Extended RV Fuel Storage (Gas)

[ButchW]

I asked a question about old fuel and smog checks... Older Gas And Smog Test I've had about 1/4 tank of fuel in my MH for about 4 months.. I regularly start and run it for awhile (monthly or so).. I go thru periods thru out the year where I don't use the RV.. At the most 6 months, but most times no more than 2-4 months... My question here is what is the best way to store gas in the MH... Full, and not worry about the fuel getting old, or try to use up most of the fuel, and when near empty, fill with fresh fuel (diluting the old fuel)... I guess what I'm asking is, am I better off storing, with a full tank of older gas, or letting it run down, store (with just a little old fuel), then put fresh fuel in when I'm ready to use it?...
Butch

 

[Fyrflie]

I have read on multiple sites that you should store your MH with a full tank. Less chance of condensation forming in the tank eventually creating other issues.

 

[Mark_K5LXP]

I think fuel level mattered more in the days of yore before evaporative emission systems were implemented. The prevailing theory is the less air in the tank the less it would "breath" and ingest moisture. With contemporary closed systems I'm not sure there's that much air exchange happening. The timeframes you mentioned I don't think merit much intervention in any case, I would just leave it at whatever level and refill as needed. Something to look for is non-ethanol gas, I think that keeps a bit better or dump in some fuel stabilizer if it makes you feel better about it.

Mark B.
Albuquerque, NM

 

[Western Slope]

In a dry climate like in Southern California and where we live in Western Colorado I'm not concerned about moisture in the tanks. Both our 1978 Chevrolet LUV and 1978 Mercruiser 5.0L gas engines get stored for very long stretches with gas up to 10 years old and still run fine. Both were purchased and used in Southern California, then in Colorado. I use Sta-Bil.

 

[Boat Bum]

It's my understanding and practice with my 120 gal fuel tank on my boat for 23 years that prior to ethanol conventional wisdom suggested storing the fuel tank full; keep in mind this will sit for six months in Northeast winters.

With the addition of 10% ethanol in our gas around here it then became the opposite, the logic being that due to the phase separation over time it was better to store with a 1/4 tank or less. I did it both ways and always added Startron, never a problem.

I also know of gas years old that fired right up so go figure...

 

[Tulecreeper]

It's my understanding and practice with my 120 gal fuel tank on my boat for 23 years that prior to ethanol conventional wisdom suggested storing the fuel tank full; keep in mind this will sit for six months in Northeast winters.

With the addition of 10% ethanol in our gas around here it then became the opposite, the logic being that due to the phase separation over time it was better to store with a 1/4 tank or less. I did it both ways and always added Startron, never a problem.

I also know of gas years old that fired right up so go figure...

I use Sta-Bil, but same outcome.

 

[Arch Hoagland]

I always fill up prior to storing mine beside my house.

If need be I can run my generator for many days if the power goes out and run an extension cord into my house for the refrigerator and freezer plus lights.

If a natural disaster hits I can get out of Dodge quickly.

The Loma Prieta Earthquake in 1989 shut down all gas stations in our area for four days. I keep my vehicles topped off because of that event.

When I leave on a trip I like to pull out early and not have to go to a gas station.

 

[Boat Bum]

I use Sta-Bil, but same outcome.

I've used Sta-bil but found the Startron to be a better value.

 

[ButchW]

Does Sta-bil or the like affect smog test?
Butch

 

[Boat Bum]

I've only ever used it in seasonal gas engines which don't require smog testing.

 

[Ray-IN]

Just for conversation; I just bought a new 4000W Pulsar dual-fuel portable genset. The instructions say, before storage run the tank and carburetor dry of gas.
Having said that; I have an old gasoline powered farm tractor that has sat for up to a year without being started. I do shut of the fuel tank and run the carburetor dry. Every time it starts and runs reliably. The only thing I do is add 2oz of SeaFoam to each of my 5G cans before re-filling them.

 

[Fyrflie]

Arch brings up some good points about being prepared for natural disasters. It is truly something we should all be thinking about.

 

[Skookum]

In small equipment, I don't heed the directions to shut off the fuel and run the carb dry. In my experience, the carburetor never fully empties and small amounts of fuel sit in there and it eventually gums things up. Any rubber not exposed to fuel dries up.

I do keep the tanks full, and I use 91 octane (highest we can get here), ethanol free, to avoid the phase separation. I also regularly run my equipment, change the oil, and if I haven't used the gas in a year, I empty it, fill it with fresh, and run it through. Since doing this, I've never had a small engine carburetor foul up. Ever. I mix my small equipment gas with ethanol right in the can so any gas on the shelf is also maintained from the start.

Large vehicles I treat with the same concept. Keep the tanks full when storing, use high quality fuel. Run them to operating temperature, including the transmission, when possible. If it's been a year I try to empty the tank through normal use.

Straight from the US EPA:
TL;dr: Stabilizer doesn't have a negative effect on emissions, and it's virtually worthless in improving emissions and fuel economy, but it does prevent fuel from degrading over time.

07/13/2000: EPA Tests Find that Fuel Stabilizer, Alleged Emissions Control Device, Does Nothing

 

[ButchW]

In small equipment, I don't heed the directions to shut off the fuel and run the carb dry. In my experience, the carburetor never fully empties and small amounts of fuel sit in there and it eventually gums things up. Any rubber not exposed to fuel dries up.

I do keep the tanks full, and I use 91 octane (highest we can get here), ethanol free, to avoid the phase separation. I also regularly run my equipment, change the oil, and if I haven't used the gas in a year, I empty it, fill it with fresh, and run it through. Since doing this, I've never had a small engine carburetor foul up. Ever. I mix my small equipment gas with ethanol right in the can so any gas on the shelf is also maintained from the start.

Large vehicles I treat with the same concept. Keep the tanks full when storing, use high quality fuel. Run them to operating temperature, including the transmission, when possible. If it's been a year I try to empty the tank through normal use.

Straight from the US EPA:
TL;dr: Stabilizer doesn't have a negative effect on emissions, and it's virtually worthless in improving emissions and fuel economy, but it does prevent fuel from degrading over time.

07/13/2000: EPA Tests Find that Fuel Stabilizer, Alleged Emissions Control Device, Does Nothing

That is a device… Not a fuel additive… The rest of what you posted makes since to me… Thanks…
Butch

 

[DonTom]

I use Sta-Bil, but same outcome.

Right on the bottle of Sta-Bil it says "will keep gasoline fresh for up to a year." Since I have no problems with gas stored more than a year, I have to wonder if the gasoline will last longer than the Sta-Bil.

Where extra cold is when fuel phase separation can become a problem.

-Don- (in snowy Reno, NV)

 

[Tulecreeper]

Right on the bottle of Sta-Bil it says "will keep gasoline fresh for up to a year." Since I have no problems with gas stored more than a year, I have to wonder if the gasoline will last longer than the Sta-Bil.

Where extra cold is when fuel phase separation can become a problem.

-Don- (in snowy Reno, NV)

I use it because I have a problem with gas that has been stored for more than 6 months. Even using the Sta-Bil, I seldom have gas last more than a few months, but I like the wiggle room.

 

[DonTom]

I do keep the tanks full, and I use 91 octane (highest we can get here), ethanol free

Here in Reno, I have only seen the ethanol free stuff in 86 octane. I have never seen it at all in CA. Perhaps not even sold in CA.

But AFAIK, the octane has nothing to do with fuel phase separation. AFAIK, octane is only used to raise the temperature where the explosion will happen inside the combustion chamber. In some engines, with too much octane it will not run correctly as it will not get hot enough to make full explosions. If octane is too low, it explodes before is should (pinging).

IMO, it's best to always use the octane your owner's manual says it should use. But too many manuals only give a minimum number and no max. There is also a maximum octane an engine can use.

-Don- Reno, NV

 

[DonTom]

I use it because I have a problem with gas that has been stored for more than 6 months. Even using the Sta-Bil, I seldom have gas last more than a few months, but I like the wiggle room.

I often have gas stored for close to a year in many engines (mostly motorcycles). No problems yet, but they are normally started on warmer days which helps.

-Don- Reno, NV

 

[Skookum]

@DonTom that is correct, follow the recommendation for octane rating in the owner's manual.

Many Stihl products with small 2-stroke engines stipulate 89 octane minimum, which is why I use higher. I use 91 ethanol free for the absence of ethanol, specifically. The extra octane is not required by my Honda Lawn mower, however, 91 does not hurt it (it just wastes money), but the absence of ethanol can be beneficial when storing for longer periods of time. Using 91, I also don't have to keep separate cans of fuel with different octanes. Yard machines get 91 octane ethanol free at my house. Some make use of the higher octane, and others don't.

I'm not surprised California does not sell ethanol-free gas, but I don't live there

Edit: I also live near sea-level. I'm sure someone from Colorado will be along shortly to tell the world how their minimum-87 octane cars and machines utilize 85 octane just fine. It's an elevation thing.

 

[DonTom]

I'm sure someone from Colorado will be along shortly to tell the world how their minimum-87 octane cars and machines utilize 85 octane just fine. It's an elevation thing.

Not so much in modern EFI engines. But that doesn't apply to lawn mowers and Onan Gennys. IMO, both use an ancient design, especially the gennys. Even my Honda lawn mower needs no elevation adjustment. It has a CV carb.

My 2022 RV's Onan has an elevation adjustment. No CV carb. 1960's design, IMAO.

-Don- Reno, NV