Which gas to use on old brush cutter.

4xMF · Jul 17, 2021

I just bought an old McCulloch Super Mac 26 brush cutter. I use Aspen alkylate 2 stroke gas in all of my other small gas powered equipment and it is a 2 percent oilmix. I dont know how old the McCulloch is but I suspect it is older than the introduction of said environment friendly gas and as I recall it my old chain saw called for a 4 percent mix. I have also had a Chinese made brush cutter seize caused by too little oil I suspect. So now I have these questions:
1. Can I run it on the alkylate gas as it is with no worries?
2. Should I use it and add an extra 2 percent 2 stroke oil?
3. Should I use regular gas which has 5 or 10 percent ethylene
in it and add 4 percent 2 stroke oil?
I have tried to download a users manual for the machine but the PDF wont load.

glennster · Jul 17, 2021

try 20 to 1 and see how it goes. a lot of the old 2 cycles ran
that ratio.

Dean · Jul 17, 2021

Prior to 20:1 mix, most 2 cycle engines used 16:1 mix. Don't know what your Mac is designed to use.

In any event, I would avoid gasoline with ethanol at all costs.

Dean

guido · Jul 17, 2021

4xMF,

I WOULD USE AT LEAST 5%. If it's totally smokeless at all speeds, I would go to 6%

Guido.

Russ from MN · Jul 17, 2021

I mix everything 3 oz. to the gallon of ethanol-free 91 octane, that's about 43 to 1, for all air cooled 2-strokes, regardless of age. My
oldest chainsaw is 49 years old, it works just fine. The oil now is so much better than what was available 40 years ago you don't need so
much.

Bret4207 · Jul 18, 2021

Those date from the late 80's to early '90's. Likely intended to run at 40-1 or so. I would use a non-ethanol bearing gas and mix at 40-1. Thats 25ml of oil to 1 liter since I see you're in Denmark. Be aware the fuel lines, filter and carb may need attention and repair.

4xMF · Jul 18, 2021

(quoted from post at 07:25:55 07/18/21)

Those date from the late 80's to early '90's. Likely intended to run at 40-1 or so. I would use a non-ethanol bearing gas and mix at 40-1. Thats 25ml of oil to 1 liter since I see you're in Denmark. Be aware the fuel lines, filter and carb may need attention and repair.

Thanks for all the replies and for this information in particular. I didn't know it is that old. So I'd better add some oil to that premix. This little machine starts and runs like new. I don't think it has been used much. I am going to put a small chain saw head on it for trimming trees with branches hanging down scratching the cab on my tractor. I have a fairly new Echo for the heavy work.

Bret4207 · Jul 19, 2021

(quoted from post at 18:04:22 07/18/21)

(quoted from post at 07:25:55 07/18/21)

Those date from the late 80's to early '90's. Likely intended to run at 40-1 or so. I would use a non-ethanol bearing gas and mix at 40-1. Thats 25ml of oil to 1 liter since I see you're in Denmark. Be aware the fuel lines, filter and carb may need attention and repair.

Click to expand...

Thanks for all the replies and for this information in particular. I didn't know it is that old. So I'd better add some oil to that premix. This little machine starts and runs like new. I don't think it has been used much. I am going to put a small chain saw head on it for trimming trees with branches hanging down scratching the cab on my tractor. I have a fairly new Echo for the heavy work.

HA! When I read the opening post and you said "old Mcculloch" I was thinking an OLD Mcculloch from the 60's! :lol:

Which gas to use on old brush cutter.

4xMF

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glennster

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Dean

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guido

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Russ from MN

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Bret4207

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4xMF

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Bret4207

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