I'm no engineer... but the primary benefit with 10w30 over 5w30 is that 10w30 will flow better at subfreezing temperatures.

I assume that increase in low-temperature flow performance comes at the detriment of overall viscosity and therefore, slightly increased drag / fuel consumption.

Keep in mind we're talking about very slim margins here.
It's not like 5w30 is water and 10w30 is like cement.

And to answer your broad question, I use 5w30 because I never see the subfreezing temperatures where 10w30 provides additional protection.

Also, this isn't new news. The Owner's Manual and HELMS Factory Service Manual both discuss the use of 10w30 in cold climates. :shrug:

 

:werd:

im using 5w30 in my b18c1. heck my brother even used 0w40 mobil 1 in his gsr for a while.

 

The difference between 5w30 and 10w30 is so negligible, it isn't even worth discussing. I have regularly switched between the two and I have seen no difference in performance.

But since you are asking, I am using 5w30 at the moment. h:

 

So where did the oil go?

 

you probably drained it after getting it running, planning to change it. Then you got the s2k and forgot all about it.

 

Just picked up 10w-30...4qts ran me $20.73 and I have 1/2 qt left over from spring. I plan on pulling the plug and seeing if ANY OIL comes out.
1)Fill the girl up with some oil
2)Relocate both slim fans to other side of radiator to make more room (like Daschmoo =) )
3) Fill with radiator fluid
4) Check my spark plug gaps. If I can remember Daschmoo. Gap them to .25?
5) Turn the key and go

OH I CAN HEAR IT NOW...weeedeeedeeee WHOOOOMMMMM

For those of you who are new, this was taken last spring right after I did my custom turbo install
ENJOY
http://wtflip.com/vid/core4/imagepages/image4.html

 

:werd: on the fans.

Gap the plugs to .030". .025" won't hurt, but it puts unnecessary strain on the ignitor if you don't need the gaps that low.

 

Bottle of "heet" to help with your nasty fuel.

 

Well...it started right up...I had about 2qts in there, so I drained it then put 4.5qts of new Mobil 1 10W30 in her. I then moved the fans (which might I add look way better hidden) and filled her up with Radiator fluid. She started right up.

I let her warm up and then took her for a spin. Lets just say at 50-60mph in 2nd the tires were spinning when I hit full boost. HAHA, i started laughing my ass off, I forgot how the turbo feels since I got the S2000.

NEXT QUESTION GENTS: I installed a ACT HDSS clutch and a 8lb Findenza. Before I put the teg away I thought the clutch pedal was great...but when I drove it last night the clutch engauged and dis-engauged at about 90% of its travel. I COULD HAVE SWORN it was the other way around, Before I put it away I thought it was E and dis-E at about 10-15% travel...something wrong?