jdm civic- 5w-20 is a motor oil honda has been using in it's new cars since the new civic came out. it's mainly for emissions and gas mileage. supposedly honda says the tolerances in the newer motors are so close that a thin oil is necessary.

anyways, i have yet to here of a synthetic 5w-20. i have been using the honda stuff in my girls 02 civic. i plan on using it till 36k, for warrantee sake. i asked this question at po.com and a honda mechanic reccomended i think it was the mobil 1 0w-30.