I have a 5sp and as most of you know if you are cruising on the highways you are doing about 2.5-3K RPMS for what may be hours at a time. This is of course in 5th gear but I was wondering if this means that it would be safe to just cruise around at 3k RPM in 2nd gear or even first gear. I never actually do this and just shift at about 2.5k but was wondering as to whether there is a difference in cruising at 3k in 2nd vs 5th.

 

It just used more gas if you're in a lower gear than you need to be. The car can certainly be driven at 3K rpm... but why would you cruise in second?
Go into the highest gear you can while cruising. Now if you're in trafic or something, then it's normal to just keep it in 2nd most of the time until things start to move faster.

 

Youll just use more gas. Usually if Im cruising at 40 to 50 Ill try and use 5th but usually I stay in 4th at 2000rpms. The rule of thumb is stay about 1500 rpms and youll be set

-matt