DenverJohn

A very general concern and here seems as good a place as any to ask. I am not driving my Merc near as often of late and I am concerned about gasoline aging just sitting in the tank. I'll sometimes go several weeks without using even a quarter tank, ( E-350 so like an 18 gallon tank?) when I typically fill up. I have always been in the habit of keeping a full tank, especially during winter's cold wet weather. (The concern always being getting water in the fuel from condensation.) Since gasoline additives like Sta-bil are not advised or approved by Mercedes here's my question. Am I better off filling the tank down just a quarter tank or wait until I am closer to only a quarter tank or less and get a full tank of fresh gas? The last time I was even below a half tank and filled up was Late October. Any thoughts would be helpful. If it matters I am in an area with cold wet winters in the northeast US and the car is always garaged where the temp rarely falls below 40F even when outdoor temps can drop to the teens. Thanks in advance.

john

rapidoxidation

Stay away from ethanol contaminated gasoline (alcohol attracts moisture), keep a full tank, and don't sweat it.

KEY08

You could go a year or longer with no issue. Stop worrying. Have you ever driven by a new car lot and have seen the same new cars sitting there in the cold winter for months at a time? Never moving?

DFWdude

I refill my tank once every three months, whether it needs it or not. Often with 3/8 of a tank left. No worries.

Not sure how to avoid "ethanol contaminated" gasoline. That's all we have here in Texas.

Left Coast Geek

E10 is 90% gasoline, which is hydrophobic, and 10% ethanol which is hydroscopic. the phobic wins.

the bigger issue with storing gas for any length of time is that the lighter components and additives of the gas itself evaporate over time and leaving the waxier components behind to gum things up.



(edited, I said water instead of ethanol, silly me)

DenverJohn

I am not sure I would want to take my queue (regarding technical issues) as the best practice for taking care of my car from what is done on the sales lot.

rapidoxidation

I'll overlook you saying E10 is 10% water, but I have to say the hydrophobic doesn't always win. As such, boat docks tend to sell ethanol free fuel.

KEY08

Ok, fine. I have a car sitting in my garage since November and it won't see the light of day until April. Full tank of gas just sitting there on a battery tender. I have been doing this with specialty cars for 45 years. They don't choke out and die in the spring when started or run rough and blow up. I suggest you simply schedule longer trips and use more gas if you think it will help.

DenverJohn

That is my concern more so than any issue with water or moisture, considering the fuel tank is relatively sealed. So which is best? To keep topping off the tank or let it go lower and get a more complete tank of fresh Gasoline?

DenverJohn

I was hoping there might be some thoughtful, more technical answers here considering the sight but ... I see I was wrong. thanks anyway.

KEY08

Personally, I think the gas will stay fresh for a long time so you should work to keep the tank topped up on really cold weather spells. My idea of topped up is anything over 3/4 tank of gas. If you aren't driving that much it shouldn't be too difficult to maintain 3/4 and above when it is very cold out. As the weather warms above freezing it is not as important to continue topping it off. Once again, the gas will not go bad on you in just a few months. That was my main point all along.

rapidoxidation

I had a client who left their junky old ford explorer outside with the tank full and battery disconnected. For two years. I connected the battery and it started with only a few seconds if cranking.

Don't worry. Drive happy.

no_mulligan

Is it that you don't drive much at all or just not this MB? Transfer the “old“ fuel into an actively driven vehicle and put in 5 gallons of fresh to get it to the gas station.

DFWdude

That sounds like work. Siphoning in this cold weather is not fun, either.

IMO, maintaining battery charge is 10-times more challenging than worrying about gas in the tank.

Arrie

In winter time alcohol is VERY GOOD to have in the gas tank. Alcohol does attract water ( or water attracts alcohol) because water dilutes alcohol and it still burns in the engine but that is not why you want alcohol in the tank. It is to keep that damn water from freezing in your fuel system.

In some European countries in the north the fuel does not have alcohol in it that you pump in your car, or at least did not use to have. To be able to run in very cold winter weather you just had to buy a bottle of alcohol that you added as you filled up. Usually 1 liter bottle for about 40 liters of fuel. And this alcohol was about 90% strong. Without it the fuel lines froze as there ALWAYS is water in the fuel you pump in your car,

Alcohol attracting water is good in your fuel tank as it prevents water from causing issues during winter months. Always fill up only with ethanol containing fuel during winter months where temperature drops below freezing-

And this same method is used with windshield washer fluid too. You can buy summer grade but for winter it is made to withstand down to -30F or something like that and it is done by adding alcohol in that same bottle of soapy water that the summer grade is.

davidjohnbamber

You could always buy some ethanol free racing fuel.

bmwpowere36m3

Personally I think your overthinking it... several weeks is nothing.

I rarely drive my M3, hell I think it has 2 year old gas in it... dosed with Marine Stabil. Though, I wouldn't advocate keep gas that long, but I've been caught up in many projects and the car has been somewhat neglected over the past few years. Still runs and drives great.

Anything less than 6 months or so I wouldn't worry about... if you are add stabilizer. My general "storage" mantra is fill up with stabilized gas and run vehicle/equipment to circulate stabilized gas. The only thing that gets "special" gas is my 2-stroke equipment which I fill up with canned ethanol premix. Otherwise all gas in CT is at least 10% ethanol.

ygmn

USE STA-BIL - No issues then.

Manufacturer = STABIL Car, Boat & Small Engine Fuel Treatments | Gold Eagle

Been around for years - we have always used it in boats and lawn equipment really anything that sits for more then 3 months.
We like the one that is designed for ethanol fuel to help fight water.

Buy some stick it intank... add it to your lawnmower, sno blower and small engine tank. keeps the carbs nice and fresh for the summer.

LILBENZ230

My car was just in the shop for 6 weeks, no battery tender, no driving, car is fine. E350 has 21.1 gallon tank.

nota_amg

Buc-ee's sells Ethanol Free Fuel, Don't know if they've made it to Dallas yet though... I've seen E-Free at a few Sunoco stations as well.

DFWdude

Thanks. There's a Buc-ee's 14 miles from my home on an interstate i seldom use. I will check next time I'm there to see how they label the pump.

I get a dollar per gallon off at the station I habitually use. And they don't have Ethanol Free. So I haven't bothered to look around.