Farmall Cub

What Octane Gas is best for 48 cub. I will be using Old Nellie this winter for snow plowing. and thought that higher Octane
would be better. (been using 86 octane) Thanks Johnny

I have always run plain old regular gas in mine and never had any problems.

Regular unleaded 87 octane is what I use in Ellie come summer or winter. Thankfully I don't have to deal with ethanol

edited: fixed a boo-boo

Higher octane fuel is for engines that have a compression ratio much higher than our Cub powerplant.

Hitnmissman wrote:Higher octane fuel is for engines that have a compression ratio much higher than our Cub powerplant.

Right. You can actually lose horsepower by running higher octane fuel because it probably won't burn completely in the Cub combustion chambers. As a rule of thumb, you should run the lowest octane fuel that doesn't pre-ignite (ping) in the combustion chamber. You shouldn't have a problem with this in the low compression engine of a Cub.

I'm not sure if any Cubs were set up this way, but some of the old tractors of this era were started on gas and switched over to kerosene after they warmed up. So low octane is what you want to use.

Most everyone uses regular unleaded 87 oct. The old tractors of the era were really designed to run on 72 octane gas? Called in the old days tractor fuel. Cubs were too.But gas today is not like it use to be. If i were useing my cub to work a lot I would use 90 oct or better. from working on engines which used 87 I found alot of carbon deposits. ( plugged up) with 90 oct or better they run pretty clean much less build up of carbon.

Clark,

I'm certainly no expert on fuels, but I believe the lead they used to put in the fuel also contributed to carbon buildup in engines. I believe it also increased the gumming up of carbs and other gas exposed items much more than the gas we use today. However, with the ethanol now being added to gas there are other downsides. Has anyone noticed how the plastic fuel lines on small 2 cycle engines just seem to rot away in no time? In the old days, I recall my Dad always insisted on using "white" gas (lead free) in the old Wisconsin air cooled farm engines, believing it would reduce carbon up on the rings.

I think I agree with Challenger's dad. I used to use white gas in airplanes for that reason. Don't know if true or not but I sure felt better and always got home. I also used diesel (from road machines) in a '42 Willis sedan when in high school. Couldn't afford 22 cents/gal for gas.
Reg

I like 89 octane anyway

AND, please add 2oz of Marvel Mystery oil to five gallons.

I agree also. I am no expert in fuels either but I have had engines apart that used the cheap unleaded gas of today for many years. The lower the octane gas seems to build up a lot of carbon deposits on valves and in the exhust ports. I have had apart cubs that were only run on high octane (93), One cub was mine.There was hardly and carbon build up and the plugs foweled much less.I beleive the the higher octan gas burns a lot cleaner but also has more detergents added to aid in the valve train being kept clean.Now the old tractor fuel 73 octane really caused probems.Burnt a lot of valves.