1999 Hyundai Elantra with 2.0L DOHC motor. OCI every 3,000 kms on dino (perhaps a little over-kill, but what the **** ). I usually buy what's on sale from the big brands (Castrol, Pennzoil, QS, Motomaster F1). Currently running Pennzoil dino 5W30 from winter. Next change will be Motomaster F1 dino 10W30 for the summer. Would it be better to stick with one brand, because I rarely have the same oil in the car for 2 oil changes?