I had a similar issue as I wanted the QDII but didn't want or need the V8. I ended up buying the V6 with the QTII but I have not had a chance to put it to use. I'm sure the V8 with the QDII is very nice but I'm not sure how much that affect your gas mileage. Gas mileage is the main reason I ordered the V6 based on reports of gas mileage from other V8 owners.