2010 5.0 Supercharged.
I used to get around 17mpg until it got serviced at Landrover. Since then I've struggled to get better than 12mpg average. The problem is that the service was early last year so I can't go back and blame them. The only thing that Landrover did other than the service was change a brake light bulb. I don't use it much so initially it didn't bother me but now it's driving me mental. The question is why has this happened. The only other issues since the service have been on one occasion the dash showed a gear box fault which cleared by turning vehicle off and on. The other was a parking brake fault light which cleared after turning it off and on. Both of these issues were just warning lights and did not affect the actual driving. I have read that the Brake light switch can cause many issues with these vehicles but before I start trying random item's can anyone suggest what has caused the issue?

Cheers
Dave

Even though only warning light might be worth getting the codes read, any warm wheels after a run indicating a sticking brake ? 2008 G4 RRSport TDV8 current
2009 TDCi 90 current
2018 Discovery 5 HSE lux current
1994 Dakar current

I haven't noticed any binding from brakes. It's worth checking as may be contributing to a drop in economy. The other thing I noticed was that the idle didn't seem as smooth after the service so there must be a cause to a drop in mpg and slightly rougher idle. The warning lights on 2 occasions may or may not be linked to the issue or just coincidence

Running rough on idle, like the choke is out on an old car ?
Temperature sensor not giving ecu correct signal so thinks it is cold engine and throwing in excess fuel.... maybe! 5.0 Ltr Superchrged RRS2, Chile Red, Sideways out of junctions!
TDV8 HST Stornaway on a 08.. remapped.. now gone and replaced, was a mighty fine car..
4.2 SC First Edition when they first came out, quick car!

When I say rough idle its very faint. The revs are low(normal) and stable but you can feel a very slight movement/shudder in the vehicle. Would diagnostic equipment pick up on a potential temp sensor issue if there are no dash lights showing an issue?

Have you actually measured the drop or are you basing it on what the onboard info. says?

If you don't use the car much is your comparison over a period that predates the cold winter weather. If you're only running it on short trips at this time of year I'd expect the fuel consumption to be worse than before December etc.

Only ever get around 200mls. to the tank full on mine, which works out about 13-14 mpg. on average. Did check once out of curiosity after long run and it showed 17.3 mpg. Have never tried driving like "Miss Daisy" to see what it will actually do though.

Just had a look and currently showing 12.1mpg after a couple of short trips, but wouldn't know for sure how accurate the trip computer really is.

Cheers
Col