Hello.
I had the same problem on the v8 19913.6
After disassembly of the engine I have detected, that a layer NiSi
on walls of cylinders has wear and actually rings work on aluminium.
I have made pig-iron sleeves on one of our factories and have put rings the Shuttle.
The problem with an oil consumption has decreased half.
It is necessary to discriminate on color of a smoke that occurs in the engine.
If the smoke black also is manifested on the big revolutions and at a sharp set of speed
These are failures of a fuel system.
Injectors , a lambda probe. Thus the fuel consumption under condition of quiet driving practically does not increase.
But, because spray jets pour there is a dilution of oil,
And its consumption considerably increases (1.5 litres for 1000 kilometres)
If a smoke grey it is the fastest than a ring or seals of valves. For straightening preliminary treatment of this failure
It is necessary to produce indication of a compression in the engine. After indication it is necessary to fill in the cylinder of 20-30 milliliters of a motor oil and to repeat indications
If the compression increases, rings in the order, if is not present, repair of the engine is necessary.
At replacement of seals of valves it is necessary to produce recovery of barrels of valves,
Otherwise replacement of seals will not solve a problem of an oil consumption.
I used for this purpose the tool of American firm NEWAY. The big role is played also with type of oil.
This engine is not intended for work on synthetic oil when it designed such oil yet was not.
I use to a semy synthetics Castrol 10w30/ After all 150 gramme listed an oil consumption on 1000 kilometres.
Fuel consumption of 16 litres in city and 10 litres behind city at average speed of 140-160 k/h.
That's all, that I would like to tell, it can to somebody will help.
Dmitry

p.s. Excuse for my English