How Long Can Gasoline Sit in a Motorcycle? (Answered!)

Motorcycle gas tank

A motorcycle gas tank is not a great storage place for gasoline. The tank exists to supply fuel to the engine.

If the gasoline sits in the motorcycle tank for too long, it will degrade in quality.

So how long can gasoline sit in a motorcycle? Gasoline sitting idle in a motorcycle gas tank deteriorates by 6 months. The quality degradation starts by 30 days.

So, drain out old gas if it is sitting idle for months.

And use fresh gasoline for your motorcycle.

Gasoline shelf life in a motorcycle tank

Gasoline sitting idle in a motorcycle gas tank starts becoming less combustible after a month and deteriorates by 6 months.

So, if the gas in your motorcycle tank is 6 months old, don’t use it.

To be cautious, I would say even 3 months of idle time is bad.

Don’t use the stored gasoline in the tank if the motorcycle is staying idle for more than three months.

The gasoline quality would have deteriorated by then.

There will be varnish. Slime formation. Water absorbed by the gas. And overall – poor quality, low-combustible gasoline remains in the motorcycle tank.

The simple solution is to – flush the old gasoline in the tank. And pour in fresh gas.

Flushing out the old gasoline

Getting rid of the old gasoline from your motorcycle tank is quite simple.

Take a pan or container. You need it to collect the old gas.

Locate the fuel pipe. It goes from the fuel tank – through the reserve fuel switch – to the carburetor.

Motorcycle fuel pipe

Make sure to turn the fuel switch to the OFF position first.

Now, disconnect the fuel pipe from its carburetor end.

Place the container below the fuel pipe to collect the old gasoline.

Next, turn the fuel valve to the ON position now. And then to the RES to drain the reserve tank as well.

Motorcycle Fuel Valve - RES

Place the fuel pipe above the container and flush out the gasoline completely from the tank.

Once drained, put the fuel pipe back and tighten it.

Pour fresh gasoline into the motorcycle fuel tank now.

A note on gasoline shelf life

Gasoline is obtained from crude oil by processing them in a refinery.

When we say shelf life in this post, we are referring to the gasoline stuck in the motorcycle tank for days. Even months.

The shelf life of crude oil and that of gasoline sitting in a motorcycle are not the same. They are different.

Crude oil lasts long. Gasoline in the motorcycle doesn’t.

Gasoline goes bad only if the motorcycle is kept idle for months.

The motorcycle hasn’t been used for days and months and even a year or two. Only then does the gas quality decline.

Why does gasoline go bad in a motorcycle?

There are several reasons why stagnant gasoline in an idle motorcycle gas tank goes bad.

First reason, gasoline becomes less combustible over time.

Gasoline is a vaporizing fuel. Even though it is stored in the motorcycle tank, the gas starts to vaporize ever so slowly. Mixed with the contamination within the tank, the gas becomes less combustible when it sits in the motorcycle gas tank for months.

Second, the contaminants and deposits intensify.

The motorcycle gas tank is filled with contamination. And with the stagnant gasoline there, mixes with the contaminants and starts forming varnish deposits. Polymer compounds start to form as well.

Third, the ethanol blend in gasoline absorbs water.

The gasoline we use today usually has a 5% to 10% of ethanol blend in it.

The ethanol blend absorbs moisture and condensed water present in the tank and fuel pipe easily. This water absorption again makes the gasoline less combustible.

How to check if the gas is bad

Identifying bad-quality gasoline is pretty easy.

One can easily see deteriorated gasoline based on its color, texture, appearance, and deposit formation.

Here is how you can check:

  • Color: Gasoline will be clear in color with a yellow, red, or green tinge. But bad quality gasoline will have intensified red or brown color. It won’t be clear as well.
  • Appearance: The gasoline must have a transparent appearance. If the gas is no more transparent and has a frothy, non-clear texture – then gasoline has gone bad.
  • Gums and deposits: The gasoline must be free of any gums and deposit formation. But the gasoline sitting in the gas tank for months will have gums and varnish formation that can be clearly seen.

What if you run the bike with bad gasoline

Running a motorcycle with bad fuel can be detrimental to motorcycle health. Especially the engine components.

If you ride a motorcycle with bad and deteriorated quality gasoline – the engine components get affected. And might even get damaged as well as the worst scenario.

The affected parts include all the engine components.

The combustion chamber, piston, piston rings, intake valve, carburetor, fuel injector valve – all these parts might get damaged.

So, it’s better to get rid of the old gasoline. And ride the motorcycle with fresh fuel.

Does the motorcycle start with old gas?

If you have kept the motorcycle idle and let it sit for months, and the gasoline has sat in the gas tank, there might be starting problems.

But the starting problems might not necessarily be because of the low-quality gasoline.

Even with deteriorated gasoline, the motorcycle can start.

So yes. The motorcycle will start with old gas.

Is it recommended though?

Nope. It’s better to drain the old gas. And pour in fresh gasoline to start the motorcycle.

Can you use additives to keep the gasoline fresh?

While additives help, they don’t prolong the gasoline life considerably and won’t keep the gas fresh in the motorcycle.

Make no mistake. Additives are helpful.

Lots of additives are used in gasoline.

While there are several gasoline additives that help in preventing deposit formation, decreasing gums, preventing oxidation, etc., prolonging gasoline shelf life is still difficult.

So, to keep the gasoline fresh in a motorcycle tank for months – additives are not of much help.

Can you mix old gas with new gas?

Mixing old and new fuel is a big no-no.

You should not mix the old deteriorated gasoline with the new and fresh gasoline.

That defeats the entire purpose of using the new gas.

If the old gas has sat idle for months, always drain the old gas completely.

Only once you have drained the old gas from the motorcycle tank, pour the new gasoline into the tank.

The old gas would be of low quality, less combustible, and contains gums and varnish deposits. So, don’t mix it with the new gas.