MAULE AEROSPACE TECHNOLOGY, INC.
MAINTENANCE MANUAL
FOR
MT-7-420
9/02
4
Approved Oils: Mixing of approved oils in 250 series engines is permitted only within a given
group number. An oil may be mixed with any other oil in its group. For example, an oil in
Group 23 may be mixed with another brand of oil in Group 23. Refer to the latest revision of
Allison 250-BI7 Engine Operations and Maintenance Manual (Publication 11W2) for ap-
proved oils, paragraph 1-74.
WARNING:
MIXING OF OILS WITHIN AN OIL SERIES BUT NOT IN THE SAME GROUP
IS PERMITTED ONLY IN AN EMERGENCY. USE OF MIXED OILS (OILS
NOT IN THE SAME GROUP) IN AN ENGINE IS LIMITED TO FIVE HOURS
TOTAL RUNNING TIME. ADEQUATE MAINTENANCE RECORDS MUST BE
MAINTAINED TO ENSURE THAT THE FIVE-HOUR LIMIT IS NOT EX-
CEEDED. MIXING OF OILS FROM DIFFERENT SERIES IS NOT PERMIT-
TED.
FAILURE TO COMPLY WITH OIL MIXING RESTRICTIONS CAN RESULT IN ENGINE FAIL-
URE.
