Really good MPG

[Andres]

I'm taking my '06 Dodge Ram 3K miles (pulling a Hummer on a trailer) this weekend and decided to check the tire pressure. Truck is stock with a Quadzilla 65hp chip. (Hummer has a '03 ISB305 w/a smarty and boost fooler. )



Dodge stock Michelin tires are 46psi all around, just like it was when I bought it new. Tires say 80psi max cold. Hmmmm.



Door says 60front/45rear unloaded, 60front/70 rear loaded. Its a 2500 w/factory Michelins. The tires still have lots of tread left.



My normal freeway mileage (according the overhead console )is around 21. 5 unloaded. I get the same with the odometer and a calculator.



I filled front and rears to 60psi and drove 40 or 50 miles to buy a new CB.

With the a/c on, cruising at 71mph, the mileage crept up to 27. 4mpg.

It stayed between 27. 3 and 27. 6 the whole way home.



This is a quadcab with a toolbox in the back full of pretty heavy crap.



This morning I boosted the pressure in the rear to 70 psi (Im loading the trailer tonight), and unloaded, the mileage crept up and maintained around 28. 2mpg for 120 miles of freeway driving.



After my 3500 return trip, I'll do some testing and record the results, but this seems to good to be true.



I feel like an idiot for not looking at this a year ago. I am guessing that the dealer sells more trucks test driven at 46psi, than at 60. Yes I realize that wet weather performance will suffer at higher pressures and nI need to pay close attention to tire wear.

 

[SHovis]

If you ride a bicycle with low tire pressure, then inflated the tires to a higher psi, you will notice a huge decrease in rolling resistance as measured by how much effort it takes to pedal the bike at a given speed. Has to be the same for a vehicle.



Also, adding air pressure to the tires increases their height somewhat, which may have an effect on the mpg computer calculation.



Steve

 

[betterthanstock]

Agreed. I just assumed that 46psi was "reasonable" and that one couldn't get huge gains going to 60psi. Anybody with similiar good or not so good experience?

Go by what the door says.

46 is good for big tires, 315/70/17 or 35 inch x 12 wide. It's too low for stock tires. Too bad they underinflated them. Maybe they want it to seem more comfortable on the test drive.

 

[RKerner]

When I increased the air pressure in my stock Michelins from 45 to 80psi, I gained about 1/2 to 3/4mpg. Your mileage gain is very optimistic or it coincided with the wind always being at your back.

 

[ronman]

Man-o-man what I'd do for that MPG on my '06... Best I got unloaded/not towing was 19. 7 at similar speeds with about 3K miles on it. Could Quadzilla be doing THAT much for fuel economy??? Is your truck 4x4? Stick or Auto?

... the mileage crept up to 27. 4mpg.

It stayed between 27. 3 and 27. 6 the whole way home... .

 

[JHardwick]

With the a/c on, cruising at 71mph, the mileage crept up to 27. 4mpg. It stayed between 27. 3 and 27. 6 the whole way home.

I'll be the first to call bull****. Better sharpen that pencil!



BTW, what radio did you get?

 

[cclark746]

im with hardwick i have owned four 3 gen dodges and know many people with them i have done many test with and without chips and the overhead console is never close to the actual mileage. especially with a chip fooling the fuel system i know that you said you did it by hand but to get the same thing the computer is saying huh. it has always been way more on every truck i have ever owned, and then when adding a chip the gap becomes even bigger. i am not saying you didnt increase mpg with airing up the tires but after owning several 3 gen dodges i dont see you getting that kind of mileage even with a Hurricane Rita pushing you.

 

[betterthanstock]

Are those 27 mpg Canadian gallons? That would make it about 22 US mpg.

 

[cclark746]

still with just a quad box and the same stock auto trans i got in my 06 which doesnt even come close to 22mpg unloaded and i have the smarty which after many different chips and programs found that it increased mileage the most. i will be lucky to 16. 5 to 18 unloaded highway driving.

 

[Hasman06]

Ditto, the more add ons you put on, the more the overhead will lie. Ive seen awsome numbers right up until I do the math. No freakin way your'e getting those #'s (U. S. ) when you put it on paper. Stock my 06 was 2-3 mpg overstated usually, now with add ons, I've seen as much as 5-6 mpg overstated.

 

[JTurk]

Basically, look at the overhead as a woman's toy!



I also have a Quad on my 3500 dually. I run the recommended 65# and can get the overhead to read anywhere between 20. 4 and 25. 7. The real calculated mileage is between 16. 5 and 17. I've also found that the error is greater running at 75 than at 60.



By the way, I just retired my original Generals today with 52. 5K on them. Replaced them with another set of the same!

 

[DerekW]

If you ride a bicycle with low tire pressure, then inflated the tires to a higher psi, you will notice a huge decrease in rolling resistance as measured by how much effort it takes to pedal the bike at a given speed. Has to be the same for a vehicle.



Also, adding air pressure to the tires increases their height somewhat, which may have an effect on the mpg computer calculation.



Steve

lol my bike tires feel like they are filled with concrete they are so hard. but my goodear mtr's are bumped 10 psi over the 65 psi sidewall rating on the tire. i i did this bump up mileage some and decrease load on my broke 2 speed with lock up 48re. but then again aint too much mileage to be gained with out an overdrive, big injectors and alot of rpms at 55, 65, 70 mph.

 

[Turbo_Bob]

Dodge stock Michelin tires are 46psi all around, just like it was when I bought it new.



Door says 60front/45rear unloaded, 60front/70 rear loaded. Its a 2500 w/factory Michelins.



My normal freeway mileage (according the overhead console )is around 21. 5 unloaded. I get the same with the odometer and a calculator.



I filled front and rears to 60psi and drove 40 or 50 miles to buy a new CB.

With the a/c on, cruising at 71mph, the mileage crept up to 27. 4mpg.

It stayed between 27. 3 and 27. 6 the whole way home.



This morning I boosted the pressure in the rear to 70 psi (Im loading the trailer tonight), and unloaded, the mileage crept up and maintained around 28. 2mpg for 120 miles of freeway driving.



After my 3500 return trip, I'll do some testing and record the results, but this seems to good to be true.

I need to pay close attention to tire wear.

My truck and stock tire combo says 45 front, 40 rear unloaded. I have changed to 45 all around long time ago. My tires are wearing perfict, I have 92K on the truck with the same tires and brakes. When you pump up the tires too high for the load you will get two problems, bouncing ride and center tire wear. Yes, the MPG will go up, but I dont see it helping to the extent that your overhead mpg is telling you. I have seen my overhead get into the 30's after fill-ups. But when you go through the whole tank the overhead is more in line with the actual math of gallons added/miles driven. I get a 22 to 23 mpg consistant during each fill-up solo.