1994 GMC Suburban 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 not coveredby your warranty. is 6-24