Citroen XM 2.5 turbo diesel fuel economy

Fuel economy on a run from Manchester to cairnryan. Speeds varied between 60-70 where allowed and as low as 30 thru some roadworks.
Running on a veg/engine oil/diesel/petrol mix (petrol=.5-1litre per tank, diesel=2litres max per tank, engine oil=4litres max per tank and the rest is svo