Had an interesting experience coming back from Myrtle Beach a few weeks ago.

Generally, I don't trust the overhead for fuel economy numbers, it generally reads 5-7% high. However, towing my camper, one of the tanks actually was perfect.

Here is the situation:
~510 miles each way. With the trailer on and running I-95, I got about 315 miles on the first tank. Filled up in NC (only put in about 33 gal, I can get in 39 if I run till DTE hits 0), so till I hit Myrtle Beach, I had ~1/2 a tank.

I've been running 15oz PS, with 9oz of MMO everytime I fill up...I read the back of the bottles, and brewed that ratio and amount based on a 200 gal tank, I think. (One of them says the bottle with treat 100-300 gal, so I split it down the center...I forget what the other one said.)

Before we left to come home, I filled up again. However, I only had 24oz bottles with me, and I wasn't thinking until it was too late...I had dumped the entire 24oz in, and only put in about 20 gal of #2.

So, coming back north, I had to stop near Richmond to fill up. I noticed various times through that tank that the overhead was reading much lower than it was on the way down. I just figured it was traffic, etc.

Anyways, once I filled up, I did a quick hand-calc, and I came up with 9.73, where as the overhead had read 9.7.

So, I guess what I am asking is if anyone else has noticed what happens if they load up the PS/MMO. The mileage was down (~0.4 mpg) from the 1.5 tanks I ran on the way down, but that could be traffic, speed, etc. But, the overhead was dead-on.

It's weird stuff like this that keeps me up at night!

 

when i got my 06 Dodge a few month ago the overhead MPG was right on.with a programer its OFF!!!

with the fuel ad. i do seam to get better MPG and power.I also look for BP 45c fuel.

 

My 04.5 used to run really good with just the PS. I would definitely get better performance & mileage using it. I also would overdose using the PS.
Don't forget, coming back UP north you're heading UPHILL!! Mother earth being round and all. Used to see the same thing when I was traveling from PA to FL two times a week.

 

You can add to much PS and lose mileage, also called over dosing. My self I will no longer use PS as it had a large amount of Naptha in it aka lighter fluid. I now use Lucas and have been very happy with it and I see a small increase in mileage when I use it. Many of the pre 2004.5 engines do well with 1 qt of ash less 2 cycle oil per 32 gallons of diesel so you may want to try using it instead of PS.