So have either of you considered a synthetic like, Mobil1 0W-20? I haven't yet as both my mechanic and the Honda dealer say it won't make a difference or it's too expensive. But I see many hypermilers insist on it being one of their adjustments for increasing mpgs.
Also, what do you use to get under your car to get to the filter and plug? Or how to you do it yourself?

Roland

Green Car: Not to exceed 55 miles per hour.