I just checked my owners manual. For oil type it says is to run 5W-20 (I fucked up and put 10W-30 in on this last change...it idles a little rougher but no difference other than that) and says if I want to use synthetic to make sure it's API certified or something. It "recommends" Honda oil. Yeah, ok, like I'm going to pay synthetic oil prices for dino oil. Give me a break.
Service intervals - 10K miles on oil, 20K miles on filter :wtf: That's for regular dino oil, and it says to change synthetics just as often. I'd run a synthetic 10K miles if I knew it'd be good for 10K miles or more, but I'd change the filter at the same time. I see no point in NOT changing the filter when you change the oil, it kind of defeats the purpose of an oil change, plus even a small filter will hold at least 1/3 quart of oil. That's just mixing the old with the new, and would make more of a difference on a small engine (mine is supposed to take 3.7 quarts of oil).
Maybe I'll make the switch to synthetic in about 4k miles.
On another note, the manual says the OEM plugs are a special "platinum tipped" plug and they don't need to be replaced until 110K miles. I just replaced mine at 31K miles with NGK plugs. The ones that were in there were not NGK nor were they OEM. I did notice a slight improvement in acceleration after the plug change. When you've only got 127hp and 114 lb ft of torque to begin with, you really notice the little things that make improvements.