# best speed for highway cruise vs best mpg



## boucivicsir (Aug 17, 2021)

got a new to me Cruise 2017 TD 9 speed. I did a few tests and whatnot for me ideal speed is around 70mph (112 km/h (im in Canada)).
mpg is impressive and it's not slow.
somebody else can relate for a 'best speed vs mpg'?


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## 6speedTi (May 18, 2018)

My 2018 sedan manual gets its best according to the computer between 70 to 75 mph. There are several factors though. Air-conditioning setting, humidity and temperature, tire conditions and alignment. To mention a few and how many passengers or driving solo. My computer can maintain a window between 52 to 58 mph average.


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## boucivicsir (Aug 17, 2021)

and do you calculate at the pump? is there a difference? i mean does the computer reads high or low ?


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## Johnny B (Jun 4, 2019)

I found this question interesting. The theory is a diesel engine is most efficient at max torque RPM, which is 2000 RPM.
According to GM it starts to archive good torque starting at about 1750 RPM.
All that said, I would start by putting it in the highest gear at 1800 - 2000 RPM and you should be golden. Maybe 

And FWIW, I track my MPG and compare it to the DIC. The DIC MPG (for my car) reads 3.5% high.









2014 Chevrolet Cruze Clean Turbo Diesel


The Chevrolet Cruze Clean Turbo Diesel, or Cruze 2.0TD as it will be called, expands the popular Cruze lineup with an efficient yet spirited diesel engine. The vehicle is essentially the diesel-powered Cruze sold in[...]




gmauthority.com


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## 6speedTi (May 18, 2018)

There is an algorithm that is factory set on the computer. I had a 1997 BMW and the computer was always reading higher than actual. Finally one day I came across some information on how to make adjustments up or down. So I recalibrate my BMW computer using the given procedure. I finally got it within 1/10th of a MPG but only for highway driving. When you mix it up the calculations are not accurate. I did mostly highway with the BMW so I was happy with the computer calculations after I adjusted it. So to answer your question I did one long highway run on my Cruze. Here is what I did. I topped off at a service station. Then did a highway trip just over 300 miles. On the way back I stopped at the same service station and used the same pump and topped it off the same way. The computer read 53 MPG Average. My actual calculations using the fuel pump and miles driven was a surprising 58 MPG. So each vehicles computer might be preset within a certain tolerance that GM considers normal. I'm guessing here based on what I experienced from my BMW. Way too many factors involved for accurate numbers but you should be close. I can safely say if I drive strictly highway between 70 to 75 mph with the AC on by myself the computer will calculate just over 735 miles to empty. I recommend do the top off method and go drive. Then top off again and compare your figures. 
That's my long story short. 😂


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## oregon_rider (Jul 21, 2017)

70 mpg hyper-miling by car and driver...









The Prince of Parsimony: Squeezing 70 MPG from a Chevy Cruze Diesel


At a steady 55 mph, no air conditioning, with minimal brake or throttle inputs, a 2017 Cruze Diesel crushes the 900-mile range mark in California. Read the story and see photos at Car and Driver.




www.caranddriver.com





jeff


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## Cruz15 (Mar 17, 2016)

Strictly rpm to rpm I get better overall in 8th gear not 9th gear. I weigh close 300 lbs so Im taxing the engine a bit. I find as well there are certain speeds that if I go 2 - 4 kph over or under the mileage is lower.
This car is much harder to get the max mileage for me than my 2015 was. Mileage I find is not even close to linear curve.


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## Barry Allen (Apr 18, 2018)

Johnny B said:


> The theory is a diesel engine is most efficient at max torque RPM, which is 2000 RPM.
> According to GM it starts to archive good torque starting at about 1750 RPM.


The LH7 engine has a flat torque curve from 2,000 rpm to a little past 3,000 rpm. GM states "90 percent of [torque] is available from 1,500 to 3,250 rpm."

The torque from this engine is electronically limited because of the M32 manual gearbox (320 newton-meters = 236 pound-feet). The engine caps the torque to make a flat torque curve, so we really don't know the actual torque peak of the engine.

Since 90% is available from 1,500 to 3,250 rpm, best efficiency is within that band of engine operating speed.


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## boucivicsir (Aug 17, 2021)

right now i'm getting 47 us mpg. It's my fisrt real tank / week with the car. I'm pretty pleased. I had a 2011 prius which was around that, so have the cruze TD is a huge plus for me / our familly. I'll stick to 70 mph (112/114 kph) and it' sfine. I asked the question because some other car avec a very specific rpm range that it's like hot or miss. 
For the small time I've own the car it seems that from 45 to 70 mpf, the consumption looks to be the same so the faster, the better up tp 75 mph. (sorry english is not my first language, so explaining that is not super easy)...

other question / thread derailment; any of you installed a boost gauge / logged boost ? IM've read documents and such but 'm wondering what could be the boost at cruise speed...
also interested by EGT just to know.


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## BodhiBenz1987 (Jan 13, 2018)

I find my car's "sweet spot" for mpg is somewhere in the 60-70 mph range, but even going up to 80 it doesn't go down that much, like it does on some cars. Under 60 it can do really well but can be harder to maintain momentum. I find the computer estimate is usually relatively close even though it always differs a bit from my hand calculation ... it seems like it always reads a touch high if I've been doing some stop and go, and reads a bit low if I've been doing tons of highway. If you want to track by hand, a Fuelly account is an easy and fun way to track your results. Here is mine for the Cruze: Algie (Chevrolet Cruze) | Fuelly
For a gauge, I use a ScanGauge II, which can tell you several parameters including boost and all three EGTs. It will also tell you about the car's regen status which is a nice help because it's ideal to make sure the car can finish a regen when it starts one, by getting it out on a highway until it's done. You can also get a Bluetooth ODBII unit and use a phone app like Gretio or TorquePro if you prefer to use the phone. I like the SGII because it is small and self-contained.


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## pandrad61 (Jul 8, 2015)

When I did my record run on my banner I did it at 60-55mph. This is my gen 1 sweet spot of speed to MPG ratio.


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