Gasoline stabilization additives for hybrid EVs that just wiff gasoline

I am a new (less than one month) 2018 Chrysler Pacifica Plug-In Hybrid. Going great, no problems, I’m just climbing the learning curve in this new world of electric or electric-gas hybrid vehicles.

The Chrysler Pacifica Plug-In Hybrid is billed as getting 30ish miles per full charge before kicking into gas/hybrid mode, and that is consistent with my experience, typically something in the low 30’s. No complaints - it’s working great!

It turns out, though, that my driving patterns are such that in the first 500 miles driven, only about 5-6 miles have been on gasoline - that is, most of my daily driving is short distances so that most days I do not fully discharge the battery. If this keeps up, with only a few percent of my miles drawing on gasoline on average, one tank of gasoline theoretically could end up lasting a year or longer. Of course, one exceptional road trip would change that quickly, so it’s likely that once or twice a year the tank would get flushed with fresh gas, but it still means that for months at a time I may be pushing “old gas” through my system before a “fresh” fill up.

Hence my question:

Should I use a stabilization additive with my gasoline? Joe Homeowner is supposed to use such things in small engines like lawnmowers and chain saws to prevent varnishing and other gunk buildup through off seasons that can cause engine performance to degrade, so does the same thinking apply to gasoline that may sit around in my Hybrid EV gas tank for months at a time? If so, what additive should be used? In this brave new world, does there even exist yet a trustworthy additive to deal with this issue?

By the way, my Pacific is recharged using solar energy - awesome. :slight_smile:

It won’t hurt to add some, I’d use Stabil. But check your manual, it may not be needed. I think the Chevy Volt has logic that runs the gas engine enough to avoid stale gas issues - yours might, too.


Agree with @texases, it couldn’t hurt to add some StaBil every time you fill up. Modern 10% ethanol gas really doesn’t store very well beyond 3 months or so. But look to your owners manual to see what Chrysler recommends.

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The longer the gas is going to sit in the tank is the more you need stabilizer.
That does NOT mean you need more stabilizer, it means you need stabilizer more.
Use the proportion recommended on the stabilizer bottle.

It seems that this question should be asked at the dealer who will be handling warranty claims .


I sent my Chrysler contact your question. I will let the thread know if I get any meaningful info. I think this is an excellent question and may be worth a focus story (including Prius Prime and other similar vehicles). Some vehicles of this type, do have a plan for this including running the gasoline engine periodically, even if it is not needed, to ensure fresh fuel.


Did you ever see one of those old gasoline pumps with glass globe on top? The gas came up from the storage tank then through the globe to advertise its cleanliness. We don’t have those anymore because gasoline is clean.

Do you remember all those ads for gasoline with additives (platformate!) and detergents? I remember one which looked like a front-load washing machine, the gasoline sloshing around to signify that it had detergent in it. You don’t see those anymore because all gasoline has detergents now.

I’ve gone 18 months without buying gasoline and had no problems. I put in a bottle of additive annually, the $1 stuff that claims to clean gas lines or carbs or injectors (I don’t care.)

I think these ‘bad gas’ stories are either exaggerations or mistakes. Maybe if you have a jet engine or a turbine…

Nobody’s talking about “bad gas”. The best gasoline is still a blend many natural hydrocarbons that can naturally fractionate to some degree over time (esp. exposed to cycling temperatures) and can coat (“varnish”) exposed parts over long periods of time. No fault of the gas, no fault of the auto maker, no fault of the operator. Just happens. Gasoline stabilizers exist to stall or slow such natural creep to limit potentially adverse effects.

The question is not whether such things happen (they do); the question is whether additives are warranted in the relatively new circumstances found in some of the new gas-wiffing hybrids (like mine). These vehicles include a lot of new features and controls, even new transmissions and engine cycles. It’s worth considering whether there may be new guidance on this point.

The best quality answer I have so far from offline sources is consistent with your remark about “18 months”. I’ve heard in general terms that varnishing is not a problem over a time of 1-2 years, but vehicles non-operational over periods of 2-3 years should be treated. That “should” mean that additives are not needed for the kind of driving I do, but I’m interested to hear other views.

OK, so I suspected Chrysler had thought of this, but I wanted to check. Indeed, Chrysler has programmed your new Pacifica Hybrid to manage the fuel for you, so that additives are not required to keep the fuel “fresh.” I reached out to an employee of Chrysler in communications. She verified with the technical staff that, “The vehicle monitors the age of the fuel in the system and will run the engine as needed to burn through older gasoline before it becomes an issue.” Other vehicles which combine electric drive with gasoline engines do this as well. I could not locate and article on the subject I liked, so I am going to write one :slight_smile: However, this link (from Chevy) will help explain the general idea.


Thanks for the great reply! That Chevy link is very helpful. Though mine is a Chrysler, that’s a very helpful orientation to what is very likely the case in mine as well.

I suppose I have not run my Pacifica long enough yet to experience any of the automated messaging or maintenance cycles mentioned, but I will better understand what’s going on when they (probably) come around.


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Happy I could help. I really love that Pacifica Hybrid. If you have any good news at tax time confirming you were able to use the full federal deduction that might make a great upbeat post.

I’m counting on it! All this great fuel economy does not come cheap! :slight_smile:

Ok, more information. Interesting, too.

I finally got a call back from the service manager at the Chrysler dealer from which I bought my Pacifica Hybrid. Armed with the information from @Columnshifter (including the linked Chevy article) we had a nicely-informed discussion of the matter.

First, the remarks of @Columnshifter and the general discussion in the linked Chevy article are all on point. My notes following add more, but relate to the Chrysler, not the Chevy (though much of it probably applies to the Chevy, too).

Interestingly, as relevant background, my service manager told me that here in San Diego, they have a lot of experience with Navy/Marine service people being sent out on 6 month deployments and coming home to cars that won’t start or run properly because of gas-related problems. Consequently, they recommend to all military to add gas stabilizer before such long deployments. With this as background, he noted that dwell times of several months are pushing into this regime where they begin to see problems, so he would “definitely” recommend using a gas stabilizer in my case.

I asked further about the “smart” functionality built in to somehow monitor gas aging and “burn it off” automatically before aging effects creep in. He confirmed that the Pacifica utilizes such functionality, but recommended the stabilizer anyway, noting the following: Using stabilizer preserves or extends the “fresh” condition of the gas, so that by using stabilizer one is not only avoiding adverse effects of gas aging, but also avoids the automated burn-off of the gasoline since the system sensors can tell that the gas is still “fresh”.

That is … without stabilizer the car will automatically burn through gas at a pace that avoids aging problems, but with stabilizer, the automated burns should not kick in. So here’s an economic and ecological reason to use stabilizer - save the money, fossil fuel, and carbon load of a couple of tanks of gas that don’t get burnt up in automated maintenance cycles.

All of that surprised me quite a bit. I asked for references for following up (user manual section, links), but his sourcing was Chrysler internal stuff.

By the way, after that discussion I halfway expected him to point me to Chrysler’s own gold-plated specially-trademarked hybrid gas stabilizer, manufactured to pass muster under warranty, but no - he just recommended STA-BIL from the Home Depot, assuring me that it would not invalidate my warranty.


Good info, but I’m smelling some BS. I can’t imagine how the car would know you added stabilizer.

But I don’t argue with his advice, StaBil is cheap, get the big bottle at WalMart, you’ll be set for a LONG time!

I hear you, and I want to know more about how they automate the monitoring of that.

But my service manager was quick to say that the car does not infer gas age by tracking how much gas is added when, but by a direct sensing of the gas in the tank. I would like to know how, but I don’t. My guess would be that it would involve a sensor that samples the vapor in the tank as that is well-developed road-tested tech (think oxygen sensor). The mix of volatile components that make up the vapor change as the gas ages. But they probably monitor more than just the vapor and I’d like to know what and how.

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You may already know this, but page 168 of the owners manual has a few paragraphs on this. It does not give the exact methods by which it works, but it does say some good stuff. [Check it out here](file:///C:/Users/Owner/Downloads/2018-Pacifica_Hybrid-OM-3rd%20(4).pdf).

The manual reads like it’s according to time, including “Fuel Freshness is recalculated whenever fuel is
added to the vehicle’s fuel tank”.

you plug in every night? how about not plugging in for a day or 2 or 3 and forcing the gas engine to run and burn up your old gas? you can do this once a month. the battery will be depleted and it will go into gas mode if you want to move. what if you go off the grid? like camping in the boonies for a week? no electricity

The car monitors the age of the gas, and runs when it needs to.
“If the vehicle
enters Fuel and Oil Refresh Mode, due to fuel which has
been in the fuel tank for a long period of time (becoming
stale fuel), the engine will run whenever the vehicle is
operational (no electric only operation) until the low fuel
level warning is activated. It is possible to exit the Fuel and
Oil Refresh Mode sooner by adding new fuel to the
vehicle’s fuel tank.”

No need to force it.

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The best gasoline would be pure ‘octane’ and heptane. I know that nobody makes that: it would cost too much. But it wouldn’t have the problems you mention.

Detergents clean up the varnish. I re-built my carburetor for the first time after 30 years and found no sign of varnish. I think varnish is a relic of the before-detergent past.