HIGH OIL CONSUMPTION
From Jerry Swartz (jsw7211963@aol.com),
According to the logs, my engine was topped 6-30-91. Cylinders (steel) honed, new rings, valves ground, etc. Tac time then 196.18. Ramerth informed me that he then flew it two hours with mineral oil, pickeled it, and it sat that way until I bought it. It was then taken to Marshall for the annual. The mechanic and I talked many times while it was there about the condition of the engine. He claimed he borescoped it and the cylinders were o.k. Compressions according to him and the logs were (as of 8-14-98) #1 66/80, #2 77/80, #3 76/80, #4 68/80, #5 74/80, and #6 72/80. The mech suggested Aero Shell 15/50 (black bottle) and according to the work order 8 qts were put in. After it arrived here, I checked the oil and it was on seven. I have now flown it l ½ hrs of touch and goes and it is on 6. So, if it were indeed on 8 when it left Marshall, 3 ½ hrs later it has used 2 qts of 15/50. I know for sure that the reading on the dip stick has gone from 7 to 6 in a little over an hour of on and off the throttle flying. So, not being used to steel cylinders, what would you think about the possibility of the consumption getting better, or do you think there is something that should be addressed now?? Stacks are not oily, and the belly is clean. Tac time now is 201.71, so there is about 5 hrs and 30 minutes on the engine since top. Noticed that the last Swift chat session on the net brought up some pretty high oil consumption conversation. My last two engines were 90 Continentals with chrome cylinders, (fresh tops) and they used very little oil. HELP!!!!

Jerry,
Several things come to mind. It was not run long enough after the top to get it broken in. Then, I have no way of knowing how good the cyl walls are. If they have no taper, it should break in quickly. If they are worn, but within service limits, it may take more time. If they are near or over service limits, they never will break in.You mentioned the compression readings. Is that all ring leakage? Assuming its all ring leakage, the rings are either not seated, or worn out. (many rings get worn out in the “breakin” stage) Turn the prop thru by hand (with mixture pulled, throttle closed, mags “off”) have somone listen at the exhaust stacks. hissing indicates a leaky exhaust valve. Pull the air filter, hissing there indicates a leaky intake vave.You can run it with the Shell 15/50, but it won’t break in with that oil. Run it at 7 qts. An O-300 often throws out the 1st qt. If you feel it is not broken in, drain the oil, get some mineral oil like Aeroshell 65, SAE 30, add 6 qts, note the reading on the dipstick, run it to circulate the oil and get another reading. You may have a 172 dipstick installed (non-taildraggger) If it reads 6 qts, then add 1 qt of Marvel Mystery Oil (cool weather only, it thins the oil) With it reading 7 qts, fly it long enough to get a handle on the oil consumption. (At least 5 hours) Don’t let the quanity get below 5 qts. If its taking oil after 5 hrs, you can live with it, or use the “kill or cure” method. Add another qt of Mystery Oil. and take it out and fly at high power. 25” MP for a hour or so. The ambient temps must be below 70 deg, and the engine temps must be monitored, don’t exceed 500 degrees cyl head temp, or much over 200 F oil temp. If the oil gets black it may be from blowby, change it when it gets black. You can save that 15/50 in a clean container and re-install it after you do this. Eventually its decision time, what can you live with?

If the consumption is a little high, but say less than a qt in 2 hrs, you might try continueing using mineral oil with the hope of further break in. If one cylinder is taking oil, evidenced by a oily exhaust stack or oily plug, you might have a broken ring.

Jim Montague