50 MPGe - What that really means

Chris Hall

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I have read articles and viewed YouTube videos that are conveying incorrect information about MPGe. I just watched a video on YouTube that claimed the Wrangler 4XE can achieve the same gas mileage as a Prius due to believing that it will achieve 50MPG. While the engineers at Jeep are awesome, they are bound to the same laws of physics and thermodynamics that the engineers at Toyota have to abide by. Just so no one misunderstands, Jeep has never claimed that the Wrangler 4XE will get 50MPG. The 50MPGe rating on the 4XE information is a rating of the vehicle when in electric mode. It is not a combination rating of gas and electric, it is not a hybrid rating. It is the efficiency rating while in electric mode.

I would hate for someone to buy one of these amazing Jeeps thinking it was going to get 50mpg. The misunderstanding about MPGe is leading to a lot of bad reporting that could cause people to be very disappointed in the end.

https://www.cashcarsbuyer.com/what-...lWlXf4aXYBI97BfTNsG3PdYP-v9ZwNbp36vOkIBdlb-8#





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Sboden

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I'll be happy to get diesel gas mileage when out of full electric. Many of my drives are such that electric will make up most if not all of it, so better than diesel in those cases.
 

beaups

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I'll be happy to get diesel gas mileage when out of full electric. Many of my drives are such that electric will make up most if not all of it, so better than diesel in those cases.
Why would it be any better than gas MPG once you’re out of juice?
 
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Chris Hall

Chris Hall

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Why would it be any better than gas MPG once you’re out of juice?
That's a great question. When the vehicle reaches the end of the electric only range, it will fall back to hybrid mode. Naturally, it depends on how the vehicle is being operated but around town there will be opportunities for regenerative braking to put a little power back in the battery. That will allow hybrid operation which should improve gas milage. I'm curious about highway use and if the vehicle will perform a little better or about the same as a standard gas model. The hybrid system adds weight which makes me wonder if it will be about a break even in the end as far as gas milage goes.
 

beaups

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That's a great question. When the vehicle reaches the end of the electric only range, it will fall back to hybrid mode. Naturally, it depends on how the vehicle is being operated but around town there will be opportunities for regenerative braking to put a little power back in the battery. That will allow hybrid operation which should improve gas milage. I'm curious about highway use and if the vehicle will perform a little better or about the same as a standard gas model. The hybrid system adds weight which makes me wonder if it will be about a break even in the end as far as gas milage goes.
I would think (but am no means an authority here) that the highway mpg would be lower than ICE model when the battery is fully depleted since the ICE engine is working to recharge the battery pack and, yes, the weight penalty. Guess we will see.
 
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Chris Hall

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I would think (but am no means an authority here) that the highway mpg would be lower than ICE model when the battery is fully depleted since the ICE engine is working to recharge the battery pack and, yes, the weight penalty. Guess we will see.
I'm curious too. That's one of the unknowns. But there is someone with one of the early test Wrangler 4XEs plugging in some numbers on Fuelly that look really good. What we don't know is how it's being used. It's getting in the upper 20's. I think it's safe to assume since it's one of the early test units that he's either in Northern Ohio or Michigan. Since PHEVs and EVs are impacted by the cold, I would say 27MPG is pretty awesome.
https://www.fuelly.com/car/jeep/wra...Uhbx_KnwddrQFFKARK1w9UbkWGbhFolwnjiSghyV2us8M
 

Demonic

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I would think (but am no means an authority here) that the highway mpg would be lower than ICE model when the battery is fully depleted since the ICE engine is working to recharge the battery pack and, yes, the weight penalty. Guess we will see.
Initially perhaps, but much of the regeneration comes from the braking and coasting. Remember brakes are energy converters. Every time you come to a stop from 50mph, you're converting the momentum of a 2 ton mass traveling 50mph into heat energy (grant it that's an oversimplification). The hybrid drivetrain converts a portion of that energy back into electricity instead of heat, recharging the battery.

Think of a non-plug-in prius. Every time the car slows down the battery is being recharged and that energy is then being used again when needed. There seems to be a misconception of the forum that the way a phev works is that it runs as a battery powered car and then when the battery is depleted it goes clunk and turns into a regular gas car. Even if you never plug the car in or run on all-electric mode, the vehicle will still behave like a hybrid.
 

calemasters

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Why would it be any better than gas MPG once you’re out of juice?
When the batteries discharge down to 10 - 20% and your running on fossil fuel, the battery pack and electric motor becomes a burden.
 
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Chris Hall

Chris Hall

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Initially perhaps, but much of the regeneration comes from the braking and coasting. Remember brakes are energy converters. Every time you come to a stop from 50mph, you're converting the momentum of a 2 ton mass traveling 50mph into heat energy (grant it that's an oversimplification). The hybrid drivetrain converts a portion of that energy back into electricity instead of heat, recharging the battery.

Think of a non-plug-in prius. Every time the car slows down the battery is being recharged and that energy is then being used again when needed. There seems to be a misconception of the forum that the way a phev works is that it runs as a battery powered car and then when the battery is depleted it goes clunk and turns into a regular gas car. Even if you never plug the car in or run on all-electric mode, the vehicle will still behave like a hybrid.
GREAT explanation.
Here's a good article that dives in to it.
https://electrek.co/2018/04/24/regenerative-braking-how-it-works/
 
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Chris Hall

Chris Hall

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When the batteries discharge down to 10 - 20% and your running on fossil fuel, the battery pack and electric motor becomes a burden.
See what @Demonic wrote up above. He explains it well.
 

VNT

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Well with 375 HP combined, I can see a lot of spirited drivers hammering these things which will negate the increase, expect a ton of these folks migrating to this section bitching about gas mileage.

In my 392 SRT if I keep my foot out of it on the highway on long trips, ie do about 65 I can easily get 27 mpg, measured on miles per gallons consume, but only avg 21 mpg overall.
 

hybrid3.0

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In E Selec 'electric only mode', you can travel approximately 25 miles without starting the engine, so you could technically never run the gas engine and operate the vehicle for short distances on electric only indefinitely as long as you have access to charging. Depending on your electric utility rates, preferential EV programs or overnight charging rates (charging can be scheduled to run on the Jeep electric pages to take advantage of these rates), this could be a huge savings. My understanding is even in E Selec, there is programming to run the engine periodically as gas engines don't like to sit unused but need to circulate oil, coolant, fuel etc... periodically to maintain a good state of operation.

Worst case hypothetical scenario; completely depleted battery at the start of a 600 mile one day trip on the interstate going 70+mph. I suspect in this case you would get worse overall MPG rating than a standard 2.0L turbo engine-only Wrangler as you are carrying 600+(?) lbs more weight and recharging the battery pack. In this scenario the 3.0L diesel would be most efficient. Part of the fun of owning a vehicle like the 4xe is understanding its strengths and weaknesses and using it accordingly.
 

dudemind

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There's a little too much skepticism and misunderstanding about how well regenerative braking works. While I can't speak for the 4xe specifically, the truth is that it works pretty damn well in most hybrids. Even when cruising on the highway, the slight changes in speed will result in a surprising amount of energy being returned to the battery every time you need to let off the gas, even a little bit. Even when driving in cruise control, the slight changes in engine output as the engine works/relaxes over nearly-imperceptible changes in grade will result in some return back to the battery. You absolutely do not need to be riding the brakes in CA rush-hour traffic to benefit from some energy regeneration. The 4xe isn't going to turn into a fuel-hungry beast hauling a 600lb brick just because you're on an open highway.

One must also consider that long stretches of uninterrupted, dead-steady-speed highway driving are when internal combustion engines are at their most fuel efficient anyway, making a full-drain scenario on the hybrid battery that much less of a concern.

Now, if you could contrive a scenario where you are legitimately staying flat or increasing the application on the accelerator pedal continuously, sure, you'll eventually run out of juice. But unless you've got a very long and traffic-free hill to climb every single day, you're not going to running out of hybrid assist power as often as you might think.
 

Oilburner

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Jeep says the 4xe has a range of 'almost' 400 miles, let's call it 395 miles.
We know it can travel 25 miles on electricity alone, that leaves a range of 370 miles.
Pretty sure I read it has a 17.2 gal fuel tank, so I would expect the hybrid system to average around 21.5 mpg best- case scenario.
AGREE the whole 'MPGe' thing is Very misleading at best (deceptive marketing more likely)
 
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