Getting the parking brakes properly adjusted is not easy. First and formost is getting the star nut on each wheel correct. I had a heck of a time with my AWD because the wheel can only be rotated forwards AND I could only get the rear wheels off the ground, not the fronts at the same time - limits travel due to the prop shaft.

When adjusting the star nut inside the 'drum', tighten it until it stops. Then loosen 2 clicks. Make sure the shoe is no longer rubbing. Do exactly the same adjustment on the other side. If you have to go 3 clicks on one, then do 3 clicks on the other.

Then tighten the brake handle.

From your description, it sounds like one side is tighter than the other. Also, give it time to 'break in' by driving with the parking brake on/rubbing for about 100 feet or so.

As to the mpg, it should not have changed. You should have easily gotten 25mpg at that speed, unless you had a headwind. Hilly doesn't count, because downhill will make up for the uphill stretches.

Klaus
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Volvos should be saved from the junk yards, not donated.