Jake,
Your engine is designed to run with 30 wt. oil at 180° or thereabout. You know how thin that oil seems to be when you get it hot and pull the drain plug. It seems thin, but that's just right for the engine.
When you start, whether the outside air (and the cold oil) is 40° or higher, the oil is much thicker. Put a bottle of straight 30 wt. in your refrigerator, chill it to 40°, and pour some out. It's thick. When it's this thick it isn't lubricating your engine as well as when it's completely warm.
You didn't tell us what engine you have, so I'll assume that the owner's manual calls for an oil that's 30 wt. when hot. If it calls for something different, fill in the correct numbers.
A multigrade oil, 10W-30 or 15W-40, will flow much better when cool and lubricate your engine better. 15W-40 is usually sold for diesels, but if it's marked "API Service Category SJ (or SL)," it's also suitable for gasoline engines. Either of these will be better for your engine before it's warmed than that 30 WT. Also, don't warm your engine by idling; it really sludges things up. Use 10W-30 oil and begin driving gently as soon as the engine starts. Your engine will thank you.
By the way, don't use cheap oil filters. The filter you buy for $2 or $3 is junk, just as one would expect. Even the higher priced version of the $3 filter in the orange box is generally regarded as junk.
Ken
[ August 17, 2002, 11:05 PM: Message edited by: Ken ]