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After 2 years of ownership I'm still not sure of the answer to this.

My petrol / electric hybrid has a choice of several driving modes. The default mode is to use electricity only until the batteries are almost exhausted, then to switch to petrol. This is the mode I normally use because I want to minimise the use of petrol, and most of my journeys are less than the 30 mile electric range. There is also a hybrid mode where the car automatically selects the appropriate fuel and switches between them as necessary. I'll ignore the other modes for now (battery saving, GTE etc).

My question is this:- with a full petrol tank and a fully charged battery, which mode gives me the maximum range under normal conditions? Or in other words, is the hybrid mode more fuel efficient than the hybrid mode? In theory the hybrid mode should be slightly more efficient because the car can select the ideal fuel for the speed and conditions, but is it more fuel efficient in practice?

My car is a Golf GTE but the question applies to any hybrid vehicle.
 

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How long is a piece of string?

The answer is different for each hybrid vehicle. I assume you're asking for plug-in hybrids, and I can give you what should be the most efficient approach in a Mitsubishi PHEV, but that is mechanically a very different beast to the GTE or a "self-charging" :mad: hybrid
 

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Agreed, if you have a Regen capability this will work better once %charge has dropped, and if you run on petrol first you will loose any regen capability. For town or start-/stop driving battery is probably best.
 

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Well for most normal driving scenarios, battery only 1st is a better option for efficiency, because it achieves higher miles per kilowatt hour of total fuel energy content while using battery only, and most trips are short so they won’t fully exhaust both the gas tank and battery before he can plug in for recharge. This option gives both higher miles per kilowatt hour and higher miles per gallon.

But he’s asking about a special scenario... which option goes farther with no recharge, fully exhausting the gas tank and battery. He doesn’t specify the driving conditions so the simplest option is to assume constant speed on flat ground (no braking so regen isn’t a factor). With these assumptions, if he uses the battery first, when it runs out the car will automatically recharge the battery, which results in a extra energy converison step (petrol->battery->kinetic rather than petrol->kinetic), and that extra step lowers efficiency, so for longest range at constant speed it makes sense to fully deplete the petrol first, then use the battery, so efficiency won’t be lost converting petrol energy to battery energy then to kinetic.

Edit: he’s actually asking 2 different questions... the subject says “which is the most efficient driving mode for a hybrid?” but the body asks “with a full petrol tank and a fully charged battery, which mode gives me the maximum range under normal conditions?”

The answer to the subject line question is battery only first and the answer to the question in the body of the original post is hybrid first till petrol runs out, then battery only.
 

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the answer to the question in the body of the original post is hybrid first till petrol runs out, then battery only.
What happens to the recuperation on a GTE when the plug in battery is full? So, for example, if on a journey you start with a fully charged HV battery at the top of a steep hill can the gravitational potential energy being released going down the hill be stored over and above the 100% of the plug in storage?
 

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What happens to the recuperation on a GTE when the plug in battery is full? So, for example, if on a journey you start with a fully charged HV battery at the top of a steep hill can the gravitational potential energy being released going down the hill be stored over and above the 100% of the plug in storage?
At constant speed on flat ground there is no hill or recuperation.

He doesn’t specify the driving conditions so the simplest option is to assume constant speed on flat ground
 

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"There are five operating modes that include E-mode, Battery-Hold, Battery-Charge, GTE mode and Hybrid-Auto."

"On the motorway, the Battery-Hold mode uses the petrol engine alone and although adequate, it doesn’t have the oomph of the GTI. However, if you are cruising, it doesn’t really matter."

^So for greatest range at constant speed on flat ground, use battery hold mode 1st until the petrol runs out (no energy from the battery will be used), then travel the remaining miles on E-mode. This avoids converting any petrol energy to battery then to kinetic, which is an extra conversion step. If you do it the other way around, the petrol engine will automatically partially recharge the battery when it runs out, reducing efficiency and therefore range.
 

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Hi Emver, I'm going to challenge and expand a couple of bits - after 4years with my Golf, as the most efficient way to drive a Golf GTE ( or Passat/Skoda/Audi equiv PHEV) is different from other PHEVs.

However the very first miles of an above-GOM-range trip do apply to all PHEVs ----- drive off in eMode/Pure EV so that you drop the battery level ASAP. Unless you live by a motorway slip road your first miles of a trip are going to be junctions / lights / roundabouts and you need the battery level dropping so that you recuperate the energy, and are not losing it as the battery is too full.
In a Golf GTE if you have the gear-lever in B Mode you'll know there is no retard when the battery is full ----- the above is why, as others put here, there's no where for the energy to go. For max efficiency, you want to capture it.

So, drive off in eMode for the first few miles.
Then, and this is for most PHEVs, find some road where the engine would be under gentle constant load for a good few minutes. Summer, 2 or 3, winter 4-5+.
THEN switch to hybrid mode. Don't do it where the car will come to a halt moments later (junctions, lights, roundabouts) --- As with any PHEV when the engine kicks in the first time in a trip, it will run in warm up mode, regardless of the car slowing or stopping ---- very frustrating when you want max efficiency (spelt mpg).
So only go into Hybrid mode when the car will drive nicely for a bit.

Next, be watching the miles left of your trip vs the GOM estimate ( and your own knowledge of how far you can drive in eMode ). When you get to about parity, go back into eMode, using the battery up, aiming to arrive at your destination with 0-1 left on the GOM. This technique ( eMode, Hybrid with a non stopping warm up, stay Hybrid then eMode to empty ) should give you the highest mpg from the unleaded.
I've done 200mile+ trips from out in the sticks to the BigSmog and got 55-60mpg overall including motorway and Waterloo/FleetStreet/Kingscross whilst in London. Bit of button pressing in places, but hey the Golf GTE is such an amazing car compared to what we drove 10+ years back. And not even talked about GTE mode on cross-country early morning routes.

Finally one last difference that is important - again Audit A3 eTron/Passat Skoda PHEVs do this too as far as I am aware but is important to understand.
When the Golf GTE battery gets to 0 miles, and the ICE kicks in , the car attempts to regain the battery back up to 2-3miles. During this time the mpg is pants. Really Really terrible ---- use the trip computer instant mpg readout and you'll see what I mean, whilst you cry. And, it can be ages even on a motorway. ( Bit like using the battery charge mode - they should call it Cry Mode ) .
If your journey is GOM range + 5miles, your mpg at the end is terrible compare with the eMode>Hyrbid>eMode method. If the GOMrange+5miles is your commute, try do-nothing with the buttons for a week, then try the other for every trip the next week ...... I think you'll be surprised. Add it up over a month and it's a reduction in the fuel you need to put in the tank.

Enjoy your car, it really is amazing and my will be replaced with a BEV or Merc A350e. I'm hooked.
 

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If in the constant speed on flat ground scenario hybrid mode results in the battery running out before the petrol tank is depleted, battery hold mode then electric will be more efficient, Or possibly hybrid mode, then battery hold mode when the battery is low, then electric mode. Higher instantaneous miles per gallon in hybrid mode doesn’t help maximize range if the miles per gallon later decreases having to recharge the battery with the gas motor. Braking and recuperating doesn’t help maximize range either because regen braking only has 70% kinetic to kinetic efficiency.
 
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