Oil is Delvac 5w40, oil before was Kendal (forget the weight)
COMPONENT ENGINE MADE BY GMC
MODEL 2500HD SERIAL#
OIL BRAND DELVAC SAE GRADE 5W40 NORMAL = N, ABNORMAL = A, DIAGNOSIS: NORMAL WEAR RATES, ENGINE AND OIL CONDITION APPEAR OK. NO EVIDENCE OF ABNORMAL LEVELS OF CONTAMINATES PRESENT AS...