Cold weather gasoline

First, summer time gasoline is not as volatile as winter gasoline. So if by some strange chance you've got gasoline in the tank that was put there in July, it's doing its best to simulate grease and not evaporate for combustion in the cylinders. It makes starting quite tough, and is a major factor in why snowblowers that ran fine when tested in the summer refuse to start in the winter.

Second, don't put high test in there. Yea, it sounds neat to "put a tiger in the tank" and such. But it doesn't work. High octane gasoline is less volatile then low test. That's why it doesn't knock in high compression engines. But this also means high test is closer to being kerosene then low test gasoline is. Ever try to start a kerosene engine on kerosene? Which means that high test is harder to start, especially if its cold.

So, winter gas, and low octane for the winter cold.

• Gasoline discussion on tool talk forum

The volatility specifications (distillation, vapor pressure, V/L, drivability index) for all grades of automotive gasoline are the same for a given season. These specifications do change from season to season (summer to winter), so all gasolines are more volatile in the winter (to improve cold starting), and less volatile in the summer (to prevent vapor lock).

The difference between grades of gasoline is the octane rating, which is the number you see posted on the pump. Due to the nature of high octane molecules compared to low octane molecules, premium gasoline tends to be more dense than regular gasoline. The low compression engines in the N series tractors should not experience pinging on regular gasoline, so buying premium for a N is a waste of money.

AvGas is designed for aircraft engines, and the specs are different than for automotive gasoline. AvGas is generally expensive, assuming you can find it. An N tractor should not need AvGas to run properly.

From a gasoline standpoint, the main thing to do to help the tractor start in the winter is to buy gasoline for the tractor during the winter. Do not use gasoline that's left over from summer (or even early fall, for that matter). If you have fresh gasoline in the tank and you still have problems starting, the solution likely is somewhere other than the gasoline.