i know the manual says 15k or 30k but is it necessary to change it after break-in period? i just passed 5000 mile mark and wondering if i need to do those or not.

 

I change tranny/differential once every 15,000 miles or so.

 

Change it NOW. Then every year or every 15K miles.

 

^ what he said.

 

LE-607 is a good choice for diff fluid. Several vendors on s2ki sell it.

 

Does it say in the owner's manual to change the differential/tranny fluid after the break in period?

 

This is the result of Redline 75W90 Diff Oil after 15,000 miles.



Note the first sentence on the comments (click for larger image).

 

No, it doesn't. I'm only going to talk about the diff fluid here. This is one area in our owner's manual that I and many others believe Honda is very remiss with their information. We have a very small rear diff and a very low volume of diff fluid for the kind of power that is put through there. Also, in many cases, we see a tremendous amount of abuse in the way that this car is driven.
The diff fluid is one of the few aspects of the overall reliability of the rear diff that the owner can take responsibility to ensure. It has been seen time and time again that after the first few thousand miles of an S2000's life, that fluid has undergone the most amount of duty that any load of fluid will see in that amount of miles. It is also this time that we see the most amount of collected sludge and other metallic materials stuck to the magnet. Diff lubricants protect by its physical slipperyness, the chemicals in its make up and by drawing heat away from the metal and transferring it out of the diff. Changing it early and then once every 10K to 15K miles is not so much to ask of its owner since the owner asks so much of it.
Of course, if your driving situation is unique, you may be able to get away with adhering to the "book", but then, how do you know if your driving style is the style that such driveline components really have a hard time dealing with? In the end, it's up to you, the owner as to what you wish to do.

 

Thanks for answering my question