A few days back I posted regarding my 88 245A feeling sluggish. I had replaced the fuel pre-pump about 6 weeks earlier, it ran peppier, then seemed sluggish again. After checking suggestions from Brickboarders and not finding mechanical issues I think I solved the problem: It's the gasoline! To make a long story short, winter formulations have lower energy content. I usually run 89 mid grade (Shell or Chevron). I added about 3 gallons of 91 premium to top off the tank, drove it awhile and the pep returned. With a meager 114hp, anything that helps is welcome...

The reason that the higher octane gasoline added a little pep is because your engine has a knock sensor that continuously tries to advance the ignition timing while you drive until it hears knocking (pinging), then retards the timing slightly. On higher octane gas, it can advance the ignition timing a bit furthur, thus improving power slightly. Just another Volvo advantage!