Originally Posted By: geissjr
I just purchased a 2015 GMC Sierra. The truck calls for a 0-20 semi synthetic. Should I continue to run the semi synthetic or convert to a full synthetic? I also have PP 5-30 in the garage from my old truck. If I convert to full synthetic would it be ok to use up the 5-30 in the new truck? My guess is the 5-30 synthetic will have similar properties at startup compared to the 0-20 semi synthetic. Thank you for your input.
I dont see any requirement for semi syn in the 2015 owners manual, just a mention of Dexos.
From page 10-11
"Viscosity Grade
Use SAE 0W-20 viscosity grade for
the 5.3L and 6.2L V8 engines. Use
SAE 5W-30 viscosity grade for the
4.3L V6, and 6.0L V8 engines.
Cold Temperature Operation: In an
area of extreme cold, where the
temperature falls below −29 °C
(−20 °F), an SAE 0W-30 oil may be
used in the 4.3L or 6.0L engine. An
oil of this viscosity grade will provide
easier cold starting for the engine at
extremely low temperatures."
From page 11-12
"Engine Oil Use only engine oil meeting the dexos1™ specification of the proper SAE
viscosity grade. Look for the dexos1 approved logo for GM approved
engine oil. See Engine Oil on page 10-11."
Source...
Click here for 2015 GM Owners Manual