Disappointing Gas Mileage

[DennisV]

OK we are back from vacation and I did calculations based on filling the tank when it is half full (I'm paranoid ). I averaged 16-17 MPG, all highway from Las Vegas, Nevada to Arlington, Texas.

 

Mikey

 

How fast did you drive on those freeways ?

[MikeyNV]

DennisV:

65-75 with some pretty good climbs in the Arizona area (I-40). I should have mentioned that I was packed with luggage and 6 people.

[Backfire1]

Wow,

I don't get it.  16 - 17 MPG is great.  Maybe it is the stop and go driving around town that is the cause of the poor MPG.  I have not done any road trips.  I will continue to monitor my MPG and I will try to drive with less zest. 

[wollip]

Axulsuv / Glenn -

 

Thanks for your post yesterday. You gave some really good tips for improving mpg and helped me add items to my list of "just too many variables".

Edited July 21, 2014 by wollip

[Bates]

I just bought a 3500 SV passenger, V6 engine 2012 version for our pre-owned lot. Been used by a framing crew, god knows how they drove it (it's in below average shape)

 

Flipping to the fuel economy measure shows 14.6L/100km or 16.11mpg. No idea when it was last reset, showing 37,000km on it.

[axulsuv]

Backfire1 ;

No Worries , I feel your pain ...

I try to fill up at about a 1/4 tank , to keep my fuel pump cool and give it a long life :) It usually takes 20 to 23 gallons to top off my tank when I fill up and I've gone around 425 to 450 miles . on one trip I did see see 552 , but I had driven a scary distance with the low fuel warning glaring at me ... I don't trust gas gauges .....!

Get your Dealer or a good alignment shop to check out your alignment , it is crucial to these heavy weights , And remember , your driving around a 6000 pound + box , Learn to let inertia be your friend .

Have a great day  :)

Glenn 

[Backfire1]

I received my OBD II Bluetooth scan tool.  It shows no problem with any of the vans sensors.  I am going to use it to help teach me to drive more efficient.  I was hopping I had a bad sensor and that was the problem.  When I go to the dealer for my next oil change I will speak with the service tech.  Also I am going approximately 300 to 320 miles per tank, a tank being 22 to 23 gallons at fill up.  When I fill up my van tells me I have 345 mile to empty.  When I first got my van it said 450 miles to fill up, but as I have used it that number has gone down.

On another note my last truck a 3500 service body went 250 miles on 26 to 27 gallons of gas.  Now that is painful.

Maybe I need to reset my computer.  Does anybody know how to do that?  Do you think it would help?

[axulsuv]

You can disconnect both battery Terminals from the battery and touch the 2 cables together (away from bat. ) For about ten seconds and that will discharge all the capacitors in the control units , The only thing that should not start from scratch is the odometer , All the other inputs and outputs will have to be relearned . (BMW calls this a battery dump in their tech language ...)

Glenn

[Hawkeye77]

Backfire1, Glad to hear that you got the OBD II reader. I

bought another one for my car, that way I can leave the other in my NVP. Have you checked your air filter to see how it looks? When I installed the CAI, I noticed that the factory air filter smelled like oil. Just a thought.

[Mc2guy]

Your fuel economy is a product of three things: the engines brake mean efficiency at various loads (a constant), the amount of mass accelerated (how heavy is the van and how OFTEN is it accelerating from a stop), and the aerodynamic drag of the vehicle combined with the velocity at which you drive.

 

Assuming all V6 engines will be within 5% of each other in efficiency, lets rule that out as a cause.

 

You mentioned a "route" and that you drive mostly stop and go between locations (lots of light and slowing down for traffic counts).  This contributes to accelerating your mass.  The more often, the lower your mileage.  

 

This leaves the aerodynamic drag and velocity at which you drive.  Drag is defined as the Frontal Area of the Vehicle (A) times the density of air ® times the coefficient of drag (Cd) times the velocity of your vehicle squared.  A(Cd)RV^2.  

 

We can't control the air density, but we can control the other variables.  Adding a roof rack with ladders penalizes you TWICE.  First it increases the frontal area of the vehicle by making it look bigger (taller), so A increases.  Second, it increases the coefficient of drag because racks and ladders do not present a smooth surface for the air to travel over.  Lastly, speed kills when it comes to fuel efficiency.  I mentioned drag increases with speed, but it doesn't just increase proportionally like with the size of the vehicle; it increases exponentially, so if you double speed from 40 to 80 MPH, you are actually quadrupling the energy required to go that speed.

 

In conclusion.  Driving with a ladder rack, making multiple stops, and traveling at highway (65mph) speeds between lights will kill your mileage.  End Stop.  Just physics.

[radin2son]

Great explanation. Thanks.

 

Is there any difference in drag and fuel efficiency between the frontal area designs of Nissan vs the Sprinter/Transit? (Rhetorical question) Somebody must consider this in the design process, but we only know mpg of each design through word of mouth since mpg isn't on the window sticker.

 

rad

[DennisV]

Every vehicle has a measured "coefficient of drag" usually expressed as a number in the 0.30 to 0.50 range with some higher and lower.

 

I remember hearing the Promaster was in the 0.35 range which was better than the Ram pickups. But with the much greater frontal area, the v6 Promaster will not equal the v6 in a Ram 1500 pickup by a long shot. I don't know what the cd numbers for the NV vs the Sprinter are, but I imagine the Sprinter is a tad bit lower than the NV due to the NV's hood. I don't know the frontal area difference either but for comparison sake, let's assume they are the same.

 

That said, if the drive trains were exactly the same in both, the Sprinter might probably be marginally more fuel efficient if both were driven exactly the same speed. But due to exponential increase in drag as velocity increases, that margin would would quickly disappear if the Sprinter was driven just a couple of mph faster than the NV. Either van, driven at 65 would burn less fuel than the other driven at 70.

 

Speed kills mpg in these big vans no matter who makes them. Same with hard acceleration.

 

The biggest factor by far in mpg variance is driver habits.

 

Very good post there Mc2guy. I've seen your posts on the other jumbo van forums. Are you considering an NV?

[Mc2guy]

Every vehicle has a measured "coefficient of drag" usually expressed as a number in the 0.30 to 0.50 range with some higher and lower.

 

I remember hearing the Promaster was in the 0.35 range which was better than the Ram pickups. But with the much greater frontal area, the v6 Promaster will not equal the v6 in a Ram 1500 pickup by a long shot. I don't know what the cd numbers for the NV vs the Sprinter are, but I imagine the Sprinter is a tad bit lower than the NV due to the NV's hood. I don't know the frontal area difference either but for comparison sake, let's assume they are the same.

 

That said, if the drive trains were exactly the same in both, the Sprinter might probably be marginally more fuel efficient if both were driven exactly the same speed. But due to exponential increase in drag as velocity increases, that margin would would quickly disappear if the Sprinter was driven just a couple of mph faster than the NV. Either van, driven at 65 would burn less fuel than the other driven at 70.

 

Speed kills mpg in these big vans no matter who makes them. Same with hard acceleration.

 

The biggest factor by far in mpg variance is driver habits.

 

Very good post there Mc2guy. I've seen your posts on the other jumbo van forums. Are you considering an NV?

I don't have a Cd for the NV, but Im guessing it's around .40 or so. The long hood actually shouldn't effect it too bad, it's the square back that kills vans aerodynamically. A tapered finish (think teardrop) makes a bigger difference than a smooth snout.

 

Yes, I am considering both the NV and the Transit. Ford has made some poor design decisions that are pushing me toward the NV, but I'm definitely a Ford guy at heart. The NV's gas mileage is a turn off, but I'm figuring 13.5 with the NV vs maybe 15 with the transit ecoboost, so not a huge deal given my annual mileage of around15,000.

 

The big issue for me with the Transit is the low tow rating and non configurable seats in the wagon. Kind of a deal killer.

[radin2son]

Mc2guy.

 

Why so low on the NV mpg estimate? You should be able to get about the same as the Transit.

 

Does breaking up the air via a spoiler or box/rack on the back make any difference/improvment in aerodynamics? I have seen semi trucks with a foldable "wedge" device on the rear doors to achieve the tear drop effect you mention.

[Mc2guy]

Mc2guy.

 

Why so low on the NV mpg estimate? You should be able to get about the same as the Transit.

 

Does breaking up the air via a spoiler or box/rack on the back make any difference/improvment in aerodynamics? I have seen semi trucks with a foldable "wedge" device on the rear doors to achieve the tear drop effect you mention.

I'm basing my estimate on the anecdotal information I've seen posted on this site combined with posted data from various industry reviews (trucktrend, edmunds, etc), and Fuelly.com.  All of these point to an average of somewhere less than 14mpg in combined driving for the NV.  

 

The transit is a direct injection turbo V6 vs. a multipoint fuel injected V8 in the Nissan.  Essentially, the ecoboost it is the next generation of gasoline engines.  It is more efficient thermodynamically because the direct injection allows for more precise control of fuel/air ratios and the turbocharging means it can function as a small displacement V6 when lightly loaded.  It can suck gas with the best of them if you lead foot it, but the ecoboost V6 is a more efficient motor given a careful driver.  The Transit is also about 1500 lbs lighter because it is a modified unit-body vehicle, whereas the NV is a full body on frame, which is also why it has higher payload and towing ratings than the Ford.

 

Yes, creating a more laminar air flow off the back of a vehicle can significantly improve drag, hence those devices on semi's.  Here is some neat info on Cummin's project truck http://www.cummins.com/cmi/navigationAction.do?nodeId=252&siteId=1&nodeName=SuperTruck+Gets+Close+Inspection&menuId=1050

[radin2son]

I like the turbo and small displacement engine on my TDI but I'm not sure I would go this direction with a cargo van. I would prefer a diesel if mpg was an issue for city use.

 

Interesting super truck on the cummins link you provided.

[axulsuv]

I'm back again , Now after about 600 miles on my new daily commute , my mileage has settled in at 19.2 on the average meter ... I put it down to a shorter commute with more time @ stoplights and summer blend fuel . And as to the fuel efficient semi's , I know if I'm drafting one with the lower side skirts etc. on a long trip , the frontal load on the van is much less while not being any where near as close to them as a standard old fashioned rig .

 And I'm a old Ford lover too , but look at the build quality of the nv closely , before you jump on a transit ... A real frame is worth alot in the long haul ...

 Glenn 

[Backfire1]

Just wanted to give an update.  My fuel mileage is still sub par compared to what I thought it was going to be.  Never getting below 12 but never getting over 13.  I guess it is what it is.  I do love the van and I am glad I purchased it.  I think it boils down to the city driving and ladder racks plus I keep the shelves full of tools and supplies.  I used to drive a truck that would get 10 MPG so the NV is an improvement.

 

On a side note I did have the check engine light come on.  I checked it with my OBD reader and it said the code was a transmission communication issue.  I reset it and it has not came back on.  When I go to the dealer I will let them know.

Edited August 30, 2014 by Backfire1

[axulsuv]

Did a Trials event in Thurmond NC last Sunday , Filled NV with ethanol free 93 , riding gear , Triton aluminum trailer with 2 bikes and 3 people in van . Reset mpg average at start of drive . 584 miles later back at home Sunday eve. , Display reads 25.1 average ...:) Has dropped to 21.9 after my weeks commute . I love this big ole' box ...!

 Glenn ,  it's all in how you drive , or mine is a freak ....

[Glidedon]

I've got the NV2500 high roof v6.  I installed a bluetooth OBDll reader ( $28 Amazon)  and Torque on my Android phone.

 

The computer on board was very optimistic compared to my pencil and paper calculations. Fortunately there is a trim adjustment in the software ( on the Torque app)  Now the read out is accurate.

 

I'm getting 14.5 in the city and between 17 and 19.5 on highway very dependent on wind direction and under 65 mph, double checked with pencil and paper.

 

The Torque app also displays real time mpg. This will show you real quick what sucks down the gas and is good for adjusting your driving habits

 

I also read some where that the high roof had a lower coefficient of drag than the low roof model. 

[Backfire1]

Just wanted to update those who have interest.  Still averaging 12.4 MPG according to fuely app.  The best I have ever had is 13.2 MPG.  I have right at 10,000 miles.  Still waiting for those 15 plus mpg numbers to start rolling in but does not seem to be happening.  Van is great have had no problems.  I will update again at 15,000.

[Hawkeye77]

I am still following along. Hate to see the low MPG's. I am out of the country for a while, so I am not sure how the NVP is doing with fuel economy. My wife usually doesn't monitor it like I do, but she has six kids to ferry around till I get back. I will be data logging and looking for ways to improve MPG's when I return. Good luck.

 

Donald

[Daydreamin520]

This was a really good thread to read all the way thru'!  As a future 2500 V6 HiRoof owner, I was glued to each posters story of mpg lows and highs.  Like a great TV series, I couldn't wait to see what was in the next "episode".  Lol.  In Tucson, with mostly stop and go street driving, I don't expect to have the best numbers but, since I do drive like a lil' old lady, I think it will be more than satisfactory for the weekend trips I have planned.  Thanks all, for your invaluable input.

[axulsuv]

Just wanted to update those who have interest.  Still averaging 12.4 MPG according to fuely app.  The best I have ever had is 13.2 MPG.  I have right at 10,000 miles.  Still waiting for those 15 plus mpg numbers to start rolling in but does not seem to be happening.  Van is great have had no problems.  I will update again at 15,000.

It's just got to be the ladder racks .....

[RICK]

I can relate to the mileage with my 3500 sprinter I just retired with 38,000 miles. My van weighs in around 9200# daily. In the 6 years I have personally owned and driven since new my average mph in 6 years is 12.5 mph at an average of 12 mpg. I do 75% or more city driving in Los Angeles. Stop and go. Also in the building trades and make approximately 5 stops a day. On the highway it will get 19 mpg, but the LA traffic and slow average mph is a killer along with the weight.

 

Will see how my 1 day old 3500 high top sv pans out. It's totally empty, but in a few weeks will be up to crusing weeight when the shelving and material gets installed. So I might be able to compare empty with full weight and also get a weight on it too.

 

Now off to lowes to buy some masonite to finish the top half side panels.

 

Rick.