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6.2L RPM Sweet Spot

PGW

PGW

1/2 ton status
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Apr 19, 2007
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CC, TX
Hey guys, I've done a few searches trying to find this out but did not find what I was looking for. About what RPM would a 6.2 get the best efficiency at highway speeds? I looked at some power graphs and it seems that max torque comes in around 2,000 RPM. Thanks. :D
 
Peak efficiency is about 1800 rpm at 65 mph. My 83 C10 pick-up spins at 1834 rpm at 65 mph and on the freeway gets 25+ mpg. For comparison my 81 K5 with 6.2 used to spin at 2550 rpm at 65 mph and got 16.5 mpg on the freeway. That's roughly 1.2 mpg lost for every 100 rpm increase at 65 mph...of course aerodynamics and weight as well as rolling resistance all contribute. If I just drove the C-10 in drive instead of OD (2600 rpm at 65) I'd likely see mileage drop to 19 or so.

I think the dieselpage.com has a chart showing brake specific fuel comsumption for the various rpms for the 6.2. They also claim 1800 is the sweet spot.

Rene
 
1800, 1850, is considered the sweet spot. Pick out what speed you want to travel on the highway at and set your gearing / tire size to run at 1800 rpm at that speed.;)
 
My friend and I are both planning to change tire sizes and re-gear our 6.2L trucks. I see here that some members are recommending 1800 RPM cruise speed as a target but this conflicts with the data posted here:
http://coloradok5.com/forums/showthread.php?t=173710

The data in the linked charts seem to indicate that maximum torque and minimum fuel consumption occur at around 2200 RPM, not 1800. Can someone please explain this discrepency?

Thanks,
Mike
 
That is lbs of fuel/hp/hour.

It's a good chart to see, but the real world experience say 1800 rpm is the fuel economy sweet spot.

Real world...

81 jimmy, cruise rpm was 2600 rpm. Freeway mileage was 16.5 mpg. OK, it was lifted, and running on 39.5's. Factor that in and I doubt it would have seen better than 18.5 mpg at that rpm (no lift and radials).

83 1/2 ton I also have. Cruise rpm is 1840 rpm. Freeway mileage is 24.5 on a bad day and slightly over 25 mpg normally. It is 2WD and not lifted though.

From 1800 rpm upwards you'll lose about 1 mpg for every 100 rpm increase in cruise rpm. This assumes cruise speed is roughly 65 mph.

There are other variables of course, but this is a pretty good rough idea of what to expect.

rene
 
sloth said:
My friend and I are both planning to change tire sizes and re-gear our 6.2L trucks. I see here that some members are recommending 1800 RPM cruise speed as a target but this conflicts with the data posted here:
http://coloradok5.com/forums/showthread.php?t=173710

The data in the linked charts seem to indicate that maximum torque and minimum fuel consumption occur at around 2200 RPM, not 1800. Can someone please explain this discrepency?

Thanks,
Mike
Click to expand...

Actually it's blurry but it still shows 2000 RPM as peak torque on both the C code and J code engines.
I think 1800 to 2200 will be close in mileage numbers though
 
imiceman44 said:
Actually it's blurry but it still shows 2000 RPM as peak torque on both the C code and J code engines.
I think 1800 to 2200 will be close in mileage numbers though
Click to expand...

Rene is saying 1800RPM is max MPG. You on the other hand are saying 2200 is peak torque. I cannot see how peak tourque could be the same RPM as minimal feul consumption RPM. I could be wrong. I would say in my driveing experiance with a few 6.2's, while only one had a tach, 1984 gmc jimmy with th400 ran at 65 around 2300 RPM stock gears???? and 31" tires. after I lifted it 4" with 35" tires, 3/4t xles with 4.11 gears, and swaped in a 465, it was running about 1900 RPM. And after the swap I got WAY better MPG. Granted, I do belive that the th400 was slipping pretty bad at highway speeds, hence the trans swap. The speedo was certainly off a little, with gear change and 35's, and the tach could have been off too.:dunno:

Balzer
 
Rene and IceMan-

Thanks for the quick replies! I agree that the charts are blurry/have fat lines. I was a little suspicious that 2000 RPM was actually the max torque value since it was the number cited in the upper right corner of the chart. I also agree that all of the charts in the existence do not make up for real world experience; I just wanted to make sure that real world experience was what I was getting (as opposed to the often encountered internet repeaters that just spew numbers that they "heard from their brother's friend's uncle...")


Balzer-

I understand your concern but, as you can see from the charts, minimum specific fuel consumption does occur closely to the same RPM as maximum torque. This would seem to me to be ideal from an engine design standpoint. In a perfect world, an engine designer would want the best efficiency point of an engine to be as close to your maximum output as possible.

Thanks to all of you for your real world input!

-Mike

EDIT - I should add that drag due to air resistance increases roughly at the square of the speed so, a lifted truck vs. a stock height truck would definitely show different values for fuel consumption due to the greatly increased frontal area. There's also the increased rolling resistance of larger tires...
 
Last edited:
diggin up this old thread.

how drivable is a 6.2 nv4500 with 4.10 and 37s? that puts the 70mph at 1955 rpm. Will the 6.2 have enough juice to get going in 2nd gear or will it lurch forward like its undergeared? i have 4.56 and 410 options immediately available. Wondering if its as good as it looks on paper.

Thanks
 
4.10's and 37's it'll be fine getting going in 2nd gear.
 
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