i have a 1990 5.0 that suddenly started using a quart of oil every 200 miles. no puddles in driveway,no noticable smoke out exhaust.any ideas?

 

Rear main seal probably...in the back of the lower intake...see if theres a bunch of oil...should be all over the bellhousing...also the oil pan gaskets are probably toast...lemme know

 

if its not simply leaking somewhere, might look at one other thing:

after a cold start, do a quick around the block trip, shut off and immediately check oil level...my mark VII head drain holes are sludged up so bad the valvecovers fill with oil, oil level drops way low when cold, after shutdown takes probably a full minute to even get back on the dipstick...rear main leaks a little, so havent driven it in several years now, will rebuild it 'one of these days'...

I would sure imagine with that much oil in the heads that the valve guides would be sucking a LOT of oil...if you see a crazy low level after a brief cold run, might suggest popping the valve covers, poking out the drains and then flushing the motor. if the drains are sludged up, flushing might not work without opening them up with a piece of wire or something...plus while the covers are off, a bunch of sludge could just be scraped out with a screwdriver...