blue/green.


Pretty funny indeed. Talk about an "oh sh-t" moment.
 
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Originally Posted By: Johnny
If this was pure 2-cycle oil, no problem, drive it.

If this was pre-mixed already with gasoline, I would drain it.


+1
 
Try igniting that shot glass of mystery liquid- maybe pour out a little into an aluminum pie pan or something similar- & see if you think it burns more like gasoline or oil. Also try burning a little *Known* 100% 2C oil for a reference point.

If it *does* burn like gasoline; While the safest thing is to drain it, I still think that with light-load moderate driving- well warmed up but no banzai runs- most of it'll cook out in a few hundred miles. Highway cruising should be ideal. We're talking about 2.78% contamination, for a full 8 oz of gas in 9 qts(288 oz) of fresh M1 oil. Think of a poorly tuned carbureted car with worn rings &/or cyl walls, driven for short hops. After a few months I bet some of those have at least as much gas in a lot less oil than 9 qts.

If it was my car- I'd try the burn test first. If it was mostly gasoline, I'd go for a nice leisurely cruise of at least 1/2 hr a couple of times a week, & not push the OCI too much. If it was just 2C oil, I'd drive normally & run a full OCI on it.
 
You've got, what, a couple of tablespoons of gas in your 9 quarts of oil?

Gawd, forget about it - just run the oil as you usually would.
 
I wouldn't worry about it. You may just have cracked on the code on the ultimate oil/engine cleaner with the 2-cycle oil. Don't be surprise if your vehicle runs cleaner.
 
I would drain it personally. Id bet you didn't have anything to worry about, but for the cost of the change, + the fact your far enough along in your OCI that you're topping up a little, I'd change it out.
 
Originally Posted By: addyguy
You've got, what, a couple of tablespoons of gas in your 9 quarts of oil?

Gawd, forget about it - just run the oil as you usually would.


I think he states roughly a 1/2 pint. That's about 16 tablespoons (or 2 cups).

17.5 pints with about .5 contaminated pint. He's already up to roughly 3% contamination.

Personally, I'd change it. Maybe use it for the mower or something else?
 
To me, it would depend on the type of car and engine, and how old it is. If the car is new, high performance, or expensive, I would change it. If it was a 1980's Ferd or Cheby, I would leave it in.

You might have found the next wonder internal engine cleaner.
 
If I was 100% certain it was only 2 stroke oil with no gas, I'd leave it. If I had the slightest doubt that there might be gas mixed in I'd dump the oil.
 
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