Ever since I got the Customer Satisfaction Program 12B34, my fuel mileage went down. I use to get 11 +/- when pulling my 14K 5ver and 17 to 19 non-towing. I've dropped at least 2 mpg on towing and non-towing.

The dealer said I need the flash no matter if my truck runs good with no problems. So, I got it and can tell absolutely no difference other than crappie fuel mileage.

Has anyone else experienced this situation.

 

12B34 is for the chassis-cab truck (F450/F550) with the conventional turbo.

I updated it a couple of days and 250 miles ago. Sure, not a lot of miles to show a significant difference in mileage. It feels as it might have gone down a little but the jury is still out.

However, I very much like the much improved shifting and better dead-start response. Dead start acceleration is responding quicker and once taking off, a lot more "measured". I used to wait for seconds on a green light with no activity and then just about leaving rubber. Now, it starts quicker and smoother.

Shifting is more "aggressive" (slightly higher shift points) and that is most likely where the fuel mileage drop (if any) comes from. I also noticed a change in "power curve". It seems more "peaky" starting from about 2300 RPM up, but feels like less power below that. I also noticed that the turbo boost has gone up by about 2 psi. I now regularly reach/peak at 28 psi during acceleration.

Another interesting change is the downshift during slow deceleration approaching a red light or whatever while in NORMAL transmission mode. I noticed that based on SPEED (not RPM) the tranny shifts down from 6-5-4-3-2-1 which is great because if for example the light turns green and you want to accelerate, it is already in the correct gear. That one is new to me and I sure like it.

I believe they moved down the de-fuel point reacting to exhaust temperatures that may be a bit lower than before. That would make sense since one of the items they tried to fix is turbo blade failures.

 

This tsb also is for f350 chassis cab and mine goes in on Monday. I have been discussing this recal with another member who had it done on a chassis cab and he has noticed no difference in fuel or truck behavior. I will update when mine is done.

 

I seem to have lost a little over 1 mpg after the update, but it could just be my driving habits. When I first brought the truck home I got about 18 on a 7+ hour drive home. I was working out of town and on flat land in North Carolina and was averaging 16-17. Now I am back home in the hills of Tennessee and am getting about 14.5-15. I really drove it gently when I first bought it, but now I drive it like I own it. Anyway, after the flash it seems to run better, but I do believe I lost about 1 mpg.

 

12B34 is for chassis-cab only. Pickup configurations receive the 12B33 update which appears to be a lot more extensive. See reference to 12B34 by Ford:
https://docs.google.com/open?id=0B33...WRTY0FKQWxhd00

 

I lost about 1-1.5 mpg after the reflash. Not thrilled at all.

 

I've only burned almost one tank so I still need to do more testing.

I am at 13.5 most of the time and I'm at 12.6 currently after the flash on Monday.
So, same driving conditions and less MPG so yes mine seems worse but I need to burn a few tanks before I consider this an issue.

 

Mine was about 1 mpg better but has leveled off to where it was pre-flash. The dead-stop response and overall acceleration is worlds better. Towing mpg is 1 mpg better...go figure?