Barry, that'* probably about right. It wasn't super windy but IIRC you would have had a 10-15 mph crosswind. That'* enough to effect mpg'*, so 31 mpg in those conditions is not bad... If it make you feel any better the best I've gotten on the freeway at 70 mph in my current 99 SSEi was 22 mpg. :(
I am going to get another CASE Learn procedure done in the next few days..... I have a feeling the one I had done when the new motor was put in wasn't done properly, or else it'* my ZZP PCM.
My parents just got back from their weekend trip to Duluth in their 2002 Buick Park Avenue Ultra (3800 SC'ed) and they got the best they've ever gotten MPG-wise -33.8 MPG, but they were cruising at 65 mph. I had swapped their stock airbox back in before they left..... made me wonder about the effects of a custom intake..... I used to get better mpgs with a custom intake, but the past 12-18 months it seems to have reversed, but then again the past 12-18 months I have been running them on different vehicles than in times prior to that.