Accepted cruising RPM?

[AndyL]

With 4.10s and 33" inch tires my engine is spinning pretty good at 75. What is the accepted RPM range for extended intervals?

[gmctd]

You must be talking about the '86.

4.10's, 0.73od, 31" I get around 2200 at 70mph.
Direct is around 3000, iirc.

I never did like it revving that high, but I've read a number of posts attesting to 20mpg, and more, at those mph\rpms.

Drove mine a year that way, got 15.5mpg.
Added overdrive, mileage dropped to 14mpg, and I never shift out of od.

Go figure....

[AndyL]

This is actually on the '99, I sold the '86 and need to update my profile. With an engine that red-lines at 3500 RPM it just seemes high if I were to cruise at 2500 RPMs for 12 hours going to Florida.

What do you think?

[Dieselboy]

IMO, you should be at the "end" of the torque curve at your top highway speed. For me that's 75 mph; for Dr. Lee that's typically 80. The idea is to be in the middle of the curve when slowed down on a hill ~65.

Our 96 suburban turns 2400 @ 75, while my truck does 2050. I have plans to regear my 85 in hopes of getting the same kind of highway performance the 96 has.

I wouldn't blink an eye at a good running 6.2/6.5 turning 2500 for long periods. The 6.2L forum had a good thread on sustaining high rpms for long durations. (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002181)

[tswartos]

Depends on how u want to balance the trip...time, mpg, comfort/noise.

Best mpg - 1800 RPM...best power - 2050 to 2300 RPM...best time - whatever your comfortable with smile.gif

[Marty Lau]

Originally posted by tswartos:
Depends on how u want to balance the trip...time, mpg, comfort/noise.

Best mpg - 1800 RPM...best power - 2050 to 2300 RPM...best time - whatever your comfortable with smile.gif smile.gif Tim, well stated! :cool:

[patrick m.]

my truck really likes 2500 rpm :D , so thats where i keep it (most of the time) unless i have to jump around someone ;) that rpm = 75mph

[Reid]

I've got a 1995 2500 4x4 6.5 bought it used with 120,000 miles and installed the max e tork chip and turbo master. i've been commuting 120 miles a day at 78 m.p.h @2700 r.p.m. getting 18-19 m.p.g. in 145,000 miles since i started driving this every day; one injector pump and one fsd has gone bad. relocated the new fsd onto the skidplate with heat sink. 265,000 miles now. it won't stop!

[moondoggie]

Good Day!

WAAAAAY back when I became a member, I read that the 6.5 liked three rpm's:
</font> 1800 for max mpg, unloaded;</font> 2200 pulling a load on the highway;</font> 2800 pulling a load in the hills.</font>I have NO idea if these are right or not, or where on the Page I read them. My trucks do seem to like these rpm's, however.

For me, best mpg seems to be at lowest rpm, within reasonable limits. With my Gear Vendors Aux. OD, I'm only turning ~ 1600 at 55 mph, & I get LOTS better mpg at 55 than at 70 mph.

Blessings!

Brian Johnson, #5044