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Discussion Starter · #1 ·
We have been driving around with a virtually full tank of fuel for a month or two wondering why we didn't just half fill the tank? I think that is what we will do while we are using EV mode for most of our journeys. What is the point in carrying the equivalent of young teenager around with us?
 

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For city driving there is no need for fill the tank till maximum. I usually keep mine between 20-50%.
But for long trips it is easier to have more range ofcourse.
 

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2019 Ioniq PHEV Preferred
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We have been driving around with a virtually full tank of fuel for a month or two wondering why we didn't just half fill the tank? I think that is what we will do while we are using EV mode for most of our journeys. What is the point in carrying the equivalent of young teenager around with us?
One reason I know of is that having a full tank can prevent condensation inside the tank, and therefore corrosion. Is that sufficient reason? Probably not. I've never heard of that being problem for anyone but I suppose it depends on weather over many years.
 

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You should fill you tank up enough so that you use it up over 3-4 months (or sooner). Gas that sits in your tank for an extended time will go stale as it outgasses. This won't hurt the engine, most likely, but it will mean it won't be able to generate as much energy from burning that gas, so you're just wasting money.
 

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We have been driving around with a virtually full tank of fuel for a month or two wondering why we didn't just half fill the tank? I think that is what we will do while we are using EV mode for most of our journeys. What is the point in carrying the equivalent of young teenager around with us?
As another member said, fuel gasses can escape. I'm pretty sure regulations only allow for very little. (It's pretty much a sealed system) As for corrosion, I'm just assuming it is a plastic tank with plastic internals other than the pump and wiring itself. I think you would be safe at 30-50 percent full. As long as you use it before the fuel becomes bad.

Maybe use non-ethanol fuel if you know it will be in the tank for long periods of time.
 

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As another member said, fuel gasses can escape. I'm pretty sure regulations only allow for very little. (It's pretty much a sealed system) As for corrosion, I'm just assuming it is a plastic tank with plastic internals other than the pump and wiring itself. I think you would be safe at 30-50 percent full. As long as you use it before the fuel becomes bad.

Maybe use non-ethanol fuel if you know it will be in the tank for long periods of time.
There are also fuel stabilizers you can add to make it last longer, though honestly I'd just add only enough that you'll use it in a reasonable time.
 

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Discussion Starter · #7 ·
My post was really about saving weight and the subsequent increase in range.
 

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Just had my first fill up after using the full tank the car came with. Going with half tanks from now on, unless I'm going on a road trip and need the 1000km of range.
 

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One reason I know of is that having a full tank can prevent condensation inside the tank, and therefore corrosion. Is that sufficient reason? Probably not. I've never heard of that being problem for anyone but I suppose it depends on weather over many years.
I think most tanks are plastic these days.
What do you think of maintaining just 1/4 tank in the summer months.
I've heard that the I.C.E. will start up on it's own when upper cylinder lubrication gets too dry. I wonder if anyone has experienced that?
I try to use the I.C.E. once a month for this reason during summer.
 

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I think most tanks are plastic these days.
What do you think of maintaining just 1/4 tank in the summer months.
I've heard that the I.C.E. will start up on it's own when upper cylinder lubrication gets too dry. I wonder if anyone has experienced that?
I try to use the I.C.E. once a month for this reason during summer.
The full tank recommendation to prevent corrosion was for a 2007 German car I had. You may be right that recent Hyundai’s have plastic. I would have to look it up.

I’ve had my Ioniq ICE start up on its own a few times, and you might have answered why. I could only suspect it was some kind of prevention or precaution.
 

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Just doing the math(s) on this with regards to the OP's question. According to the specs, the current Ioniq PHEV has the following fuel tank size:

43 L = 11.4 gallons (US) = 9.5 gallons (UK)

Doing the math(s) in US figures, a fully filled fuel tank would weigh 11.4 gallons x 6.3 lbs / gallon = 72 lbs = 32.6 kg

So, a half filled fuel tank would weigh 36 lbs = 16.3 kg, saving you from carrying around that equivalent amount. So, running with a half a tank would save a bit of weight, though not a great deal. Not quite the weight of a small teenager as suggested. I'm not well enough equipped mentally to do the math(s) on the range increase from that small decrease in weight, but maybe one of the gurus on the forum could weigh in. But, I imagine it would be pretty small. If anything, I myself could stand to lose that much weight, so maybe me doing that and running with half a tank might make a difference in my daily travels.
 

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Well, 36 lbs is 1% the curb weight (3417 kg) of the 2019 PHEV Limited. If you assume a 1% weight reduction increases the range by 1% (which isn't an accurate approximation, but an easy one) the range increases from 29 miles to 29.3 miles. About 1600 feet.

In any case, I think it's safe to say reducing the amount of fuel you carry will never increase range by more than 1 mile, probably not even 0.5 mile.
 

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I looked it up and the US EPA says the following:

"An extra 100 pounds (45.3 kg) in your vehicle could reduce your MPG by about 1%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones."

So, if we go by this as a rough rule of thumb and use the numbers I posted previously, the effect on range at a half a tank vs full tank will likely be somewhere in the 0.36% area (36 lbs / 100 lbs per 1%). Using the US EV range of 29 miles (46.7 km) * 1.0036 = 29.1 miles (46.86 km). So, per full ev battery charge, you'll be netting roughly an extra 1/10 of a mile (1/6 of a km) by running a half tank vs a full tank. For another perspective, driving 1,000 ev miles with a half a tank will net you an extra ~3.6 miles over having a full tank. For our metric friends, you can substitute miles for km directly, so driving 1,000 ev km with a half a tank will net you an extra ~3.6 km over having a full tank.

As the old saying goes, "The juice might not be worth the squeeze" in this case.
 

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I looked it up and the US EPA says the following:

"An extra 100 pounds (45.3 kg) in your vehicle could reduce your MPG by about 1%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones."

So, if we go by this as a rough rule of thumb and use the numbers I posted previously, the effect on range at a half a tank vs full tank will likely be somewhere in the 0.36% area (36 lbs / 100 lbs per 1%). Using the US EV range of 29 miles (46.7 km) * 1.0036 = 29.1 miles (46.86 km). So, per full ev battery charge, you'll be netting roughly an extra 1/10 of a mile (1/6 of a km) by running a half tank vs a full tank. For another perspective, driving 1,000 ev miles with a half a tank will net you an extra ~3.6 miles over having a full tank. For our metric friends, you can substitute miles for km directly, so driving 1,000 ev km with a half a tank will net you an extra ~3.6 km over having a full tank.

As the old saying goes, "The juice might not be worth the squeeze" in this case.
What a great double entendre! You guys are a sharp group! Makes me even more proud to be driving my PHEV around. Like you guys, my 2019 is awesome!
 

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I’ve had the car for a month now and my tank is at 3/4. I didn’t really need to use that 1/4, I just realized if I didn’t it might degrade or something.

Since I can actually run on BEV mode most of the time I might also just keep 1/2 or even 1/4 of the tank full in the future. Not just to reduce weight but to leave room for fresh new fuel when I go on a road trip.
 
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