Chevrolet 1994 Blazer Owner's Manual page 248

SHorSG
"SH" or "SG" must be on the oil container, either by itself or combined
with other quality designations, such as "SH/CD," "SH, SG, CD,"
"SG/CD," etc. These letters show American Petroleum Institute (API)
levels of quality.
SAE 5W-30
Energy Conserving I1
Oils with these words on the container will help you save fuel.
These three things are usually included in a doughnut shaped logo (symbol)
on most containers. If you cannot find oils with the "starburst" symbol, you
should look for oils with the doughnut shaped symbol, containing the three
things noted above.
NOTICE:
If you use oils that do not have either the "starburst" symbol or
an API SH or SG designation, you can cause engine damage not
covered by your warranty.
GM Goodwrench@ oil (in Canada, GM Engine Oil) meets all the
requirements for your vehicle.
Engine Oil Additives
Don't add anything to your oil. Your GM dealer is ready to advise if you
think something should be added.
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