Gas mix ratio for Stihl MS 390

Kenster Posted By Kenster, Feb 22, 2013 at 9:37 AM

  1. Kenster

    Kenster
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    I was about to go fill up my chain saw gas can and I put in two 2.6 ounce oil bottles. I then realized that one bottle was 1:40 and the other was 1:50. I don't have any more right now.
    How can I adjust the amount of gas to be able to use this? Is there a drastic difference in the two types of oil?
    Should I just dump it and start over?

    Thanks!
     
  2. Bigg_Redd

    Bigg_Redd
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    What is the ratio in the can right now? Between 40:1 and 50:1? If so, use it up. Your saw will never know.
     
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  3. Kenster

    Kenster
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    The two gallon can was empty. I put in one each of the two kinds of oil and I'm now in town about to put two gallons of premium gas in the can. Sounds like it won't hurt to have a mix of 40:1 and 50:1.
    Good to know.
    Thanks!
     
  4. TreePointer

    TreePointer
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    2.6 oz. bottles are for making one gallon. So if you poured both bottles into two gallons, then it is as Bigg_Redd stated-- somewhere between 40- and 50-to-one.

    If you poured both into one gallon, then it's somewhere between 20- and 25-to-one.
     
  5. Researcher1

    Researcher1
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    put in 2 gallons and it won't make any difference.
     
  6. wh401

    wh401
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    You'd have a 50:1 mix no matter what type of oil it is. Oil itself isn't the mix ratio, the amount of oil mixed with the total amount of gasoline is. So, two 2.6 bottles of oil in two gallons of gasoline would be 50:1 no matter how you do the math. So your good.:)
     
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  7. TreePointer

    TreePointer
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    Good point. Kenster, are you sure that 40:1 bottle isn't a 3.2 oz. bottle?
     
  8. Sean McGillicuddy

    Sean McGillicuddy
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    So when do you put the gas stabilizer in?
     
  9. TreePointer

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  10. BobUrban

    BobUrban
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    I am guessing you have one oil bottle that is 2.6oz. (50:1) and one that is 3.2oz. (40:1) I have the same thing because I could not get the 2.6 one time. Just run it - no problems and better to run a little on the rich side than the lean anyway.

    As mentioned, most quality 2 stroke oil has gas stabilizer in it but I add Stabil marine grade(green stuff) to my larger gas cans before I go to the pump. Just a little insurance as this gas goes into all my toys and not all are 2 cycle.

    Your saw is safe.
     
  11. mikefrommaine

    mikefrommaine
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    1 gallon is 128 ounces. It's all math from there.

    (128*2)/(2.6+3.2) =44.137

    If you want your final mix to be 50:1 add 2.03125 gallons of gas to 5.2 ounces of oil.

    Or 2.26 gallons to 5.8 oz if that's what you already put in the can. (for 50:1)
    Or 1.8125 gallons to 5.8 oz for 40:1

    Not gonna make a big difference as everyone else pointed out.
     
  12. ScotO

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    I buy my 2-cycle oil by the quart or gallon, and it's easy to measure out with one of these.......

    [​IMG]

    It's called a Ratio Rite measuring cup. Made specifically for measuring out 2 cycle oil (it has both metric and standard graduations on it). I use it for my snowmobiles, my saws, my weedeaters, my leafblowers, etc. Comes in really handy, especially when mixing up a 5 gallon gas can.........
     
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  13. Kenster

    Kenster
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    Pointer, you raised a good question so I went out and pull the bottles out of the trash. The bottles are exactly the same size but one is labeled 2.6 oz and the other is 3.2 oz. Both for one gallon of gas
     
  14. EatenByLimestone

    EatenByLimestone
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    I always run 40 to 1. It doesn't hurt to run a bit too much oil. My plug stays clean too.

    Some of my equipment specifies 50 to 1, some 40 to 1. It's easier to run only one mix.

    Matt
     
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  15. bogydave

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    Clicked on the Amsoil ad at the bottom.
    Couldn't find any 2 cycle oil for mixing chain saw gasoline?
    What gives?
     
  16. TreePointer

    TreePointer
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  17. bogydave

    bogydave
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    What I meant was
    No small bottles for 1 gallon or 2 gallon of gasoline, so I don't have to measure.

    Ever try to measure 2.6 oz or 3.2 oz of 2 cycle oil with the wife's measuring cups ?
    Hard to be accurate & even worse if you get caught. :eek:

    Alway wonder how much stays in the measuring cup.
    How long will it drip as you wait to get it all out?

    I like the small bottles so I can add some gasoline, shake & add it to the jug.
    That way I think I get it all & have a good mix ;)
     
  18. ScotO

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    Why not save 5 or ten of those little bottles, and get a gallon jug to refill all of them......makes it even easier than the ratio rite!
     
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  19. mikefrommaine

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    I use an old self measuring stabil bottle. Makes for quick measuring at the gas station.

    Heres another
     
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  20. bogydave

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    Thought of that.
    How to get an exact measure to refill the bottles?

    Maybe a big syringe .

    Hey, (light bulb) that got me thinking
    I have some big syringes somewhere in the shop. (from the old oil & water sampling days)
    >>>>>............
    Back, Found one. 2oz/ 60 ml
    This should work & be pretty accurate.

    DSCF0652.JPG DSCF0654.JPG

    Thanks Scott ! !
     
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  21. ScotO

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    That'd be perfect, BD!
     
  22. mikefrommaine

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    I have a few hundred of those in the basement, use them all the time in the garage. Great for wood glue too. Though Once you put oil or PB blaster in them they don't work very smoothly for long.
     
  23. Boog

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    I saved two little 3 oz Stihl bottles that had the old style clear strip down the side. I don't see those around any more. I just refill them with 2.6 oz from a hoard of pints I bought long ago.
     
  24. bogydave

    bogydave
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    Lets see if I got this right.

    I mix in 1 gallon jugs .
    128 / x = 50 / 1
    50x =128
    x = 128 / 50
    x =2.56

    I'll save the small 2 cycle oil bottles & re-fill them.
    & save some with a gallon of good synthetic.
    I'll be set for a while.

    2.7 oz wouldn't' hurt
    I usually put .9 gallon in the jug & rinse the small bottle with gas to get it all.

    All that said.
    Now?
    What's the consensus on what is "the best 2 cycle oil" for chain saws?

    DSCF0659.JPG

    I got 6 of the 2.6 oz bottles when I bought the Stihl blower,
    $15.54 for 6 pack of 2.6 oz bottles.
    $2.59 for 2.6 oz.
    $1.00 per oz. :oops:
    $32.00 per quart_g
    $128 per gallon :eek:



    Definitely time to start refilling the small bottles.

    The Amsoil INTERCEPTOR 2-Cycle Oil, synthetic is only $40 a gallon/
     
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