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I had a drive yesterday from West Virginia to DC that had very distinct sections of road. I-81 for 30+ miles of wide open, relatively flat interstate at 75-80mph with the cruise on. US50 from Winchester to Marshall VA is country highway with a few stop lights (I mostly hit green lights) and not much traffic to speak of. I was doing about 60-65 on it. I-66 from Marshall to DC is urban interstate, much more traffic, speeds varied from 65 down to 45.
As I hit each section, I reset the MPG average. Obviously these numbers aren't long distance averages, but the MPG gauge was fairly stable, and 30 miles of the same driving style gives a decent view.
You may want to not reset till after you fill your tank, the instant reading that I think you are doing, is not going to be representative of the entire tank.
What are some things I can do to give me just a little more?
1. Put the stock tires back on.
Taller tires do make a taller final gear, but wider tires increase the contact patch, create additional tire to road friction that must be overcome, add more rolling resistance, and increase the forward facing frontal area under the truck.
2. Leave the stock blocks in the rear in place.
Lowering the rear raises the front (your intent, for "leveling"). The tilt back of the truck from the shorter blocks will increase the distance between the lower lip of the front air dam spoiler to the ground. The higher that distance, the more air gets under the truck. The more air under the truck, the more drag and eddy currents created underneath the chassis that reduces fuel economy.
3. If you have 4WD, don't swap front chin spoiler for a shorter 2WD version for "better looks".
For the same reasoning cited under point 2 above, the closer the lower lip of the front spoiler is to the ground, the more air is directed around the truck, rather than underneath it. On your upcoming road trip, take a look at the newest Freightliner Class 8 Semi tractors, with a lower chin spoiler fairing that hovers seemingly only 2 inches from the ground. I couldn't help but notice these tractors on my most recent road trip. With federally mandated electronic data logging in place, these race car like looking semi tractors aren't racing for time... they are competing for fuel economy.
4. Add a sloping rear fiberglass shell / topper
Many aerodynamic studies have shown that managing the slip stream of air at the rear of the vehicle contributes as much to fuel economy as does reducing the drag coefficient at the front of the vehicle. Again, looking at newer Class 8 semi's for physical demonstration of these principles, notice the extra set of barn doors at the end of semi trailers... trapezoidal panels that are deployed enroute to provide a wing like taper on all four sides of the rectangular box... which manages the air slipping past the box, pushing it through like a suppository... rather than the sudden break from a flat back end creating turbulence that costs more fuel. When the rectangular bodied muscle cars of the 1960's (like the Pontiac GTO, Chevy Chevelle, and Ford Mustang) all became "fastbacks" in the 1970's, they were applying the same air management principle at the rear of the vehicle.
You may want to not reset till after you fill your tank, the instant reading that I think you are doing, is not going to be representative of the entire tank.
You can’t drive an entire tank on one type of road, one traffic density, one temperature, one headwind, etc. All you can do, in terms of comparing speeds and driving types, is a snapshot. And that’s all I want anyway. I didn’t buy the truck for its stellar mileage, and the absolute value doesn’t make any difference to me. The point is to find relative gains. I got X mph yesterday, and I changed something, and now I’m getting x+1.
I dont think your truck is getting that mileage. Don't expect that, or you will be forever disappointed chasing those numbers.
That’s what the gauges say. It may not be perfect, but it’s the best data I have. The truck knows its speed, and it knows its fuel flow. It’s not a complicated math problem. And again, the point is relative gains, not absolute values.
How are you getting those mpg numbers? Seems a bit high.
I'm still trying to figure out what my mpg is, one screen will say one thing and barely ever move, the other will show a completely different number but change frequently. Both pics were taken during the same point of the drive. That 18.1 is the highest I've seen on my unloaded, stock truck. That's also being much lighter on the pedal than I would like.
Forcal-
The top pic shows your mpg over the 2117 miles if you've never reset that screen. The second pic shows your mpg since you reset it 145 miles ago. The top pic display changes slower because it is averaging your mpg over more miles.
As I hit each section, I reset the MPG average. Obviously these numbers aren't long distance averages, but the MPG gauge was fairly stable, and 30 miles of the same driving style gives a decent view.
Originally Posted by joelpat
You can’t drive an entire tank on one type of road, one traffic density, one temperature, one headwind, etc. All you can do, in terms of comparing speeds and driving types, is a snapshot. And that’s all I want anyway.
Well that's why you are showing better numbers than anyone else. You are "cheating" by showing just the snapshot you want to see.
That's not how traditional MPG calculations work. Calculate it over the course of an entire tank of fuel, then get back to us. 26mpg on a 30 mile stretch of flat highway means jack crap when the other 470mi on that tank of fuel is off the highway...right? Right.
Well that's why you are showing better numbers than anyone else. You are "cheating" by showing just the snapshot you want to see.
That's not how traditional MPG calculations work. Calculate it over the course of an entire tank of fuel, then get back to us. 26mpg on a 30 mile stretch of flat highway means jack crap when the other 470mi on that tank of fuel is off the highway...right? Right.
Check your snark. I don't need it. I was not aware that there was a governing body for traditional MPG calculations posted on internet forums, but seeing as you seem to be the President of such a body, I apologize for using a format you find offensive.
30 minutes of consistent conditions is just fine to get a snapshot MPG number FOR THOSE CONDITIONS. You know, like the ones I specifically referenced in the original post. The part where I said I got 26mpg in one set of conditions, and 14mpg in another set. Nowhere did I say I was getting better overall numbers than anyone, and I don't really give two dumps what my overall number is, because the two components (city/hwy MPG) are so completely different. The MPG number to use when planning a 6000 mile highway drive is not the one that includes city driving around my neighborhood. Right? Right.
Check your snark. I don't need it. I was not aware that there was a governing body for traditional MPG calculations posted on internet forums, but seeing as you seem to be the President of such a body, I apologize for using a format you find offensive.
30 minutes of consistent conditions is just fine to get a snapshot MPG number FOR THOSE CONDITIONS. You know, like the ones I specifically referenced in the original post. The part where I said I got 26mpg in one set of conditions, and 14mpg in another set. Nowhere did I say I was getting better overall numbers than anyone, and I don't really give two dumps what my overall number is, because the two components (city/hwy MPG) are so completely different. The MPG number to use when planning a 6000 mile highway drive is not the one that includes city driving around my neighborhood. Right? Right.
Lose my number.
I have averaged 17.1 for the past 9,500 miles, which is mostly stop-and-go city driving. I've taken plenty of 100+ mile trips where I set the cruise around 55-60 and also get ~28 MPG. This is on highways in North Georgia which are not flat, but also not mountains by any means. To get the good MPG, I start the cruise control at 55 and when going up hills, I will hit the cruise minus button a few times through the climb. The minimum I'll go is 53. When I get to the top and start going down a hill I'll hit the + button on the cruise control every 5 seconds or so until I get to a max speed of around 60. This will net you 25+ MPG pretty consistently.
Majority of my time is stop and go in the city and the MPG in those situations varies from 13-16MPG for me. Going 0 MPH half the time the vehicle is turned on really hurts
I think your question is valid and I believe if you can avoid traffic, these diesels can get you 20-25 MPG @60-70 MPH if you drive smart. Is it fun? no, but it's very possible even with regens.
Not wanting to be called 'snarky', but really 30 miles of one condition or the other is not enough to really figure out what to expect for mileage. Its like saying I reset my average coming out of the Eisenhower tunnel, and averaged 99.9 MPG for the next 10 miles. Sure it's all downhill and you didn't use any fuel on the way down, but eventually, you have to go back up.
The best thing you can do for the interstate mileage, based on what you posted is 'slow down'! They are still trucks, and the aerodynamics are still very brick like. 75-80 MPG is going to kill mileage compared to 55-65.
Forcal-
The top pic shows your mpg over the 2117 miles if you've never reset that screen. The second pic shows your mpg since you reset it 145 miles ago. The top pic display changes slower because it is averaging your mpg over more miles.
I'm not sure it shows for 2117 miles in that first picture. It may be limited to the last 1000. I say that because I use Trip B, for my oil change interval, it becomes apparent that at 4000+ miles on Trip B, that the running average moves slower. I have been impressed by how accurate the Trip displays have been over the course of a tank of fuel. On most tanks, the computer reports about a half MPG LOW compared to hand calculation.
Also, shown in the first picture was an instantaneous mileage of about 22 MPG. For Forcal, this is accurate over about the last 5 seconds (hence Instantaneous).
I agree that snapshots dont provide an overall representation of fuel mileage but snapshots are useful because they show which driving conditiions maximize and hurt mpg. After getting an understanding of your trucks "mpg behavior" you can intelligently adjust your driving based on terrain and driving situation (stop n go traffic). Some may enjoy doing this for others it is a pain.
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