Its not really getting factory MPG's if you are also burning a gallon of oil between fillups. Sounds like worn rings to me.....valve guides would have to be in horrible shape to cause that as diesels do not operate with vacuum and thus do not really have suction to pull much oil past the valve seals....usually.

My OM601 has a fair amount of blowby but uses no oil at all between 5,000 mile changes and still fires up no problem even in negative temps. (as low as -10F last winter)...engine has about 265k on it. Have replaced:
-Timing chain
-Delivery valve seals
-Vac Pump
-Hydraulic Lifters
-Injector Nozzles
-Air Cleaner Bushings and filter
-All belt drive components
-Glow Plugs

If its that worn out at 271k there's a chance earlier in its life that it did not get proper oil changes....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)