I have 145k miles on my '06 S2000 and run it the way it should be ran. High rpm's and I do that in high heat(100F + air temp) I suggest you go to S2ki and look at all the engines that have gone boom.Some go bad at the bearings(spun) some at the pistons(scored cylinder) some just drop a valve for some unknown reason. I run high moly(550+ ppm) with 1200+ ppm ZDDP, and my wear numbers are low for the miles I put on the oil(7000 to 7500 miles)No need to change the oil sooner if its doing its job which is lubricating and protecting from metel to metel contact. At the very least I run Mobil 1 0/40 with a full can of MoS2. For most of the last three years I run 2 qt's of M1 0/50 racing oil(or M1 V-Twin 20/50) and 4 qt's of M1 0/40 with a Baldwin B202 oil filter.
Don't go thin, let the engine warm up(oil temp takes longer to warm than water) before you start to bang on it. Have fun with it because thats what this car is made for.
These engines are very hard to rebuild so take care of the one you have. If you search on S2ki you will find most who try to rebuild their engine, well most don't turn out very good and they have to spend more money on a custom build.
So spend a little extra on a good oil that will let your S live a long life.
I don't know if you can get Lucas Hot Rod & Classic Car Motor Oil SAE 10W-40 but it has a ton of anti-friction agents(moly 900, zinc 2200 phosphorous 2600) If your S uses oil like 1 qt. every 1500 miles the Lucas will kill your cat. converter sooner than a oil with less ZDDP in the oil. But if you don't run a cat this is one oil I'd try.
ROD