I drive a normally-aspirated 1988 Volvo 740 sedan with an automatic transmission and about 155,000 miles. I love my car, and it's in very good to excellent condition and has generally been very good to me. For the whole time (almost four years) that I have owned it, its gas mileage has been very consistent within a certain range: about 20-23 MPG city, and 22-26 MPG highway). Suddenly, though, starting a little before Christmas, its gas mileage dropped sharply. It's now been averaging only 17 or 18 MPG in city driving, and I haven't been on any long road trips, so I don't know about the highway mileage. It's not the end of the world, but it does mean a few more bucks out of my wallet and I'm concerned that it might be a sign of something more serious. About the only engine problems that I've ever had with my car were some ignition problems; I've had to replace the distributor cap, the coil wire, the rotor button, and the plugs and plug wires. But I haven't touched the ignition system since about September (new plug wires), which was well before the efficiency dropped. What are some things I should check to solve the problem? In general, what are some recommendations y'all have for maximizing fuel efficiency in the 700 series? Maybe I'm missing something, but I couldn't really find much related to gas mileage on the 700-900 FAQ. Please let me know what you think.