I'm curious how the "recalibrated" the speedometer.......

 

It must've been a helluva fine recalibration to convince a guy that a second generation Ram with a 5.9l V-8 just saw 18MPG at 75MPH. Astro-freakin-ominal job there:

 

I want that calibration too!

 

I don't. My speedometer is already off and I don't want it made worse!

 

The best mileage I have ever seen on my truck was 20 mpg. That's hand calculated 100% highway going about 60mph. my bed was loaded with about 600 lbs (dirt bike and atv).

I got 265 tires, cat back flow master 40, $40 ebay CAI.

Keep in mind I consider myself an expert fuel saving driver. low rpms, consistent speeds, slow acceleration, accell on downhill roll uphills.

I get 15mpg with 50/50 highway and city almost every tank. but I can never be in a hurry and have to pick my routes carefully to avoid big hills. Keep in mind I'm from Canada where gas is $1.25 a liter for 87 so being fuel smart is a must.

I don't think your computer is accurate if your going 75mph.

edit: my cat and headers are being installed right now so don't mind the signature.

 

Before I left for my trip back home, I filled up and calculated my mileage that way, and it was 17.2 mpg, on my way home, I set my cruise at 75, and used my gps to compare speeds, gps read 72 while speedometer read 75, not sure how big of a difference that makes. Once I got home, I filled up and calculated my mileage and got 14.8. I looked up and found out that there is a difference of about 200 feet between where I live and my inlaws house, about 70 miles away. So going there was all down hill and coming home was all up hill. Still happy to see almost 15 mpg freeway. I'm still looking to improve it a bit, so any suggestions would be helpful. I'm not the most mechanically inclined, but I do have a couple mechanics that help me out when i need it

 

agoodman, just so you know, as you cannot always tell by what is posted, recalibrating speedometer in these trucks si not something a tire shop would do. To change the speedo in these, you have to reprogram the PCM - and I'm can't think of a tire shop I would want to do that on my truck. If they told you they did, they were not being truthful most likely.

 

It wasn't just a tire shop. It was the shop that I bring my vehicles to when I can't fix them on my own, and they happen to do tires as well. They fix pretty much anything on vehicles, including reprogramming computers, as they have done this on my wifes car. I talked to the owner of the shop tonight and he gaurenteed speedometer accuracy, and if its off, they will correct.

 

When i got the tires, I questioned whether the size difference would affect anything with the speedometer, they assured me that they would make sure the speedometer was accurate b4 I got the truck back. I don't deal with shops that just sell tires, just like I don't go to oil Change shops. I prefer to go to shops that can fix just about anything on my vehicle if need be. Makes life easier for. I paid the same for the tires there as I would have at a tire shop, even if I had to pay more, id be ok with it. They never charge me labor when they work on my vehicles, so ill always give them my business

 

Four percent. Your odometer miles are running four percent high, that is. Sounds like the truck was calibrated for those 265's and not adjusted for the 245's.

Using odometer mileage? If so, adjust downward by 4% so you got an actual 14.2MPG. That's about right for a stock 4WD 5.9l in a good state of tune running 75MPH unladen on properly inflated tires and with a properly aligned front end. If yours is 2WD instead, 14.2 is a tad low.

The biggest determining factor of fuel economy (lack thereof) in these trucks is that we're bucking a coefficient of drag that's right at 0.48 for a 4WD club/quad cab short bed, with 36 square feet of frontal area for the 4WD (about a foot less for 2WD), with two and a half to three tons behind it. There's only so much that can be done with that configuration and the engines we've got to work with. You can squeeze another 1.5-2MPG out of it by tuning, eliminating parasitic losses, and going easy on the skinny pedal, but that's pretty much where you can expect to hit the wall just because these trucks are big and heavy.