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Exaggerated. Last week I reached a speed of 130 km/h without knowing it ( chatting with 3 other passengers) Specific fuel consumption may have increased somewhat but not in the amount as shown by the graph. How did you get this graph? My trip computer did not crash as this graph suggests. On the other hand it is a known fact that maintained speeds above 120 km/h does not favor your wallet.
 

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Car and Driver has a new review (a few days ago) of the Kia Niro and said the fuel efficient version got 42 US mpg at a steady 75 mph over a 200 mile loop. Your comparable figure is 43 US mpg (per Fuelly). As the Niro has much higher drag than your Ioniq, your mpg is indeed low. It could be you have the 17" wheels, or even more likely that you had adverse wind conditions.

Car and Driver has not yet done a similar test of the Ioniq. I'd love to know what the comparable mpg figure is. It is difficult to find reviews with the same testing methodology, and I think high speed testing is the way to go. Consumers Reports will eventually have some comparable mpg figures on both cars, but I feel certain they don't go that fast.
 

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Discussion Starter · #6 ·
Exaggerated. Last week I reached a speed of 130 km/h without knowing it ( chatting with 3 other passengers) Specific fuel consumption may have increased somewhat but not in the amount as shown by the graph. How did you get this graph? My trip computer did not crash as this graph suggests. On the other hand it is a known fact that maintained speeds above 120 km/h does not favor your wallet.
It is the graph is links points that are the distance between fuel-ups divided by the volume of petrol bought at fuel-up. It is not a estimate over a few kilometers, but an actual measure over hundreds of kilometers.

The data is accurate but the scale of the graph is misleading because the orgin is not zero as it should be.

In terms of fuel consumption as opposed to fuel economy, it means that when driving hundreds of kilometers below 110km/h I get a fuel consumption of 4.7l/100km, whereas when driving hundreds of kilometers above 120km/h (not just temporarily without knowing it, but deliberately for many hours) I get a fuel consumption of 5.7l/100km.
 

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Exactly, but I don't consider this increase as dramatically.
The graphs suggest a dramatic fall in efficiency. Do not expect your mpg gets better when hitting the throttle.
 
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Discussion Starter · #8 ·
Car and Driver has a new review (a few days ago) of the Kia Niro and said the fuel efficient version got 42 US mpg at a steady 75 mph over a 200 mile loop. Your comparable figure is 43 US mpg (per Fuelly). As the Niro has much higher drag than your Ioniq, your mpg is indeed low. It could be you have the 17" wheels, or even more likely that you had adverse wind conditions.
Interesting read and comparison. I believe there are two things conter-balancing the aerodynamics factor.
1- The "executive" trim of the Ioniq in south-western Europe is very fully and therefore heavily equiped. The 17'' wheels and all other lighter equipements add up and end up impacting weight. Therefore it may be compared to the "Touring" trim of the Niro, rather than the
FE trim.
2- The autoroute speed is not 75 mph but 80 mph. According to Hyundai the Ioniq is designed to leverage EV mode up to 75 mph... There are 5 mph missing for French highways.

In France nowadays when the speed limit is set at 130 km/h, all cars drive at 130 km/h. Only trucks drive below that speed. It makes driving at lower speed unappealing, even dangerous. If one bypasses a truck at 120 km/h, cars coming behind will get annoyed and stick to one's tail.

I don't think adverse wind conditions were a substantial driver. It didn't seem very windy and it was a return trip, so wind slowing the car in one direction should have pushed it on the way back.
 

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The graph is very dramatic. This is due to the y axis starting at 50 mpg. If it started at zero that curve would be waaaaaay less noticeable.

The reality is you are talking about an 8 mpg difference. This appears to be an appropriate 14% reduction in mpg. The graph over states this pictorially.

There are lies, dammed lies, statistics and now graphs.
 

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Discussion Starter · #10 ·
I very much agree that those skewed graph scales are a problem, a sort of lie indeed. Most graphs found in the media and the Web use these skewed scales unfortunately.

However the graph happens to reflect the fact that the Ioniq fuel economy is very homogeneous until 75 mph or 120 km/h, and then drops quite suddenly.
 

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yep, that is where the EV motor cuts off under normal driving, as the wind resistance requires more power than the EV motor can provide on its own


above 75mph it drops down to a role of supplimenting the ICE power when accelerating / hill climbing rather than replacing it so far less of a positive effect on MPG
 

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I don't think adverse wind conditions were a substantial driver. It didn't seem very windy and it was a return trip, so wind slowing the car in one direction should have pushed it on the way back.
It can be difficult to tell how much wind there might be subjectively. When I notice a drop in mileage that I cannot attribute to any other reason like elevation gain, altitude, or temperature, usually a consult with a weather app will confirm that there was wind blowing in the wrong direction.

Wind shifts directions too! That is much more noticeable subjectively on a bicycle. Often there is a 10 mph headwind in the morning, then in the afternoon, a 10 mph headwind back. Super annoying. But even in a car, adding a 10 mph headwind will be similar to the difference between driving at 50 versus 60 mph with no wind. Significant.

I just found a much longer version of that Car and Driver Niro test here. Much more detail about how they do their high speed runs and comparisons with similar vehicles. There are a number of small discrepancies in the review, for example they noted a step in the rear cargo area area with the rear seats down, and had pictures to back it up. However, I didn't see any step on actual Niros at local dealers.
 

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However the graph happens to reflect the fact that the Ioniq fuel economy is very homogeneous until 75 mph or 120 km/h, and then drops quite suddenly.
Drag goes up by the square of the velocity. So the curve drawn on a linear scale should resemble a logarithmic curve. But it won't be a sharp step from 110 to 120, that is an artifact of both your graphing technique, and the anecdotal errors from a single(?) tank of gas.

Try this to confirm what I'm saying: Drive on a flat motorway one direction at 90 km/hr steady for a few km and take note of the average (average instant) mileage reported by the car. Then continue at 100 km/hr steady for few km and take note again. Repeat for 110, 120, and 130. Plot that on a graph and I believe it will look like a log function.
 

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Car and Driver has just published a review of the Ioniq. They seem to like it. Highlight for me was 45 mpg for Ioniq for all tested miles versus 42 and 44 mpg for two Prii reviewed recently. Highly anecdotal of course with multiple drivers and conditions and I hope they expand this review to an in-depth one where they do a high speed test of the mpg you can better compare to other cars. 42 mpg was the figure for the Niro at a GPS constant 75 mpg over a 200 mile loop. As the Ioniq is considerably more aerodynmic than the Niro, I'm expecting better mpg, perhaps 46 to 50 mpg (U.S.).
 

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Discussion Starter · #15 ·
Over the last few days I drove at 130 km/h with ACC instead of the speed limiter which is more of my habit. Apparently I had (downhill) EV stretches with ACC that didn't occur with the speed limiter at the same speed, and fuel economy improved a bit.
I can't be positive though, because the 130 km/h ACC experience was only 300 km long, therefore not a complete fuel-up.
 

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Guys, I don't know about all this.....

I've just finished doing my taxes this year and noticed that my available gasoline deduction had dropped considerably since owning my IONIQ (May 2017). Less than half from the previous year ..... And I have the Limited with the 17" wheels...... I also purchase the expensive no-ethanol gas too! So, this car is not doing me any favours tax-wise.

Ridiculously happily with this car.... It just works!!!
~
 

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In terms of fuel consumption as opposed to fuel economy, it means that when driving hundreds of kilometers below 110km/h I get a fuel consumption of 4.7l/100km, whereas when driving hundreds of kilometers above 120km/h (not just temporarily without knowing it, but deliberately for many hours) I get a fuel consumption of 5.7l/100km.
I had a life average of 6.18 l/100km with my Toyota Echo (Yaris in the rest of the world) over 329,000km, and was often in the 5.5 l/100km range on long open road drives at 110 to 120 km/h (which is pretty good seeing as how it was 2000 tech). City consumption could be as high as 6.5 or 6.7 l/100km. The reality is that with the inherent inefficiencies of a petrol motor, the harder it works, the more efficient it is. Sadly, electric motors are extremely efficient and do not "gain" efficiency with load. As soon as you get to that point where the a PHEV car switches to the ICE, either for speed or range, you're basically a regular car (with a heavy battery and electric motor as added weight) so you can expect your consumption to reflect close to regular ICE consumptions.

PHEV's are probably best suited to speeds less than 120km/h (<100 km/h would be better) and shorter range trips when they act as an EV with low drag and don't get the ICE inefficiency penalty.

OB
 

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As soon as you get to that point where the a PHEV car switches to the ICE, either for speed or range, you're basically a regular car (with a heavy battery and electric motor as added weight) so you can expect your consumption to reflect close to regular ICE consumptions.

PHEV's are probably best suited to speeds less than 120km/h (<100 km/h would be better) and shorter range trips when they act as an EV with low drag and don't get the ICE inefficiency penalty.
A PHEV in HEV mode, is still a hybrid. A hybrid is not quite regular. *note)

All normal cars are more fuel efficient (consumption relative to distance) below 120 km/h than above, nothing special for a PHEV, except when going EV (zero fuel). I go up to 130 km/h EV mode, and it can even go 150, but it becomes harder, depending on need to accelerate a bit or uphill.

The battery charge can be used to reduce the fuel consumption at any speed, as the electric motor doesn't have lower efficiency at load, as far as I know.

But where I agree completely, is when it comes to driving style and "tactics". The best approach is probably to either drive completely and constantly EV in EV mode, or switch to HEV and use rest of the charge later, when possible. If your driving style, including speed(s), in EV mode, is so that the ICE has to kick in now and then, or even quite often, it's probably inefficient.

So yes, going fast, like over 120 or 130 km/h when not being able to maintain constant speed and reasonably flat, HEV mode should be considered, but only to the extent that you actually are sure to be able to use all the available charge before next charge up. For 100 km/h I can go uphill at constant speed, or, on flat, reduce to 80 or 90, then easily go back up to 100 without help of engine.

That the PHEV is a bit heavier than the plain hybrid dosn't mean anything at constant speeds. Friction is about the same, and drag is exactly the same. For acceleration and uphill it's a burden, but weight also helps regeneration at the other end.

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*note) A hybrid can
1. Take advantage of an Atkinson cycle engine, since electric motor can take care of the low speed torque (Atkinsons are not good at that)
2. Use a double clutch automatic instead of a CVT, which I believe is less efficient, and car is still smooth for city driving
3. Avoid a larger engine for top power, as electric can supplement it
4. Use regeneration instead of the waste of braking by pure friction
 
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No matter how i drive my ioniq hybrid sel i average 60 mpg per tankful for all miles driven
I calculate all miles driven, divided by gasoline added
 

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No matter how i drive my ioniq hybrid sel i average 60 mpg per tankful for all miles driven
I calculate all miles driven, divided by gasoline added
Meaningless post without knowing your location. Are you talking US mpg or UK mpg?

Please add your location to your user profile under tools - user cp.
 
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