i was in walmart and noticed they have castrol gtx in 5w-20 grade so decided with this oil change in my old 1988 honda civic i'm using the newer grade. hopefully it won't cause any damage. i don't think it will and i think it's going to be an improvement. less strain on the crank shaft and pistons. anyone who has any knowledge about the newer oil please let me know. thanks.
-jeff the newer grade of oil is just for that for newer vehicles." you have used it? shoulden"t harm your engine in fact you might even gain a slight increase in gas mileage from the thinner viscosity". however i would not take a chance on my engine. on your next oil change switch back to what the manufacture has called for ;)