I don't really have recent solid fuel mileage numbers before and after the plugs. I'm pretty sure before the plugs I was getting anywhere from 17mpg to 21mpg in the city. I've only had to refill the tank in city driving a couple of times since the plugs and I did not run the numbers, but I did notice much higher readings on the trip odometer that what I've become accustomed to. I've so rarely driven my Volvo's on long trips, I really have no other current info that I got about 31mpg in the 960 on that trip after the plugs. There was no change in power or smoothness though.

For several years the most mileage I've put on any one car would be less than 3500 miles as I do not commute to work. As of two years ago, both Volvo's have seen under 1000 miles a year. That's because I bought a Miata and it quickly stole the whole show, I've been averaging 10k miles a year on it and that's all recreational driving
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'92 240 @45k & '96 960 @41k