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 wont 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) Dont 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, dont 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
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