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Can somebody please tell me where I can find out more info on this matter. I'm not sure if my truck has it & if so how it exactly works. I have a 2004 chevy Colorado 2.8l 4 cylinder automatic trans. I just started hypermiling yesterday after a day of researching.

I'm sure it does, but without a Scangauge, it would be hard to see. Do you have an instantaneous mpg display? If it goes to 99mpg or whatever your top scale is, it is probably in fuel cut. My 96 Mazda B4000 (Ford Ranger) does it coasting down to 50 mph in OD. If I take the OD off at 51mph it will stay in fuel cut until about 35 mph. If I manually shift to second, it will stay in even lower.

That's very interesting.... How do you know the fuel is cut?

The mpg goes to 9999 mpg and the gph (gallons per hour) goes to 0.00 or 0.01 gph.

The ScanGage can also be set to display "open loop" (DFCO) vs "closed loop" (fuel mixture set by oxygen sensor reading).

My recent GM cars needed to be shifted to third gear manually (move the lever from D to 3 in your truck) and engine speed had to spool over 2000rpm before fuel cut would start, and it would drop out when the tach dropped to around 1500. In D and 4th gear, it would freewheel when coasting. Your truck may be different, though, so it is best to experiment with a ScanGage to find exactly when the injectors are cut off and when they come back online.

If your truck needs to be downshifted for DFCO then it is best to use it only instead of the brake (traffic permitting) for downhills or slowdowns ahead. Otherwise, is not too useful on flat terrain because of the loss of forward momentum.

Thanks once again. I will have to get a scan gauge. I realized something last night.... I don't have od.

Thanks once again. I will have to get a scan gauge. I realized something last night.... I don't have od.

Your 4th gear is the equivalent of OD.