Poor Fuel Economy. Any solutions?

[Mr 5 0]

According to your numbers, last year you were getting about 17 mpg, now you're getting 15.5.

Not a huge drop.

A number of factors could be involved, assuming you do exactly same kind of driving this year as last.

If you do more in-town (stop and go) driving, your gas mileage will drop.
If you need a tune-up (plugs, especially) gas mileage may drop. If you've put a lot of miles on the car - and resultant engine wear - gas mileage may drop. Carrying more weight in the car or even a tire change to one that has a softer tread compound might precipitate that 1.5 mpg drop you've experienced.

Lots of variables here and any combination of these could explain a 1.5 mpg drop, including a colder winter, as colder temperatures make the engine work harder and reduces gas mileage.

Finally, your gas gauge could simply be off a bit (they usually are) and this has skewed your mpg calculations.

As you've had the car diagnosed and it came up fine, I suspect some non-mechanical factor or a combination of small things to be the cause of the slight drop in gas mileage and I wouldn't be overly concerned.