Keeping gas fresh

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graememwl

Well-known member
Joined
Jan 10, 2018
Messages
67
Location
San Francisco Bay Area
The only time I have used the Rex is when I deliberately ran the batteries down below 6%. Does anyone run something like sta-bil fuel stabilizer to keep their gas "fresh"? I'm thinking I'll just code my '15 Rex to allow Maintain SoC and run the gas out every quarter to minimize "gunk" buildup in the system.
Opinions?
 
Personally, I think it's a decent idea. But, one thing BMW did was to pressurize the tank. That helps to minimize any of the more volatile components in the gasoline from evaporating, which probably makes a difference4. So, it probably wouldn't matter, but still, to be cautious, can't hurt. An extended run would also help to redistribute the oil and clean out any condensation in parts that should help in the long term.
 
With the pressurized tank, if you put in high octane it should last at least a year. At least that's what I've read.
 
I use fuel stabilizer in my snowmobile, snowblowers, generators, lawnmowers, outboards and i3 during the off season or if fuel won't get used for an extended period of time. In my experience fuel stabilizer helps. Less varnish in float bowls (carburetors) and less plugging of injectors (fuel injection). I am of the opinion that the i3 maintenance cycle is designed to reduce injector clogging. To read more about this issue please see https://www.injectorrx.com/clogged-fuel-injectors/
 
I would suggest running the REx every few months or so to keep the internals lubricated, as Jim pointed out and for the reasons TOEd pointed out. I think you may be asking for problems if you don't allow it to run ever so often. I always put premium fuel in mine since it's more stable but someone living in higher elevation (Colorado?) had some back firing issues when using premium fuel.
 
brorob said:
I would suggest running the REx every few months or so to keep the internals lubricated, as Jim pointed out and for the reasons TOEd pointed out. I think you may be asking for problems if you don't allow it to run ever so often. I always put premium fuel in mine since it's more stable but someone living in higher elevation (Colorado?) had some back firing issues when using premium fuel.
BMW programmed the REx to come on every so often to do what you just described. It's automatic, you don't have to do anything. At least that's how mine works.
 
theothertom said:
BMW programmed the REx to come on every so often to do what you just described. It's automatic, you don't have to do anything. At least that's how mine works.
That's true but if the gas tank is less than 1/4 full then the maintenance cycle won't start, unless they have changed this with a recent software update. I've seen some owners state that they keep their tanks low since they don't use the REx, which is why I added my 2 cents about running it occasionally.
 
With my 2015 REX, I went 2 years without using the REX or adding gas. The maintenance cycle got the gas level to 1/2. On the next cycle, I had a bad smell and a check engine light. I took it in and the dealer said "no problem found but was I using premium gas?" I filled the tank and started using the REX.

The way I drive, I would use the REX for a few miles and arrive home. I'd get the "don't leave the car with a low charge warning" so I'd charge it. At that rate, it would take another two years to get down to say 1/4 level. I coded the "hold Soc" and was able to get the level down to 1/4 in under a year.

I obviously don't need the REX but this is my first EV. Next time....
 
I think one reason why BMW pressurizes the gas tank is to help prevent the more volatile components of the fuel from evaporating. Yes, there's a vapor recovery system, but with long-term EV use, and no fuel use, that would get saturated. Anyway, if you're worried about it, you might try some fuel stabilizer. If you're really worried about it, you might find a place where you can buy MOGAS (unleaded, aviation fuel), but it will cost you. That has a bunch of stabilizers in it already and is alcohol free. Where I live, I can't find any car gas that doesn't have ethanol in it.
 
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