I have searched and haven't really found any definite answers, other that people saying both are fine, and dont use one etc lol.

I have an 88 s4 base model. Open diff, so in theory I would use the redline 75W90NS, but I've also read on here that the 75W90 (with additives for LSD) works fine, and may even be better for the open diff?

Just curious if anyone has any concrete answers on it. Thanks!

 

considering the brand of oil isn't going to make it somehow stronger, just use the standard 75W-90.

 

I just happen to be looking at redline so I posted the question for it So the standard 75W-90 with LSD additive is fine to use in an open diff then?

 

LSD additives are fine for open diffs.

 

yes, almost all 75W90 oil is GL5 rated for use in LSDs, doesn't mean it will harm anything in an open diff. it simply has additives that work for clutch and clutchless type differentials.

 

Thanks for the reassurance, even though I don't have a LSD I think i will just go with the regular 75w90 instead of messing with the NS.

 

I have used both and did not notice any difference. I think the NS is intended more for racers with LSDs who want to customize the fluid by adding friction modifiers to their liking.

I also tried several types of transmission fluid, but in this case I do have a preference; Red Line MT-90.