I had the same problem. I put new guide seals in but that didn't help. I switched to 20w-50 and it slowed to an acceptable qt/1200 miles. I had my spark plugs read and they showed some detonation that could be caused by the oil. It was suggested to use synthetic cause it doesn't burn, and stick to premium gas.
I've heard about de-carbonizing on this site. Do a search for info on it. If it has been carboned up by old people driving habits it may help you.
5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)