Hey, where abouts in Canada?

If you have poor fuel economy, I would first be looking at the air filter. Make sure its clean and in good shape. What kind of fuel are you running (brand and octane). When you installed the new plugs, did you gap them correctly?
You could deff try Seafoaming the engine. Check/adjust your tire pressures...if your still running your winter tires, take them off, put your summers back on, I dont think we are going to see too much more snow.

Jay
(Ontario)