Driving use and style also make a huge difference. I only use mine for long distance M-Way trips and it never gets used for short urban trips apart from getting to and from the motorway. The cumulative effects of driving faster than 75mph ( actual) on tyres with a high rolling resistance very much will kill your economy. See how you get on with better tyres but if you are doing a lot of short trips and ‘enjoying’ the power of the V8 I would think 20mpg is a reasonable expectation to be honest. 2012 TDV8 Vogue (L322)

So the latest update on this.

I finally corrected my tyre sizes and my speedo now matches what my gps app says +- mph.
I then travelled the same 2 hours mostly motorway journey I did last week.

Before I managed 26mpg travelling at an apparent 70 mph, but was actually more like 77 mph.

This time I was travelling an actual 70 mph, and managed a new high score of 30mpg

So that increase will partly sowing an improvement due to the more accurate mpg the car believes it is doing, and partly the 7 mph less and the drag reduction.

I need to drive with a few tanks of fuel to see how the reported mpg compares to the actual mpg and will update in due course. My expectation is that will still be near 20mpg as before… Currently driving: 2012 L322 SE Overfinch 4.4 tdv8

Past rides:
2014 Audi Q7 3.0d (good riddance)
2010 L322 Autobiography 5.0 Supercharged
2011 L320 HSE 3.0 sdv6
2014 Jaguar XF-RS 5.0 supercharged
2007 BMW 535D
2005 Mini Cooper S

https://www.fullfatrr.com/forum/topic59478.html

I’ve been spending some time on this recently and have made some progress.

Firstly the tyre size correction has helped with the MPG displayed “looking better” than before. I was getting 22mpg before, and with the correct tyre size it reported 26mpg.
These comparisons were made on an easily repeatable journey where the only real difference between them would be the outside temperature.

As mentioned before, i have also had my EGR disabled and blanked. This has given me another 4mpg on my car, and drastically improved throttle response! My car now reports 30mpg for typical driving, with a “low” of 28 with a more heavy rough foot! Brimming the tank and calculating the mpg now shows i am doing an actual 26mpg. More time is needed to get a truer reflection of actual mpg of course…

Things have certainly improved, and i think the next item that will make a difference are the tyres. Swapping for a decent brand with less noise / drag should make a different. Even if only by a few mpg… Currently driving: 2012 L322 SE Overfinch 4.4 tdv8

Past rides:
2014 Audi Q7 3.0d (good riddance)
2010 L322 Autobiography 5.0 Supercharged
2011 L320 HSE 3.0 sdv6
2014 Jaguar XF-RS 5.0 supercharged
2007 BMW 535D
2005 Mini Cooper S

https://www.fullfatrr.com/forum/topic59478.html