A year on and I still haven't found the best solution.
I first put in Millers 5w40 (nanotech) and, assuming it's 1 litre between the max and min marks of the dipstick, I was getting around 600 miles per litre. I ran out of Millers and used various 5w40s from various garages (mostly Shell and Castrol and once Total) and the consumption rate was the same.
After 5000 miles, I have just changed the oil/filter and put in Motul's 300v 10w40 semi-synth which seems to have burned over 1 litre in 400 miles.
Would you suggest I try a semi-synthetic 10w40 next or go straight to 10w60? If so, I know most are synthetic but Valvoline do a semi-synthetic 10w60 - would that help consumption?
I am not a scientist , but it seems that more oil per mile gets burnt on my long motorway journeys (i.e warm engine) rather than short journeys around town (i.e. cold engine) around town, so I'm assuming it's the "40" part of viscosity that is the root of the problem.
If anyone has had similar problems and found a brand and viscosity that gets them down to over 1,000 miles a litre, please let me know.
So frustrating when I look at my CF1 2.0 TS GTV which easily does 2500 miles per litre on 10w40 semi-synthetic!