MPG not what I expected

[JMarkos]

We just returned from a 1000 + mile trip to Las Vegas, 1036 miles, no trailer, 75-80 mph, no head wind to speak of, average was 17. 7. I don't get it, I get 19-22 driving back and fourth to work. Anybody have an explanation on this, I really expected to 23-24. Thanks

 

[Todd G]

At 80 mph, your truck has the aerodynamics of a brick. I find that I lose 5 mpg between 70 and 75!

Do you drive at those same speeds going to work? I doubt it.



Speed kills MPG.

 

[Archive]

Todd is right on... if you want your mpg to go up, back out of the throttle... you aren't going to get both.

 

[JES]

I just did a SF/CA to Denver & back trip at 85 to 111mph. this was across Hwy. 50 and the back roads of Colorado. I got 17. 4 mpg and thought I did GREAT! In town on the slowways of sillycom valley I get 15. 7 most of the time.

 

[JMarkos]

I don't see how you can go much slower than 75 with out causing a traffic jam, I was sllready getting passed by semis. I guess next time we will plan an extra day for travel, I would really like to see mid 20's.

 

[Ragin Ram]

I wish I could break 17 mpg. Mine seems to be getting worse. I'm beginning to become suspicious as to whether the dealer did the dreaded re-flash when I took it in for the clock spring recall. Did you happen to take it to the dealer for any service?

 

[BCFAST]

MPG's

Not very knowledgeable about your overvalved motors, but the P7100 pump seems to have a very defined fueling curve. Somewhere between 2050 and 2100rpms, the fuel curve goes waaaay up and the mileage goes in the toilet... . as someone else pointed out, to the tune of about 3-5mpg!! I guess it's sorta like finding out where to shift in different vehicles; some you can just feel the motor fall on its face at a certain rpm. I'd love to have a US Gear overdrive and be able to run 80mph at 1900rpm... but the $2k would take a long time to recoup in fuel money. Oh well. . I can dream, cant I?

 

[Todd G]

With my 4. 10's and 33" tires, at 55mph I can get 20 mpg.

At 65 mph - 17mpg

75 mph - 14mpg!



There are times when I wish I had 3. 54's. Most times I don't.

 

[Shelby Griggs]

Won't Happen

Originally posted by JMarkos

I don't see how you can go much slower than 75 with out causing a traffic jam, I was sllready getting passed by semis. I guess next time we will plan an extra day for travel, I would really like to see mid 20's.

I don't think you will ever see mid 20's at over 65 MPH. I notice my best mileage is at low RPM's, which puts you in danger of lugging, if you are pulling or going up hill. These trucks are heavy and not that aerodynamic. Since Oregon has a 55 MPH speed limit still, I can get away with slower speeds, and have found that my best mileage occurs between 58 and 63 MPH. If that holds up traffic, too bad, I will not exceed the speed limit by more than 9 MPH (OK maybe to pass ) There are way too many radar using traffic units here to risk that, and they do enforce the law at the 10-15 MPH over area. On level ground in town, a 5th or 6th gear selection at 45 MPH gives awesome mileage, but you would never get anywhere at that speed on a trip.



I have actually seen my best mileage in the mountains at variable speeds and grades. It seems that mileage rarely drops below 16 MPG, in mixed driving, and I see a lot of 99 MPG on the downhill. This tends to average higher than a sustained 18-21 MPG which is about all I ever see on the flats.



IMHO the key to better mileage is smooth starts and stops using the least amount of brake and throttle to get the job done, and then a steady but slower cruise speed.



I will be making a trip to California from Oregon the week of the 20th, if I get 20 MPG I will consider that good. I once hopes for 22-24 MPG on the highway, but I don't think that is in the cards.



Shelby

 

[Midnite]

Originally posted by JMarkos

I guess next time we will plan an extra day for travel, I would really like to see mid 20's.

I have a very realistic recipe for you if you would like to see mid 20's:



1. Remove your side mirrors

2. Remove any running boards/nerf bars

3. Remove any fender flares

4. Remove any mud flaps

5. Remove any sun visor type add-on

6. Remove any aftermarket bumpers

7. Remove any aftermarket driving/fog lights that do not fit within bumper openings

8. Use 215-85R16LT tires (narrow + tall = less rolling resistance)

9. Use synthetic oils wherever possible

10. Never exceed 65 MPH unless going down a hill

11. Shoot only the *passenger* side tires of slow moving vehicles in front of you. The drag will work with the crown of the road to pull them to the shoulder more quickly.





Obviously number 11 is not the only unrealistic item in the list. However most of it is generally true--the biggest thing is that our trucks DO have the aerodynamic qualities of a poorly formed brick. Slower is generally better where milage is concerned. (as long as you're in your top gear, and you're not lugging, of course) Remember--aerodynamics is king!



Granted I have a 1st gen, but given my auto transmission, I would expect my best milage to be between 50 and 60 MPH (3. 54 gears). If I had the good fortune/lottery winnings to be able to afford a Gear Vendors or US Gear overdrive AND a DTT torque converter, I could probably hit mid-20s MPG at around 60-65 MPH.



Mike

 

[DarrellB]

Great Mileage

Just got back from a trip to Northern Indiana and averaged about 22mpg running anywhere from 60mph to 85mph with 4:10 gears.





That Mileage is unloaded just my truck and a full tank of fuel.



Who needs 3. 54 gears

 

[Vaughn MacKenzie]

JMarkos, another thing to consider is the temperature, running in very hot weather can cut your mileage a bit, especially if you're doing 80 and working your truck hard.



Cruising southern Nevada in 110+ last week I got good mileage on the highway, running 75-78 most of the time, occasionally cruised right at 80. Coming home I saw 22. 2mpg (note I have 2wd). On the way down it was about 20 due to strong headwinds. But running around LV is a mileage killer, mine dropped to about 16 there (usually 18-19. 5 at home in town). Sure was easy to make billowing clouds of smoke with the DD2s!



Vaughn

 

[Archive]

Re: Great Mileage

Originally posted by DarrellB

Who needs 3. 54 gears

LOL. Not me!