the 30 synthetic is better for the engine. fuckin hell i've always wanted a z, its gotta be my next car. glad the pump and therm swap was easy, i have to do gymnastics to get to that part of the engine. i'd look into what spark plugs are good for the car if you're thinking of replacing them because they make a massive difference. i use ngk laser iridium, just make sure they're not gonna be too hot and melt shit. also get a spark plug socket so your life is easier. they're $9.
United States