Basically I would like real world expedition vehicle mpg l/100km fuel consumption figures please to help me make the following decision (read below if interested)

Figures preferred for fully loaded with roof rack, tent, awning, kitchen sink on board please.
I have a landrover d2 v8 auto with all this mentioned, plus close to 3000kg (not weighed since donated much unused equip) running standard sized at's tyres.

Worst case on tough piste inc some sand and v rough tracks 13 mpg
Best case (probably with a tailwind) 22mpg
Overall average 7000 miles 16 mpg. 17.7 litres per 100km

Are these figures so bad......? What do you get in your 4x4.

With some considerable streamlining (Alu box on roof protrudes 1ft further than windscreen! Oops) I hope to get this up by 1-2 mpg maybe 3 if I am really lucky and when on decent roads at 50-56 mph. It maybe goes without saying I have to drive with a light foot, currently going over 60 mph brings the figures down!




Background info.

We bought a car to do a one way trip to west africa and then sell. We found a Landrover discovery 2 V8 going for a song and thought why not (no comments yet please!)

Something terrible happened whilst preparing the vehicle and travelling in it, we became emotionally attached! . I went completely overboard on preparing it for a one way trip, spending countless days/ weeks on ebay/ the internet sourcing second hand parts where possible and months fitting and custom building the interior locker system.

So we are in a position I would probably not wish to repeat. I love the d2, not my first choice for harsh climates but it got us to Gambia and back just fine. The car is IMHO beautifully fitted out for living out of long term now and I can't bring myself to sell it (plus not many would want it with the v8!) plus I have already renewed many items on it.
This is one of the smoothest rides you could wish for (OME springs shocks plus air helper bags) its a joy to drive. Did a 14 hour day just yesterday through morocco and Spain. Auto box is surprisingly great on and off road.

Anyway this is my dilemma. Fuel consumption! I got the car cheap, so I saved quite a few quid which goes towards my fuel bill. But as we now want to keep this a few years at least and do some mid range trips.

So do I
1) suck it up and accept higher fuel bills and leave the car as is.
2) get a reputable LPG conversion done so at least in Europe we can get (much) lower fuel bills. (Hugely mixed reports on LPG conversions) The car will be in use in Europe the vast majority of the time apart from odd trip.
3) buy a disco td5 breaking and take all I need off it and change to td5 (fuel consumption reports widely mixed and possibly not hugely better...?)
4) fit 300 tdi engine, (seen it done) enjoy electrical free travelling (would then consider long range trips without support) but loose the refinements. Cruise control is my new favourite toy!
5) fit totally different engine (I can hear the hmmm's with that one already) how about a big diesel lump? Lr with a lc engine???


Thanks in advance
James