Fuel additive for long term Gasoline storage?

[RichLo]

Hey, I'm going to be getting my 300 gallon farm tank filled soon with non-ethanol 87 octane 'Farm Gas.' I had it filled 4 years ago and I just finally ran out. Back then things were cheaper so I put a gallon of seafoam and a gallon of sta-bil in it when it was initially filled. If I do that again, it'll be over $100 just in additives. The classic tractors were still running fine this year with 4-year old gas although I could tell they weren't as happy under load as they are with fresh gas.

Also, that last fill was summer gas and this will be a winter blend so it'll have a lower flash-point which in-itself may extend the life. The tank has a pressure relief cap so it doesn't just evaporate, it needs to overcome a few PSI or a few in/Hg before it opens to the atmosphere.

Anyway, I'm just wondering if anybody has experience keeping gas volatile for an extended period of time? Should I have added something at 2-years instead of initially?

This mainly applies to my large tank but I am also curious for lesser-run equipment like generators, boats, project cars, etc. This discussion may be useful to others who are considering storing extra gas for emergencies too.

 

[Minn95Dually]

Maybe figure out your run rate and fill accordingly? You can always buy more.

 

[Erik the Awful]

I wonder if it would help to have a bladder in the tank that collapses as the fluid level goes down to keep from oxygenating the fuel? Or at least a floating mat to cover the top of the fuel?

I'd also consider a smaller tank so you only hold the gas two years instead of four.

 

[95burban]

Have you talked to your fuel supplier? They usually carry additives

 

[1998_K1500_Sub]

I wonder if it would help to have a bladder in the tank that collapses as the fluid level goes down to keep from oxygenating the fuel?

Interesting thought… it would also keep the lighter components from getting lost from the fuel to the atmosphere.

With a bladder, I wonder if the fuel might self-fractionalize then, e.g., evaporation / condensation causing the lighter, less dense components to end up deposited atop the liquid and remain stratified.

For comparison: If you pour liquid methanol (density ~80% of water) atop liquid nitromethane (density ~113% of water), in a graduated cylinder or a 5gal jug, they will remain stratified for a long time… they don’t tend to mix themselves, they must be agitated; they do mix easily (both are polar molecules) and won’t stratify in the liquid phase once mixed, but the methanol does like to escape the mix via evaporation.

(edit) Thanking about the gasoline situation a little more, and the example I gave above, I suppose what might happen is the vapor above the liquid would become saturated with the lighter components and that would prevent any further fractionalization… at least, as I believe it could happen.

I’m no ChemE

 

[RichLo]

Maybe figure out your run rate and fill accordingly? You can always buy more.

300 gal minimum for bulk delivery. My tank is actually 325 which is what I just got delivered. Otherwise you pay a bunch more per gallon for a small batch delivery fee.

The bladder or blanket is an interesting idea, but it would be tough to fit a whole floating blanket into a 1" hole on top. And its a horizontal cylinder so surface area changes as the level goes down. I also have a fuel level gauge on the one side that swings with the radius of the tank.

I considered painting it a lighter color so it doesnt heat up as much but I asked about that and they cant fill a liquid tank that is the wrong color. Red for Gasoline, White for Diesel, etc. Maybe I could put a blanket of some kind over the tank to keep it cooler? Then take it off when they deliver.

 

[RichLo]

Have you talked to your fuel supplier? They usually carry additives

I actually just got a call back from the supplier. They have additives in it already that last 13-15 months and he said to add any other stabilizer after those have worn off. Otherwise if you add to soon like I did last time they can fight each other and reduce the overall life.

I also asked him about winter vs summer blend and he said winter is for sure longer lasting than summer due to the added volatiles mixed in to aid in cold weather starting.

So I basically got 4 years out of the worst case scenario last time, haha. Good to know all of these things and I hope it helps others that may stumble onto this thread.

EDIT, he also suggested no blanket otherwise it could corrode the tank over time with rainwater soaking it, instead add a tin roof over it if I am really concerned with the sun heating it up.

 

[Erik the Awful]

+1 on the tin roof.

Yeah, I was pretty sure you had a horizontal cylinder, that's why I even mentioned a bladder. A fuel cell style bladder probably isn't viable. They need inspecting and possibly replacing every few years, and they aren't meant to be deflated.

Is it possible to mount it vertically and put a floating mat on top?

I'm just thinking from my wine-making experience. I use a carboy for secondary fermentation because the narrowed neck limits the exposure to oxygen. That won't work with a container that's going to be less than full most of the time.

 

[Supercharged111]

How much cheaper was it for bulk delivery per gallon vs just getting it at the gas station right now?

 

[RichLo]

How much cheaper was it for bulk delivery per gallon vs just getting it at the gas station right now?

I get tax-free exemption for property maintenance equipment. Thats like 30-35c/gal off. Then its 87 octane NON-Ethanol with the added stabilizers that I didnt know about until yesterday. Which is more expensive and better gas. After all said and done its about 5c-10c/gal cheaper than 87 octane 10% ethanol pump gas.

I could get pump gas quality delivered for that tax-free discount but I want non-ethanol.

Plus I like having bulk gas and propane on my property for emergencies. I like knowing that if needed I can run my generator for any reasonable amount of time to keep my house warm and fridge/freezer cold.

I also have two large propane tanks for home heat that I fill once a year in the summer when its cheapest. I save money and know that I wont run out if there's another propane shortage like 2012... I was paying upwards of $5/gal for propane that winter which the summer before was selling for $0.69/gal. That winter made me buy the large tanks.