I bought the press on 3.4" Pulley from GrandPrixstore.com
Make sure you also invest in the puller tool.
I was surprised at how tight it was and would never attempt it without the proper tools.
When it finally broke free, it cracked like a broken bolt!
Too many short trips to notice any difference in mileage. I have always averaged 14 - 17 Liters per 100 Kilometers (14 mpg) in this mountainous terrain where the traffic flows at an even 60 kph.
I'm a baloney smoker.
The best I've ever got on the Vancouver Island highway doing a steady 130 kph, is 8 L/100.
I'm more interested in performance than fuel economy. I still only have to fill up once every two weeks.