Mitsubishi Outlander Plug-in Hybrid Electric Vehicle Forum

Ran a little experiment today on my commute prompted by a post in another thread (which I can't find now!).

For the last 50,000 miles in my 14 plate, I have religiously run in Eco mode, believing this to improve EV range and MPG. But my 1 day experiment has got me doubting that logic.

Here are the stats according to PHEV Watchdog app for the same journey, same route:

In Eco mode (4 Feb):
Distance: 229km
Economy: 10.9 litres of fuel (4.8l/100km [58.9 mpg])
Average speed: 67.5 km/h

In normal mode (11 Feb)
Distance: 229km
Economy: 9.18 litres fuel (4.0l/100km [70.6 mpg])
Average speed: 71.6 km/h

In both cases, the car started with 100% charge and I did a rapid charge to 80% mid journey.

What caught my initial attention was that outward portion of the journey clocked at over 80mpg on the MMC, which I have never got close to on this run, even during summer days at temperatures of 20c+ (today was around 7c).

Has anyone seen anything similar? Just wondering if this is a bit of a freak result, but also wondering if, when in 'Normal' mood, the car accelerates quicker and actually uses less energy than Eco.

I will, of course, try and repeat this tomorrow on the commute to see if I should just be "Normal"!

on a flat road B0 coasting will pay of especially at higher speeds . But in town city / or on slope D driving is better. One can't compare these are tools , use as required

I actually have a whole routine mapped out for this journey - when to hit charge (vs using electric for uphills), when to come out of cruise and drop to B0. There's one downhill section where I knock off the 62mph cruise at the top of the hill, B0, off all pedals and I get to 70mph at the bottom. On a good day I can coast for 1 mile before it's slowed back to 62mph again!

You can coast in B5 as well. And if you choose to use regen in B5, you can harvest much more power, so wastes less power heating up brake disks if you need to slow down.

Single journeys can throw up many anomalies, especially sped and temperature, so comparing single journeys only gives an indication, not a true picture. You'd need to alternate for several journeys before you can claim a pattern. Plus I don't believe the on-screen mpg at all - it seems to be pretty random when measured against actual fuel used vs distance.

You say you use CC, but I'm not sure how that reacts when accelerating back up to speed in Eco. I use the ACC on ours and it accelerates significantly more slowly in Eco. So you might be accelerating longer and cruising less in Eco; but heaven only knows if that's overall more or less fuel-efficient overall

Maybe the 4th of Feb was colder then on 11th

I don't see why Eco mode should cause worst fuel economy

Was the cabin heater started ? If yes ... did you run electric heater in the beginning of the trip, so with ICE off ?

PS: 229km at 71km/h .. you must have lot of patience ... speeding up a bit might cost more fuel, but also save 1h or more of "life"

So, this is going to be anecdotal, because this trip is an out + back commute combining morning plus early evening. There *might* have been a few degrees in it, but not sufficient to account for the difference in efficiency (IMHO). Heating / pre-heating was not used on either trip.



This commute is approx 40 miles (65km) motorway / dual carriage; 12 miles (19km) single carriageway and the remaining 8 miles (13km) city roads (same on the way back, funnily enough!). The inner city section can take 30 to 40 mins on a morning, thus reducing overall average. However, I have been experimenting a lot with increased speed vs time saved vs extra fuel taken. On the 40 mile section of motorway, travelling at 70 mph whenever possible, average speed increases to about 58mph for that section, vs 54mph when cruising at 60mph. On this section of motorway, that equates to approx 7 minute time gain. I can't recall the exact figures, but I seem to recall that the cost of extra fuel was about £2 for that increase in cruising speed which, in my book, is not worth the extra 7 mins!

To check my figures, I have repeated this 'style' of drive yesterday and today and am seeing between 5 mpg and 10 mpg difference between Eco and Normal running.

I am going to really put this to the test in about a weeks time when I head to France, a trip of about 1200kms, a trip I have done many times and so can compare.

I haven't measured anything, but I have a feeling that ECO is mainly aimed for short distance. I'll try to explain my thinking..

One liter of gasoline contains 9kWh of energy.. About the same amount that's inside PHEV's battery! However, ICE has an efficiency of about 20%, which means that for one liter of gas, it can only produce about 2kWh of power moving the car! Rest is wasted as heat. However, if the car interior is cold, big amount of this "wasted heat" can be used to heat the interior! So for one liter of gas, you get 2kWh of car moving and perhaps 5kWh of "free" heat.

In ECO mode, car tries to heat the interior with the electric heater to minimize ICE usage. But this will drain the battery, and eventually ICE will start. At this point, interior will already be warm, and all the "free" ICE heat will go to waste in car radiator.

So... In cold weather and long distance, I think it's most economical to fire up ICE right at the start, where excess heat can be used to warm the car. When the car has heated enough, you can switch to EV and you don't need to use electric heater, which will give you better electric range.

ECO is good if you are driving so short distance that you can go full EV.

I'm not sure that's true. If I don't have the heater controls set to minimum (15°C) and the outside temperature is sufficiently cold, the engine will start as soon as the car is switched on, irrespective of the ECO setting. ECO definitely changes the response of the accelerator, so you have to press it further to get the same amount of power from the car. Other than that, I haven't noticed any differences (but that certainly doesn't mean they don't exist).

There is (as long-term readers of the forum will know) a 'magic' black box from V-Tech that can turn the ECO button into a pure EV button. But it costs €236, which means it would take me (with my driving pattern) about 10 years to recover the cost in petrol savings. New models of the car have a real EV button built in, but they still have the ECO button as well (AFAIK).

Now it is more clear

229km ... I did assume this was a single trip mainly on motorway

But in fact you have 114+114 km

Based on low fuel consumption .. I assume the car get charged also at destination ... so we are looking at 114km drive after a full charge

I'm wondering if you are using charge and/or save in the motorway

As mention by Zuikkis ... the only reason why Eco mode could be less efficient is due to using electric heating vs "petrol" heating

So it would be important to know if you start warming up the cabin while driving in EV mode, or like I do ... I pre-heat the car, and I don't use cabin heating until I will fire up the ICE (in case of a long trip)

Correct - there is a recharge in the middle of the trip so can effectively be consider two trips in one - however, on the outward journey the first 20 miles drop from 300m elevation to around 20m. In normal conditions, I have observed an approximate 10mpg difference between the two legs.

So, I typically use charge on uphill stretches which increases overall efficiency, there's a couple of brutal hills in the first 20 mile section and a couple of long drags on the motorway. In this way, I can stretch the full charge on the outbound (estimated 28 mile range on MMC) to - at best, the 43 mile mark with fuel use at 90mpg. The one time I just let the car do its own thing on the outbound, the full charge lasted around 16 miles (don't know what the mpg was at the 43 mile mark).

On really cold days, I have used pre-heat, but rarely. Secondly, if it is too cold I will use seat heater until I kick on the ICE and then I switch the heating on during those sections! I have to add at this point, I only do this when I am on my own, couldn't get away with such frugal use of heat with OH in the car!


With all that said, I haven't changed this behaviour bewteen Eco and Normal, used exactly the same technique's. Another observation, I will need to refuel today and I will be hitting around 550 miles from the previous full tank - where typically I get 400 to 430. FWIW, filled up at Sainsbury's before (normal unleaded) - I sometimes wonder if some fuels are better than others.

My real test will be next week on a trip to France as there will be at least one section where I need to fill up and drive in standard hybrid mode for the entire tank without an external charging. The best I have done this in the past (on Eco) is about 325 miles on the tank. Plus, today the car gets a service (90,000 miles on the clock) so see if that changes anything.


One thing I have learnt from driving the Outlander is that you can't determine a 'normal' - in that there's so many variables as to the efficiency you get. Temperature, wind direction, wet vs dry roads, average speed, SoC at start of journey, car load, etc, etc. Which, in my view, makes it fun to try and get the best efficiency possible!! Well, having driven nearly 50,000 miles in a little over 18 months, it keeps me amused!