Change in gas use

You have a North American GenII, you have a fuel bladder. There is no accurate way to hand calculate tank by tank fuel consumption. The whole premise of dividing miles driven by gallons added relies on the tank being the same size. So you know how many gallons you put in because you know you had a full tank before and a full tank afterwards, and you know how many miles you drove, easy. On the GenII NA Prius, the "tank" is variable. So you know how many miles you went, but when you fill up, you have no idea how many gallons were in there the time before, and really you have no idea how many gallons are in there now.

Is 44mpg about what you always got? Or did you use to get 50's and now it is 40's? If you drive with non-LRR tires at factory pressures, keep up with traffic, and drive on the interstate, 44mpg displayed on the MFD is actually about right.

If you can find a nice stretch of highway, make sure your tires are pumped normally and then drive up and down about 20 minutes each way at 55mph, you should average about 48mpg to 50mpg.

There are way too many variables to say whether or not the engine should run when accelerating. If the engine is warm and has reached S4, and the power demand low, and temperatures are good, then under low acceleration you should be able to "creep".

 

Suggest you fill this out:
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

and post in the Fuel Economy forum

 

^^^
Yep. Please fill out the questionnaire.

And agree w/2k1toaster's post. The bladder tank causes a lot of variation in manual calculations. The only way to get numbers via that is to average it over many tanks. Some values will be way below the MFD's reading for a tank and the next will be way above. It tends to alternate (e.g. 1 way below, the next is way above).