V90 D4 MPG Improvement
 

Hi All,

Just wanted to share this as it is rather amazing improvement based simply upon the outside temperature effect, or so I'm told! I've had my V90 now for almost 5 months - still love it! But I have struggled to get the fuel consumption figure above 42 mpg through the winter time! But today same trip commuting with outside temperature reaching 18 C, I managed to record a not too shabby 54 mpg! That is an absolute massive change for the same trip! Remember its a bank holiday so the traffic was actually worse than normal!

A 28% improvement in fuel consumption!

Amazed!

The increase in traffic and probable slower progress surely had more to do with it than air temperature.
My Honda consistently does between 42 and 44 mpg on a long journey, Summer and Winter. Except once when I travelled from near Felixtow up the M6 and over to Shrewsbury and across to Aberystwyth in very heavy holiday traffic. This kept speed on the motorways down to no more than 50mph for long stretches and seldom over 60, more often down to 30 and 40. Was quite tiring but it did yield 50mpg, a figure I've not got within 5mpg of in three years since.

I am pretty OCD about economy and lots of things make a difference other than the obvious heavy feet and traffic jams.

It is true that colder temperatures affect diesel and you’ll always get worse numbers in the winter months. It’s amazing just how much difference wind makes to (I live in N Wales therefore an expert on head and tail winds!!!) - a decent tailwind can be up to 5mpgs better than a headwind (just go cycling in a strong wind and see what i mean).

I have a very friendly economy commute of 42 miles of dual carraigeway and managed 70.6mpgs (according to the car so not that accurate) the other day with about a 20kt tailwind and 10 degs outside air temp. Similar conditions going the other way (about 2 degs cooler) was calculated at about 63mpgs.

Increasing speed above 60-65mph has a huge impact on economy too.

With outside temp going up my foot becomes heavier and my mpg usually drops comes springtime.. :rolleyes:

Cold air is more dense which allows more air/fuel into engine and power, combine this with the use of heated seats, heated front and rear screens and mirrors in winter and more use of main lights and economy will be effected.
It takes a lot of energy to turn an alternator when providing a lot of electrical power.

Economy was up again today - 48mpg but light traffic. I read in the owner manual that the official fuel economy ratings were obtained in the comfort setting - does anyone know how much of an impact running in eco- or dynamic- would have relative to the standard setting?

I have not noticed any difference in eco, comfort or dynamic mode to fuel economy but I tend to drive in the same manner in all modes, if I were to use dynamic enthusiastically I would expect a lower economy but that would be the same driving like that in any mode.

I have driven the same 48 mile route in all three modes and mpg was near enough the same in each mode. I was using PA2 at 60 mph for half the journey on dual carriage-way and ACC when possible the rest of the time at 55 mph on each trip and averaged ~ 43 mpg in my XC90.

Interesting - I noticed that when using pilot assist or ACC in eco- there is no "coasting" I wondered how much of an impact coasting could make!?

I believe that coasting in Eco mode is likely to actually use more fuel than when on the over-run with gears engaged in other modes. Not much but certainly not more economical.

Logically, when a modern petrol and Diesel engines are on the over-run, compression braking, no fuel whatsoever is injected. However when coasting, the engine must inject fuel to maintain idle speed, otherwise the engine would stop.

It's been commented on quite a lot in the old xc60 board that the VEA engines are quite sensitive to outside temp and run significantly more efficiently when it's hot out.