sundevil

Is this okay? Is it going to hurt my mpg or engine in flat Arizona? 75 is at 3000 rpm.

jchappies

Auto or manual?

The sweet spot for an auto seems to be around 22-2400RPM

sundevil

It's a manual

Biginboca

I don't think it will hurt your engine. I cruise hours on end at 3100 on road trips not a problem. The 3.8 does better at higher rpm it makes better power. I have noticed that sometimes I'll get better mileage in 5th gear at a higher RPM than in 6th gear on the same route. The only way to know about the mileage would be to actually compare it before and after, but definitely a higher rpm doesn't always equal worse mileage in these non aerodynamic bricks we drive.

Wandell

Yep, it's all about being in the "sweet spot" between lugging the engine and revving it too high.

kevinlee

Been driving 170 miles down the interstate at about the same rpms every other sunday for over two years. Hasn't damaged anything yet. About the mpgs I get about the same on the highway as in town (14ish) but I think it has more to do with the 35" tires than the rpms. I don't use 6th gear much because it is fairly hilly and hard to maintain speed going up hill in 6th.

Mike H.

2800-3200rpm never hurt the 4.0 in my XJ, and has not hurt the 3.6 in my JK...
as for mpg's, I find they are affected more by mph (aerodynamics) than rpm.
I find anything over 70mph kills mpgs... regardless of rpms... and 65mph is even better.
I know our (I'm in PHX) speed limits outside of town are 75mph, but I have found running along at 70mph I am not the slowest vehicle on the road.

Trail Jeeps

The 3.8 loves RPMs. Seems like they do just find wound up for long periods of time. 3.8's don't like heat and they don't like load, which is why they were so perfect for a Jeep. They guzzle raw fuel when they get hot to keep themselves cool, one of the reason why fuel economy in the 3.8 sucks so badly, so keeping the RPMs up on the fwy keeps them from working too hard and seems to offset any additional fuel being burned by the high RPMs.