First off, do you have a manual or automatic transmission? If you have a manual, any manual transmission oil will work, since it is nothing more than a bunch of gears with no fluid pressure or combustion heat. If you have an automatic, used only what is recomended in your manual. Not all ATF is the same, and you can do serious damage if you don't use the exact recomendation from Honda. Second, a little smoke comming from the oil fill cap is normal if the engine has been running a while. Any car will do this. That's what happens when oil gets hot. As for which type of oil to use, I would not go any heavier than 10w-30. If your car recomends 5w-30, I'd use that. The number with the "w" is the thickness of the oil when cold, so the lower the number, the thinner the oil when cold and the faster it will circulate thought your engine when it is started cold. The number after the dash is the viscosity when hot. Using anything above 30 is usually for racing or high compression engines only (like diesels). You don't want to use 40 weight if you're not running at 6000 rpm for 3 hours straight, because it may be too thick to circulate properly through a normal running engine.