I think your focussing too much on fuel economy and not traction. We've both driven Saskatoon streets to know what they're like. If I was in your shoes right now I'd be looking for a good set of winter tires instead. Get a good set of Michelins in the summer. I'm not quite sure how truck tires are on a car (never tried).
Not quite sure how an air filter will lower RPMS at cruising speed.... but okay.
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