Old Gas

[Moneyshot]

Have some gas left in boat from last October. I honestly cannot remember if I treated it (stabilizer) or not. It likely does have some quickcare and quickleen in it.

I know the sure answer is drain it, but getting rid of 20ish gallon of fuel is easier said than done from a storage perspective, especially when you have a diesel truck another car with a full tank and only need cans for weedeater, blower, and push mower.

What about the option of topping it off with another 20-25 gal of fresh fuel?

What are the risks?

*I intend to change plugs either way

[barbarian]

Admitted non-expert advice. I’d put 15 gallons of fresh high octane and go on a long run and try and burn 1/2-3/4 tank and get it down to 1/8 of tank or less and treat the left over.

[bware]

I think you’ll be ok, especially if the boat is is a garage. I put my boat away in early November till April or so every year for over 25 years. Most every year I did put in Stabil but not always. I do use non-oxy almost exclusively. I would add some Startron or Seafoam, add a few gallons on fresh gas, maybe replace or drain the water separating fuel filter, and it should be fine.

[RMG63]

I work for a major oil company ... our lab says gasoline starts to degrade after 30 days (lose octane). There are some variables that accelerate this process or lessen it, such as where you live, also if it has ethanol blended in it or non-ethanol gasoline. Non-ethanol is far the best to have in your scenario.
After about 90 days all the additives required to meet EPA standards etc etc begin to "seperate" and starts to varnish (gum up). Sta-Bil, Techron, Mercury additives to help from the process from happening faster. These are not "snake oils", they truly work and should always be in your fuel regardless of how long the gasoline is stored.
Adding fresh fuel to "stale" gasoline does help, HOWEVER, it is unlikely to break down all the varnish/gumming in your old fuel.
If you run your engine doing this, I would be prepared to change your fuel filters AT MINIMUM.

Hope this helps, its not a guarantee but kind of a guideline

[Highcentered]

I work for a major oil company ... our lab says gasoline starts to degrade after 30 days (lose octane). There are some variables that accelerate this process or lessen it, such as where you live, also if it has ethanol blended in it or non-ethanol gasoline. Non-ethanol is far the best to have in your scenario.
After about 90 days all the additives required to meet EPA standards etc etc begin to "seperate" and starts to varnish (gum up). Sta-Bil, Techron, Mercury additives to help from the process from happening faster. These are not "snake oils", they truly work and should always be in your fuel regardless of how long the gasoline is stored.
Adding fresh fuel to "stale" gasoline does help, HOWEVER, it is unlikely to break down all the varnish/gumming in your old fuel.
If you run your engine doing this, I would be prepared to change your fuel filters AT MINIMUM.

Hope this helps, its not a guarantee but kind of a guideline

This is what I've heard as well. I also use Stabil Marine 360 in the 87 e10 that goes in my boat and mowers. It works and is cheap insurance.

[Moneyshot]

Wish it was a little easier to pump it out but I can't come up with a reasonable solution

[McQuaig]

Wish it was a little easier to pump it out but I can't come up with a reasonable solution

Every year I remove all gas from my tanks for winter storage. On mine it's very easy...I remove the fuel sender unit (5 screws) and siphon it out into gas cans sitting on garage floor. Just a cheap $10 plastic siphon, give it a few hand pumps and then it self-drains while I have a cold one. I use the gas in other things thru winter.
siphon.jpg

[Moneyshot]

The act of draining isn't the issue, it is the storage. I have 20+ gallon

[99R93S]

I would ask RMG63 if he knows does exposure to oxygen make a difference? Example would half a can of fuel be as degenerated after 90 days as a full can with no oxygen exposure. I’ve heard/read it makes a difference.

[McQuaig]

The act of draining isn't the issue, it is the storage. I have 20+ gallon

I use it in snowblower, mower, chainsaw...anything that I don't care so much about octane level after sitting for a few months...

[Dave A]

Add some seafoam and go run that old gas out.

[Rangerdeepv]

Couple bottles of seafoam and run it like you stole it. Always put the Merc products in every fill up.

[RNKingCx19]

New gas mixed in it….Seafoam as said above Run it

[mactlman]

get a bottle of Lucas fuel conditioner and top off with fresh fuel

[reelswift]

Would it be possible take a sample and have it tested for octane and or damage causing properties ?

[old4runner]

I use it in snowblower, mower, chainsaw...anything that I don't care so much about octane level after sitting for a few months...

I use last years boat gas (50:1) in the mower all the time. She smokes a little but no issues at all.

[billius]

I always use Stabil 360, every time I put gas in the boat. When I think I'm done with the boat for the winter I fill the tanks and double the dose of Stabil. Its always good to go in late March or early April. I've done it that way for more years than I can remember.

[rchavis]

I just did this. Didn't want to chance it. Walmart has a nice siphon pump.
If your tanks are in the back of the boat.
I jack the boat up on the opposite side and just ,went thru the fill tank hose.
Worked good for me.
Just slow. But that good for me as I had only to 5 gals gas tanks. I removed 24 gals.

[RMG63]

I would ask RMG63 if he knows does exposure to oxygen make a difference? Example would half a can of fuel be as degenerated after 90 days as a full can with no oxygen exposure. I’ve heard/read it makes a difference.

Tony,
My understanding of oxygen exposure is that it obviously increases evaporation but I would have to ask our Lab techs this question for more of a reliable response. I would think that adding the fuel stabilizers would slow down oxidation but I'm not completely sure on that one.
I will ask tomorrow

[Moneyshot]

Added seafoam, 15 gal of high octane, quick care n quick kleen and ran it. Missed a little under load for on the first run but ran well after that.