GMC 1993 Suburban Owner's Manual page 278

K2543
What Kimd of Oil to Use:
Look for three things:
so
SG must be on the oil container, either by itself or combined with other
quality designations, such as W C C , SGlCD, SF, SG, CC, etc. These
f
you use
oils
that don?
have the "SG" designation:,
yw can:
cause
engine
damage not covered by
your
warranty;'
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