PIPER COMANCHE SERVICE MANUAL
II - HANDLING AND SERVICING 04/01/09
1C40
2-81. Recommendations for Changing Oil. (Refer to latest revision of Lycoming Service Bulletin No.
480 and Lycoming Service Instruction No. 1014.)
a. Oil Change Intervals.
1. For engines equipped with full-flow oil filters, change the oil and filter each 50 hours of engine
operation or every four months, whichever comes first.
2. For engines relying upon pressure screen filtration alone, change the oil and clean the pressure
and suction screens each 25 hours of engine operation or every four months, whichever comes
first.
b. Ashless Dispersant (Detergent) Oil.
1. With the exception of turbo charged engines, new or newly overhauled engines should be
broken in on straight mineral oil for the first 50 hours of operation, or until oil consumption
has stabilized. Lycoming oil additive P/N LW-16702 may be used. Mineral oil must also be
used following the replacement of one or more cylinders until the oil consumption has
stabilized. Attempting to break-in normally aspirated engines with detergent oil may result in
high oil consumption as the additives in some of these oils can retard the break-in of the piston
rings and cylinder walls.
2. All new or newly overhauled turbo charged engines must be broken in and operated only with
ashless dispersant (detergent) oil.
3. In engines that have been operating on straight mineral oil for several hundred hours, a change
to ashless dispersant oil should be made with a degree of caution, since the cleaning action of
some additive oils will tend to loosen sludge deposits and cause plugged oil passages. When an
engine has been operating on straight mineral oil and is known to be in excessively dirty
condition, the switch to ashless dispersant oil should be deferred until after the engine is
overhauled.
4. When changing from straight mineral oil to ashless dispersant oil, the following precautionary
steps should be taken:
(a) Do not add ashless dispersant oil to straight mineral oil. Drain the straight mineral oil
from the engine and fill with ashless dispersant oil.
(b) Do not operate the engine with ashless dispersant oil longer than five hours before the
first oil change.
(c) Check all oil screens for evidence of sludge or plugging. Change oil every ten hours if
sludge conditions are evident. Resume normal oil drain periods after sludge conditions
improve.
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