2-stroke gas/oil mixture ratio

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Xland

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I have an older Craftsman chainsaw that says it needs 16:1 mixture ratio, is that still valid with today's 2-stroke oils? It seems that today's 2-strokers have 40:1 or 50:1 ratios. The richest mixtures I have seen 32:1.

I just used it for the first time in a very long time, using the stated ratio and it smoked like crazy. Ran fine, but with a blue cloud! I do not remember it being quite so smoky long ago, in a galaxy far, far away.

How risky is it to reduce the amount of oil I mix? It is an old saw, but I do not want to ruin it. It is a great tool when needed!
 
Two cycle oil has gotten much better, therefore you can run a leaner mixture now. If it were me I'd try 40:1.
 
Hisilver is right on target -- 40:1 is current recommendation for Craftsman.

Pick up a bottle of Trufuel 40:1 from your local retailer (Lowes, Home Depot, etc.)

trufuel-40-1.jpg
 
What oil are you currently using?

Today's oil are a bit more concentrated and contain more AW additives and better base oils. I had an old chainsaw from the late 50's that specified a 32:1 ratio and it ran fine with little smoke.

Remove the muffler and check the muffler port for deposits and cylinder finish for any scratches.

If there are no gummy deposits, then try and adjusting he mixture screws.

If there are port deposits, try a ratio of 32:1 and see if it still smokes.

Also try a new sparkplug.
 
Last edited:
Originally Posted By: hisilver
Two cycle oil has gotten much better, therefore you can run a leaner mixture now. If it were me I'd try 40:1.
I thought 40:1 is richer. Oil displaces fuel causing lean condition?
 
Originally Posted By: Xland
I have an older Craftsman chainsaw that says it needs 16:1 mixture ratio, is that still valid with today's 2-stroke oils? It seems that today's 2-strokers have 40:1 or 50:1 ratios. The richest mixtures I have seen 32:1.

I just used it for the first time in a very long time, using the stated ratio and it smoked like crazy. Ran fine, but with a blue cloud! I do not remember it being quite so smoky long ago, in a galaxy far, far away.

How risky is it to reduce the amount of oil I mix? It is an old saw, but I do not want to ruin it. It is a great tool when needed!


This must be a pretty old chainsaw. You might consider a newer chain saw for safety reasons. A new saw will be lighter and have a chain brake.
 
32 to 1 has been tested many times to provide sufficient lubrication for all but the most extreme conditions.

However, you do need to know how that engine is constructed. There are certain types of bushings used in older 2 strokes that require a thick fluid film of oil to ensure adequate lubrication. On these engines, more oil is absolutely essential.

If you choose a modern ratio designed for needle and ball bearing engines, the end result will be an egg shaped bushing on the connecting rod, and/or wallowed out crankshaft bushings. This results in crank seal leakage, loss of power and poor operation, as the air finds it's way in.

On some older 2 strokes, the aluminum or magnesium crankcase was actually the bearing surface. Ultra cheap! The connecting rod often has a brass bushing pressed in, but not always. These "cheap" engines really suffer rapid wear without enough oil. See if you can find a parts diagram.
 
Last edited:
Originally Posted By: Cujet
32 to 1 has been tested many times to provide sufficient lubrication for all but the most extreme conditions.

However, you do need to know how that engine is constructed. There are certain types of bushings used in older 2 strokes that require a thick fluid film of oil to ensure adequate lubrication. On these engines, more oil is absolutely essential.

If you choose a modern ratio designed for needle and ball bearing engines, the end result will be an egg shaped bushing on the connecting rod, and/or wallowed out crankshaft bushings. This results in crank seal leakage, loss of power and poor operation, as the air finds it's way in.

On some older 2 strokes, the aluminum or magnesium crankcase was actually the bearing surface. Ultra cheap! The connecting rod often has a brass bushing pressed in, but not always. These "cheap" engines really suffer rapid wear without enough oil. See if you can find a parts diagram.


That is excellent advice and jibes with my experience.
 
Originally Posted By: ARCOgraphite
Originally Posted By: hisilver
Two cycle oil has gotten much better, therefore you can run a leaner mixture now. If it were me I'd try 40:1.
I thought 40:1 is richer. Oil displaces fuel causing lean condition?


No, that ratio represents 40 ounces of gasoline to 1 ounce of 2-cycle oil.

A 16:1 ratio means more 2-cycle oil (richer oil mixture) in the gas.
 
It has a new spark plug, that was the first step after pulling it out of "mothball". I had flushed the carb before its very, very long winter's nap (actually several winters), so the carb should be fine. "should be" is probably the real question.
 
Thanks for all of the comments, helpful indeed.

I have a bottle of Castrol Grand Prix 2-stroke oil, API code TC and exceeds SAE Grade 3. Says it's for injection and pre-mix systems. It has been hanging out for quite a while too - it is not cloudy and no bad smells or residues in the bottle.

It has a new spark plug, that was the first step after pulling it out of "mothball". I had flushed the carb before its very, very long winter's nap (actually several winters), so the carb should be fine. Plus it started right up, we're talking less than 10 pulls.

As for getting a newer saw, not happening right now, this one does not get used much (obviously) and I am unemployed at the moment. Thanks for the tip though. When (if) I get a new one, it will probably be a Stihl.

I think this one was manufactured by Poulan - it is vintage 1984 or so, I am the original owner.
 
Originally Posted By: MolaKule
Originally Posted By: ARCOgraphite
Originally Posted By: hisilver
Two cycle oil has gotten much better, therefore you can run a leaner mixture now. If it were me I'd try 40:1.
I thought 40:1 is richer. Oil displaces fuel causing lean condition?


No, that ratio represents 40 ounces of gasoline to 1 ounce of 2-cycle oil.

A 16:1 ratio means more 2-cycle oil (richer oil mixture) in the gas.
I find this terminology usage incorrect. I don't like a stoichiometric term used for the gas/oil ratio. An old point of confusion amongst 2 stroke owners and bike racers. Having More oil in the mix ratio makes the engine run leaner. Maybe just a peeve of me:)
 
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All the normal stores...Home Depot, Lowes, Ace, TruValue, O'Reilly's, Auto Zone, etc. etc. etc.
 
Originally Posted By: Xland
All the normal stores...Home Depot, Lowes, Ace, TruValue, O'Reilly's, Auto Zone, etc. etc. etc.


Sorry for the delay in response -- just pick up a can of the Trufuel 40:1 mentioned above next time you're at Lowes.
 
Older 2 cycles like LawnBoys, Homelite XL's, and mopeds generally call for a richer mixture, and are safe to run 32:1. I recommend Poulan Synthetic (silver bottle). Walmart carries the 19oz in the garden center.
Gives off less smoke no matter how rich.

Any newer weedeater/chainsaw, be it echo, stihl, etc. Run what the manufacture says, 40:1-50:1, generally. As these newer 2 cycles tend to clog up bad anymore.
 
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