CDI low roof highway mpg, what is reality?

I'm looking for a 144" van for a camper and wondering what realistic highway mpg is for a low roof, 65-70mph, I realize speed will reduce it and I'm not worried about short trip mpg as a difference between 15 and 18 won't amount to much over 60 miles, but 21 to 26 makes a big difference over a few thousand miles.

I have a credit with GDE as well, so if you have that tune I'd like to hear the realistic improvement as well.

*CDI is pretty much blutec by my standards, even though bluetec is still Common Rail direct Injection
 
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197steve

New member
I had a 2013 144 low roof crew van, and it got about 19.5-20mpg when I would lock in the cruise control at 75mph. I now have a 2016 144 low roof crew van and it is running about the same as the older one did.
 

asimba2

ourkaravan.com
If you're really interested in fuel economy, you may want to set your sights on a 4 cylinder, made only in 2014, 2015 and 2016. The V6s seem to have trouble routinely getting over 20 MPG, where a 4 cyl will be mid-20s and often higher.

My 2016 4 cyl high roof averages 24-27 MPG. The lowest tank I've ever recorded was 21.8 MPG.
 

dante

Member
Driving around 75mph from MA-FL-MA (distance was 3000miles) this past April - I barely managed 18mpg. I have a 2012 V6 lowroof 144 passenger van.
 
An in line engine would be my strong preference and I haven't totally ruled out the t1n, although I would prefer the newer van.

Unfortunately I'm looking for something I can pay cash for, pretty much ruling newer vans out.

I have to wonder why the v6 struggles so much with fuel economy, I can easily get 18 mpg from my 2006 dramax with over twice the displacement.
 

4wheeldog

2018 144" Tall Revel
An in line engine would be my strong preference and I haven't totally ruled out the t1n, although I would prefer the newer van.

Unfortunately I'm looking for something I can pay cash for, pretty much ruling newer vans out.

I have to wonder why the v6 struggles so much with fuel economy, I can easily get 18 mpg from my 2006 dramax with over twice the displacement.
Two things are different, 4 cylinder vs. V6. The V6 is less highly tuned, and suffers from being backed by an ancient 5 speed tranny.
The 4 cylinder is more highly tuned, and benefits from a more modern 7 speed transmission.
 

Midwestdrifter

Engineer In Residence
Your duramax isn't pushing a 8ft tall brick around either... And it probably doesn't have a DPF to regen.

The 4 cylinder has only two camshafts (instead of 4) it has a very specifically tuned (for efficiency) powerband, which the 7 speed lets is stay inside of. The 7 speed also has a more efficient torque converter design and/or program which helps. The 4 cylidner has a lot less timing chain as well.

As a general rule, the higher the output per displacement, the higher the efficiency. The higher the combustion temps, the higher the efficiency.

The 4 cylinder also has better designed main and conrod bearings, which tighter clearances. This means less oil needed, lower pumping losses, and lower drag on the bearings.
 
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Your duramax isn't pushing a 8ft tall brick around either... And it probably doesn't have a DPF to regen.
Do the CDIs have a regen? I thought it was just blutec.

I wonder how well a diffuser at the top rear would work for reducing the vacuum that holds the van back, the front looks aerodynamic enough for 65 mph.

I've also noticed relatively high higway rpm, I'm sure the 7 speed would help with a broader range of gears.
 
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autostaretx

Erratic Member
Do the CDIs have a regen? I thought it was just blutec.
Both BluTec and DPFs, but it's model-year dependent (i forget which came first).
I wonder how well a diffuser at the top rear would work for reducing the vacuum that holds the van back, the front looks aerodynamic enough for 65 mph.
There have been a couple of threads about "AirTabs" ... use the Search...

--dick (25 mpg+ on highways)
 
2007+ NCV3s have a DPF and therefore a regen cycle. Bluetech wasn't introduced until the 2010 MY, IIRC.
Thanks, I found my 05 e320 had a catalitic converter I believe just after the turbo, too many changes those years. I'd plan to have a proper update from GDE so I can use biofuels.
 
--dick (25 mpg+ on highways)
Any tips or tricks? Slow speed?

I read somewhere a few had luck with taller tires, drops the hoghway rpm some. I could see this being more effective in a smaller van.

The only additions I would slap on the outside are a roof fan and an awning.
 

autostaretx

Erratic Member
Any tips or tricks? Slow speed?
Not excessive speed, just drive at legal limit, usually under cruise control.
(downshifting sometimes done if ScanGauge shows greater than 70% load)

...oh, and as my avatar picture and signature block shows:
i drive a 2005 T1N (with the original 15 inch wheels), not an NCV3.

--dick
 
Thanks Dick, it may be my settings but avitar and signature blocks don't show up for me.

I'd buy a t1n in a heartbeat if I could find one that wasn't trashed and at a reasonable price, it seems if the seller prices it right they last 2-3 days on the market, high and they just don't sell.
 
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After pulling my hair out looking I very well may do this, there are just too many crazy fools after the few early ncv3 vans, anything that isn't beat to s' and priced reasonably is sold in a day...



If you're really interested in fuel economy, you may want to set your sights on a 4 cylinder, made only in 2014, 2015 and 2016. The V6s seem to have trouble routinely getting over 20 MPG, where a 4 cyl will be mid-20s and often higher.

My 2016 4 cyl high roof averages 24-27 MPG. The lowest tank I've ever recorded was 21.8 MPG.
 

Legwound

Member
I have a 2010 low roof and drive at 55 miles per hour and can get as high as 23 mpg. I rarely accelerate hard, often coast to a stop or red and generally drive in a very sedate manner. I leave my spirited driving to my mustang.
 

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