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Tach Readings With Duramax

sydscrew

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sydscrew Enthusiast

sydscrew

Posted
Posted

I just took delivery of my 2009 Sierra Crew Cab SLT 2500HD 4x4 with the Duramax engine, and I am wondering what the normal tach reading is for highway travel with the cruise on and/or off at 60 mph or 100 km/h. The trip I had yesterday at a speed of 60 mph or 100 km/h for 210 miles when on cruise the tach stayed at 1500 rpm. I kept the truck in 2wd the entire time and it was empty (no load). I am looking for the sweet spot (tach rpm) where the engine will give the best feul economy at highway speeds.

 

As an example, my old Ford F150 at 60 mph the tach would be just about 1650 - 1700 rpm and I was told that if I could keep the revs down below 1800 rpm, that my mileage would be good. Going over 1800 fpm and the mileage would drop dramatically while driving.

 

Thank you

pwall Senior Enthusiast

pwall

Posted
Posted

That's about what I see.

Took a trip last year to Newfoundland (home) and put on over 10,000kms. Kept the truck at 60-65mph, which seemed the best over-all fuel economy.

Shaners Senior Enthusiast

Shaners

Posted
Posted

55-65 mph wil give you your best milage. Anything over that really causes it to drop. These trucks are anything BUT aerodynamic!

masterp2 Enthusiast

masterp2

Posted
Posted

1800-1900 rpm empty on the 5 speed

1700 rpm on the 6 speed

 

you may find that 70 gets the same mpg as 60 with your gearing.

jpringle3 Enthusiast

jpringle3

Posted
Posted

I also found that I get better mileage with it closer to 70 than 60. living in the mountains, I have found that using the cruise control in hilly areas costs you also. On the interstate I will use cruise, other than that no. With a six speed the RPM is just about 1500 at 100k

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