Presently I own a 1995 Nissan Hardbody 4x4 K/C A/T truck with 66000 miles and a 1998 Infinity QX4 4x4 with 45000 miles. Both vehicles are maintained per dealer service recommendations. The oil and filter are changed in both every 3 months or 3000 miles WCF althogh Nissan/ Infinity same company state every 3 months or every 3750 miles. I was using the dealer oil QS 10w30 but changed over to Castrol the last oil change.Both vehicles get new Nissan oil filters at each oil change. Both vehicles are subject to normal driving, no off roading or heavy hauling. Any opinions on what type of oil I should use?