I decided that the rough ride at 65/65 was driving me crazy, almost as bad as when it was 65/80, not wanting to l set off the tmps I lowered all 4 tires to 58, my typical weekly drive that always averages 15.6 mpg increased to 19.1 with 58 psi, I thought it was going to go down not up.
I'm now considering trying 45 or 50 and see if I can get over 20 mpg.
On another note, Fuel prices have drastically increased since the election, pre election it could be had for as little as $1.69, the highest I saw it was at a Love's truckstop $2.96 but on average it is around the $2.30 range. We lucky folks in SC used to save $.40 over NC (I live on the border), but SC raised the tax on 12/1, now it's just about the same or within $.10.

 

So, you raised fuel mileage by lowering tire pressure? I had a new '10 F150 Platinum that wouldn't get but 14 mpg on the highway at 70 mph. I complained to dealer and was told it is what it is. Around 28k miles I had it in for one of the free oil changes and service they included with the purchase. The service department told me what they did and when they told me the set tire pressure at 35 psi it went over my head until I got a few blocks away. It hit me that it didn't seem right. I looked at the Pirelli tires and the recommended pressure was 44 psi. When I upped the pressure and took a trip from the Kansas City area to northwest Arkansas I got 18.9 mpg figuring gallons into miles and not the fantasy display on the dash.

So, I had just the opposite effect. When I mentioned it to the service manager he told me that he went by the Ford recommendation on the sticker at the door jamb. I found it odd that Ford would want to differ from what tire manufacturer would recommend especially after the Firestone tire and rollover incidents they had in the past.

I'm glad you found a better mileage with your new pressures but I've never found lowering pressure would decrease road resistance.

 

before the change, you were probably in the “just driving” mode; now you are in the “check fuel mileage” mode. Which is why I say if you want to check fuel mileage, drive the vehicle for at least 2500 miles or more and report milage then. In the “check fuel mileage” mode people tend to put less pressure on the skinny pedal than they do in the “just driving” mode.
Fact of human nature, whether anyone believes it or not.

 

I've been watching the MPG for a while, trying this and that, changed the pressure due to the rough ride on some washboard mountain roads, sometimes it would feel as if the truck would be sliding from side to side at 10 MPH, fastest I have been able to drive on these roads was 12-15, with the original "per spec" of 65/80 it was like an old carnival ride.
At 58 I was actually about to do 30 without feeling like we may go off the side of the mountain.

 

You should set your tire pressure based on what the decal on your truck's door jamb says and/or what's in the owner's manual NOT the on the tire:

The tire manufacturer states: "MAXIMUM RECOMMENDED PRESSURE X PSI", they have no way of knowing what vehicle the tires are going on; a 1/2 ton truck will have different tire pressure requirements than a 1 ton truck with the same size tire (heck I've even seen metric sized LT tires on a Tacoma and running the Max pressure printed on the side of the tires in that truck would be like riding a buckboard!). Unloaded 35psi in a 1/2 ton truck is probably safe; the decal on the door jamb is good starting point then using the chalk method in a parking lot will help you get the best pressure for longest tire life and maximum tire performance. Running around Over or Under inflated will lead to uneven tire wear and you won't get the maximum life out of the tire.

 

To me its more about the ride than the tire life, if I inflate to what the sticker says its like driving on solid tires and I feel a toothpick in the road, if I have to replace the tires twice as much but have a good ride it is worth it to me.

 

You do yours and I'll do mine.

 

I had a friend that had a early 90's 2500 Dodge with the Cummins. He found out by accident that keeping around 100 lbs in the rear of the bed got him 2 miles more MPG. The rear tires weren't bouncing off the road all the time when empty.

 

I've had up to 500/600 lbs in the bed and it seems as if the truck laughs at that, but I get it that a dodge would be affected HAHA

 

___________________________
All you are doing when lowering the tire pressure is reducing the circumference of the tire........ You have 'tricked" the electronics in the vehicle to think it is going farther on fuel.

Fill it up at point "A" ........ Make your weekly drive and fill it up at point "B".......... do that with max air pressure and next week do it at minimum air pressure.... Was there a difference in the amount of fuel used ? disregard the electronics when you do this test.

Hobo

 

Manual calculations, although the electronic is within .1 MPG so I consider it pretty damn accurate

 

I am not sure about that Hobo. The rev's per mile are unaffected by air pressure in the tire. Ride height is affected but not revs per mile and that is what affects mpg.

With lower pressure the sidewall will flex more creating a less round surface as it spins but revs per mile will be unaffected. Becomes more of an oval at that point when the sidewall is flexing.

Either way, less psi will never give you more actual mpg. The opposite is true in all cases due to rolling resistance.

 

Cool deal. I run 40f/45r on my ccsb. There’s absolutely no reason to drive around with over 50 psi unloaded. Talk about riding like the flu stone mobile. Drop the psi and soften the ride until you tow

 

Something to keep in mind, particularly with SD trucks is that by using the tire pressure stated on the B pillar will allow you to tow/carry what ever your GVWR is. If you’re driving around empty the tire pressure can be less, sometimes much less...
Carli suspension has a page on their website that says for SD truck running empty something like 45/65 will work (if I remember correctly). I usually run mine closer to what is on the sticker as an frequently carry loads.

 

I tow on occasion, refilling to specs when I do isn't a problem. Going to fire up forscan and lower the thresholds then the pressure to 50 and see how much more it improves the ride which was the original intention, getting better MPG is a bonus, fuel went 10% up again yesterday, I'm assuming we will be at $4 +/- by the end of the year.