hello Eddy, the volvo 850 fuel consumption is not that bad to be honest, ive got a '96 855, 2.5 10v, and around town i get mpg in the low 20's. the newest car you can afford should be the best but obviously because theyre used cars you have to be careful. full service history is brilliant to have but not essential as a lot of Volvo owners service their own cars. front tyre wear is quite heavy on 850's, so check the tread. check the suspension all round, if its got a tow bar make sure it the suspension doesnt sag on the rear end. turn on the ignition key and check all the lights on the dash come on and go off when the engine is started. check for mayonaise like deposits in the oil filler cap. check the rear oil seals on the engine. make sure the brakes work nicely. i think most, if not all of this is relevant with the phase 1 v70. as for engine size, i think the 2.5 either in its 10v or 20v guise is powerful enough, but the t5 is much more of an animal. i hope this helps, regards cavey