I have an 01 V70, but very basic and similar to your machinery. I run Mobil almost exclusively, and get about 30 mph on my daily commute at very slow speeds. I avoid Irving for political reasons, they are the Walmart of oil companies. Consider regional variations in gasoline formulation. Last fall we took Jr to college in Minnesota, a 3400 mile round trip. Started out on a tank of Maine summer formula, that ran through at about 28. Car was stuffed to the roof rails. As we made westerly progress, the mileage improved. Maybe due to extended highway miles, but most likely due to different fuel formula. I was told that Minnesota has 10% ethanol, and that I would get lower mileage. I didn't. The best gasoline was the last tank, purchased outside Montreal, PQ. It ran through at 34mpg, and that was mostly on two-lanes across Vermont and the Kangamangus Highway in New Hampshire.
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01 V70 2.4 M5 and a Mini