ok well, when im on the highway i usually try to stay at about 120km/h which is about 3,000rpm, but if im in speeding traffic or the fast like i kick it up to about 150km/h and thats about 4,000rpm...question is, does it matter if im driving at 4,000rpm constintly and whats to high to be regularly driving at? i have a D16Y7 ..thanks

 

I wouldn't go much higher than 4k for a long freeway trip or something like that. But it'll be fine.

 

is it just cause the ex tranny has such a close ratio?

 

as long as you got good oil and cooling system,high rpm highway driving is actually good for a healthy engine.