GMC 1994 Yukon Owner's Manual page 270

What Kind of Oil to Use
Look for these two things:
0
CF-4/SH
C F 4 S H is the best oil for your vehicle. However, if you can not find
CF-4/SH oil, you may use CF-4/SG or CE/SH or CE/SG oil.
These may be listed as shown or in reverse order, for example
SHKF-4. Other letters may also be listed, such as SH/CD, CE, CF-4.
These letters show American Petroleum Institute (API) levels of
quality.
NOTICE:
If you use oils that don't have these designations, you can cause
engine damage which is not covered by your warranty.
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