Ok, I ventured inside the beltway today... I went to Alexandria. Got pleanty of practice DFCO'ing at traffic lights in a completely urban environment. By carefully and progressively downshifting I can keep DFCO going down to about 5-10 MPH. SG was reporting 18 MPG average on my urban driving with DFCO. Not sure how accurate that's going to be because I've already established that SG doesn't know what's going on with DFCO in my truck. Going 55MPH on urban highways inside the beltway have few opportunities to DFCO because of heavy traffic.
Once I got on the toll road on my way out of town I again set the cruise at 60. I'm thinking 60 is probably the most efficient speed in the truck. I used to think that the slowest speed possible and still be in OD would have been best. I don't think so now. If you touch the pedal, or loose speed it drops down to 3rd gear - something we want to avoid. 55 is good, but its borderline whether or not DFCO will kick in when the cruise lets off the throttle. @ 60 you are going fast enough that you can stay in OD, even if you give it some throttle or loose some speed. Plus 60 is fast enough that if the cruise lets off the throttle for more than 3 seconds it DFCO's. There was one stretch where I was able to maintain DFCO for almost a whole mile.
I'm still wondering if there is some setting in SG to make it realize I'm in DFCO and reflect that in the instantaneous mileage.
one thing I have been told about the scangauge is that it uses air flow to get MPG readings so the engine is still pumping air through it with DFCO. I guess that is the big reason that the scangauge doesn't always see DFCO.
I just use the scangauge as an indication tool anyway. wait until the tank gets filled again, that is where it really matters in the end.
Be the change you wish to see in the world
Yes, the SG is a tool to help me. Right now I'm using it in ways I never considered when I bought it a month ago. If you told me a month ago I'd be watching my O2 sensor output, and really caring what the numbers were while I was driving I would have said you were crazy.