I've always run Mobil 1 75w90 without any issues. Including with my 4.57's.

 

Exactly, my berlina now has 105k on it i use the LE everytime. Got 2 quarts down in the garage right now. Im also anal and change it out beginning and end of season every year. My diff is extremely quiet.

If you have not tried the LE try it.

IMHO your taking chances with anything else.

 

Is there a DIY on how to do this? I found a few dead end threads...

 

DIY Diff fluid Change


Amsoil Severe Gear 75w 110 is what I use.

 

The manufacturer of the diff has very broad requirements, Honda has stricter requirements. Given my own experience with this diff for decades now in Audis, (and FSAE's history) I would use the very best fluid you can buy that fits the Honda spec for warranty and replace annually if racing and every 20-30k if street driving. I use LE.

 

GL4 for the trans, GL5 for the diff

I used RL MT90 for the trans & Mobile 75w90 LS for the diff

Next time ill try the Honda MTF or Amsoil GL4 in the trans to see if there is a difference.

It really comes to down to personal preference, as with any other car different people will have different results with the same oil. Redline may shift smoother in my trans than in yours, Honda MTF might shift smoother in yours than mine. As long as you use the right spec you're not hurting anything. Just dont use GL5 in the trans (Royal Purple, Mobile 1) or its bye bye sychros.