I guess since I got the 555, that pretty much sums it up. I had a 600 3500 on order, but bought a used 555 2500. Since the only difference was the helper springs and clearance lights (which sometimes leak), I decided to spring for this used one. The 555s weren't available in CA, so it was somewhat unusual for me to find one on a lot equipped the way I wanted close to my house.

I'm very happy with the truck, but I know a 600 would have been just fine as well.

 

My third tank got 18.5 MPG highway and 16 city. It now has 1500 miles on it and the mileage is going up. Just loaded up the truck with 2000 lbs. and drove it a couple hundred miles up the mountains. I am hoping the mileage increases with the rings seating increasing compression and less blow-by.

Blair

 

If I could do it all over again, I wouldn't change a thing. I have the 555, it pulls great, good mileage (19-21 hwy)(17-18 city), and no vibration yet. I test drove the 600 a month ago just to see what it was like, and I could not really tell any difference in the power so why not go with good fuel mileage ! Just my .02

 

dwhite I love 04.5 gust hit 10K on the clock19 mpg Hwy. 16 in town now my Friend has the 03 way to slow and noisy at stop lights.

 

"If I could do it all over again, I wouldn't change a thing. I have the 555, it pulls great, good mileage (19-21 hwy)(17-18 city), and no vibration yet. I test drove the 600 a month ago just to see what it was like, and I could not really tell any difference in the power so why not go with good fuel mileage ! Just my .02"

What he said!! I drove both and couldn't tell any difference. I couldn't see going with the cat when I didn't have to. One less expence to keep up for the EPA

Bud

 

well i know of 2 friends that claim 18 mpg on there 600s one is a 4x4 both 6 speeds. mine is doing great! 20 in town and 22.5 to 23 on the road empty, I love it my wife wants to trade her new car off and buy her one with the auto of course she love mine except for the stick, glad I didn't get the auto i'd be driving a car right now!

 

 

we love our o3 2500 st qc 555 6speed 4x4 my wife drives it almost asd munch as i do now fore some tires and lift .

 

Averaged 21.05 mile/gal on 3 tanks over 1700 miles. The overhead read 22.2-22.6 at the end of each tank. Not really sure why the overhead is overstating the mileage. I commute 45 miles to work. I set the cruse control at 62 mph for as much of the commute as possible.

I have measured earlier tankfuls driving faster. Cruse speed 68-72. Mileage at fast pace was 19.2. Based on these results, I like to find taller but narrow tires to yield a higher gear ratio. Maybe I could drive 70 and still get the high mileage.

Pulled 7x20' gooseneck stock trailer 120 miles round trip. Reset overhead reported 13.4 for the trip. This short trip did not support a hand calc.

That was lower than Dad get with his 2001 Powerstroke pulling the same trailer. I can live with it because he only gets 17.3 unloaded.

My truck is an '03 555 with 6 speed 4x4 short bed with just over 9000 mile. I bought it in early May with 3000 miles on the od. It was a re-paint job. I was not looking for 600 due to the reports on this forum about the 600's lower milage figures.