https://www.pilotsofamerica.com/community/threads/smoke.130894/#post-3051900 Above is the background. Today flying again for the last time with CFI and oil gets on windshield. Mechanic looks at engine, says I need to break it down for overhaul or trade out for zero time ("Through bolt and top of the engine casehalf" is where the leak was). 1974 Cessna 172 M. Engine time is 2000 ish, top end 100-150 hrs. O-320 E2D placed in 1997. My current useful load is 777#. I think I will keep the Powerflo exhaust if I keep this engine size. I've been told my options are to overhaul it, mechanic will take off engine, mail out parts, get stuff back, reassemble. 80 hours labor @$95 each He suggested 6 weeks, $20-22K. Exchange engines, 40 hours labor @$95, 10 weeks to get it in from one shop in state, $30K. We lost 1/2 quart of fuel (NO NOT FUEL< IT WAS OIL) today. Mechanic initially said plane safe to fly 20 minutes to his airport. CFI said this could be an NTSB report waiting to happen. So my questions: 1. $28K my engine or $34K exchange and why? 2. Do you know of other shops with in stock exchange engines? I want to fly... 3. Would you fly this plane to destination 20 min in air? 4. What about 180 HP engine upgrade to increase useful load? I guess it would be stock exhaust then. What else? Thanks, I guess.