800 miles is ok, just not ideal. 500 miles is the threshhold i use for excessive. look at the turbo, they can pass oil out the exhaust. also, if possible during the purchase inspection, get a compression and cylinder leakdown test. it will cost more money, but this way you can see if the block is worn enough to be the cause of the oil consumption. i know the 85-88 b230ts had weak castings, but i've not seen that in the later blocks. good luck, chuck.