TACHOMETER Shift Ranges - Achieve maximum fuel economy

[BKneeland]

Where do I go to find the optimum (recommended) rpm shift points on the tachometer for a 2004. 5, 6 spd manual, 3. 73? rear-end, 315 tires, 4x4, SWB diesel pick-up... ... ... ... .....

 

[Motorhead]

If you can stay below 2K rpm then that is the most economical range. I also have a 6 speed truck and I try to shift at 2K. The optimal torque range on the 325 engine is 1800 rpm.

 

[HBarlow]

Peak torque is produced on all 24 valve and HPCR ISB5. 9s from 1500 or 1600(depending on engine family) to 2700 rpm. Keeping rpm down low like below 2000 rpm as suggested above will produce the greatest economy.

I found a Cummins website and posted it a year ago that said the most efficient highway cruise rpm for the late model HPCR engines was 1950 rpm. I can't find the site now.

 

[BKneeland]

Thanks for the info. With 315 tires (and reset speedometer for larger tires) my highway best mileage seems to be at 1890 to 1900 rpms at 70 mph.
I remember driving a 4 wheeler that had OEM "tick marks" on the vehicles tach indicating the recommended shift rpm points.
WEB site "Midnight Trucking Radio Network" (Midnight Trucking Radio Network) shows a decal for CAT, Kenworth, International and Peterbilt that you stick on the tach for ideal shift points-Cool Idea.

 

[Buffalo]

I attended a couple of seminars given by Mr. Dennis Hurst (the head man at the Cummins Engine Plant that produces our engines). He told us that the engine was designed & built to work most efficiently in the 1800-1900 rpm range. These seminars were at May Madness where you can get some very good information.



During last years vacation (towing my 25', 7000+ lb. trailer) I had to drive at about 55-57 mph for an extended period of time on Hwy. 99 from Bakersfield to Sacramento, CA. On one fill-up, I got 16. 9 mpg, another at 16. 2 mpg & two in the high 15 mpg's. My WORST fill-up was a bit over 10 mpg's. Normally, my truck gets around 17 mpg's, around town, not towing.



I couldn't believe the great mileage on Hwy. 99. However, that area is as flat as a pool table, no side or head winds, in line with thousands of 18 wheelers & driving slowly gives one great mileage. I don't remember the rpm's at that speed.



Joe F.

 

[Schrowang]

Whether running bobtail or towing my 5'er, I keep the rpm just below 2,000 in 6th. With my 6-speed and 4. 10 diffy that translates to 60 mph on the Interstate and that gives me the best mileage. Of course on steeper hills I have to downshift to 5th when towing.



Rowing up through the gears from 1st I try not to exceed 2,000 rpm and not let the revs fall below 1,500 before completing the shift to the next gear.

 

[MickeyMiller]

I also find around 1900 rpm is a sweet spot for my '03. For best milage, I watch exhaust temp and try to keep it below 600*. That means downshifting on hills and running 2300-2500 rpm up hill in 5th (I try not to load 6th gear anyway) to keep the exhaust temp down.