Best economy for motorway drive

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Togfather

Member
Joined
Jun 4, 2021
Messages
10
Location
Scotland
Hello.

I am about to embark on a long motorway drive, and will be travelling at a steady 60mph. Once the battery is depleted, which of the following will give me the best MPG economy? (all driving will be in economy mode and cruise control will be used).

A) Leave the car to sort out the balance between charging and driving without any driver input.

B) Engage charge mode and switch charge mode off when battery is full. Then repeat when battery is depleted again.

Many thanks for any help and figures anyone can supply.
 
What I do (and I'll suggest this only to you since it seems to work for me) is to initially let the battery run down to 50%. Then I put it on SAVE. When I get to a built up area I turn SAVE off and re-engage when I hit the fast road again. This means that, depending on the mix of environments, I eventually drain the battery. At that point I don't worry, I just drive it. Depending on the number of hills, the number of times you speed up to pass, the temperature and the weight of your foot ... you should get a usage of around 6.x/100 km. I've never seen 5.x ... but we live in the mountains with lots of hills. Increasing fuel usage is easily achieved by driving faster :)
 
Hello. Thank you for answering, but my question still stands. I don't want to save any battery for city driving. I just want to know which option is the most economical.

Best wishes

Tog :)
 
I'm all but certain that A) will yield better results in general. Charging with the generator takes a long time and consumes fuel constantly, and I'd be surprised if you can make that up when you switch to battery.

That said, one thing I experimented with on a recent drive was charging before a planned fuel stop, to convert some reserve fuel to electricity and increase the range on the next leg. I'm not sure how well that worked out, but part of the fun of this car is experimenting with things like this!
 
Togfather said:
the best MPG economy? (all driving will be in economy mode and cruise control will be used).

A) Leave the car to sort out the balance between charging and driving without any driver input.

B) Engage charge mode and switch charge mode off when battery is full. Then repeat when battery is depleted again.

Many thanks for any help and figures anyone can supply.

There was considerable experimentation on using the Charge mode about 5 years ago published on this forum -
https://www.myoutlanderphev.com/forum/viewtopic.php?t=1935
and
https://www.myoutlanderphev.com/forum/viewtopic.php?t=1237

The experiments found a tiny (0.5 litres/100km or less) advantage of actively using Charge mode, but not quite as you say. Charge mode isn't optimal when the battery nears full due to a reduced charge rate (this is why Tesla superchargers slow down > 80% SOC).
 
Option A is equivalent to option B but not charge to full. Charge from 0 to 30-40%. Rinse and repeat.
The goal is to be in parallel mode once the engine is working and low state of charge.
Simply there aren't any other more economical options beside parallel mode once the engine is running. Has to be combined with low state of charge as well.
My test:
https://www.facebook.com/kbpetrov/posts/10218787302894911
 
The PHEV needs a fixed amount of energy to get from A to B. Once the battery is empty, all that energy has to come from the ICE. So the car will have to charge the battery for way more than half the time whatever you do, and saying that using CHRG is less economical than using some other option misses the point of how the car works. Practical tests have shown that using CHRG is less economical when the battery is above 60% full. There is a general consensus that using CHRG when in Parallel mode (above 40mph/60kph) is more economical than when in Series mode at lower speeds. And as mentioned, using CHRG for long periods may be very slightly more economical than letting the car charge itself via the Hysteresis Loop.

To be honest, just putting it in 'D' and leaving it to its own devices is not a bad solution unless you enjoy twiddling the settings during a journey. I've not seen any repeatable tests that show if one way is better than another.
 
ThudnBlundr said:
To be honest, just putting it in 'D' and leaving it to its own devices is not a bad solution unless you enjoy twiddling the settings during a journey. I've not seen any repeatable tests that show if one way is better than another.

If there was a real winner, Mitsubishi would have used it. The only reason you can beat the car is because you have some knowledge of the future of your journey, however even you don't know if accidents or traffic jams will slow you below the parallel hybrid speed.
 
Agreed that there is probably no clear winner when you are taking long trips. In my case, I like to keep the battery at least half charged or so because I never know when I am going to hit bad traffic... and of course, I try to reach home with an empty battery.
 
Fjpod said:
Agreed that there is probably no clear winner when you are taking long trips. In my case, I like to keep the battery at least half charged or so because I never know when I am going to hit bad traffic... and of course, I try to reach home with an empty battery.

+1 :D
 
Hello, and many thanks for the replies.

For those who are interested I did conduct my own tests and the results are as follows:

Starting with an empty battery and driving in eco mode with "charge" activated, then deactivating "charge" when battery more than half full, and re-activating "charge" again when battery empty resulted in a consumption of 38.2 miles per gallon over 200 miles, driven at a steady 59 miles per hour in ACC.

Starting with an empty battery and driving in eco mode for 200 miles, allowing the car to use its automated charging system resulted in 42.3 miles per gallon over 200 miles, driven at a steady 59 miles per hour in ACC.

Best wishes


Tog :)
 
While your willingness to experiment is admirable, unless the driving conditions, weather and geography were identical for both tests, they're fairly meaningless. Plus a sample of one is also notoriously random. On the same drive down from Yorkshire to Cornwall to visit by brother, my consumption has varied between 32 and 45mpg. Admittedly I'm not trying to have a reproducible experiment, but my variation of almost 50% shows how "random" readings can be
 
Thanks for your input, and I agree that there are some variables which cannot be controlled.

However, I did the test in the same direction on the same road on the same day (I drove the journey, drove back, and drove the journey again) and used the ACC for all of the journey, except where traffic required me to slow down, so I believe this was the best test I could perform, short of using a specialised test facility, which I do not have access to.

I am happy to use the results to dictate my driving methods for the future.

Best wishes

Tog :)
 
Togfather said:
I don't want to save any battery for city driving.
Given that I would recommend starting battery fully charged and just cruise ahead in normal mode and ECO on. Once you consider a break, plan to park at a power station for fast load while picking up your coffee. You'd need a parking slot anyway. Why not loading at the same time? Then continue cruising as above. That'll work simply and perfectly.

In case you know the route and want to invest more responsibility to city driving or any kind of slow passages in between. Consider full battery start and driving until the battery is in a low range. Then select Charge mode to collect power for slow driving passages on the route or city driving.

On a really long route it might be interesting to toggle Save and Charge loading to max 60% battery power.

Overall goal is to finish up with an empty battery.

Personally, I'm not using the ECO mode at all and prefer silent e-driving at low speeds.
 
Thanks for your interesting input.

I don't do any city driving and motorway driving is quite rare for me, although I made that trip twice just as an experiment.

I live in the middle of nowhere and my normal driving is to and from a small town around 13 miles away on a bendy rural road, which takes about 35 minutes.

There is a free charging point in the town and I can often drive from there to my home and back again on a single charge, so get amazing MPG with little or no charging cost. I do occasionally charge at home if the charging point in town is busy or if I don't have time to wait.

I drove for 1700 miles with an average of 138 mpg, so this is not only the smoothest car I have ever owned but also the cheapest to run.

I am a very happy bunny indeed :)
 
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