When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Regardless, I'd still use a plain Mercon if available, or at the very least, use a dual rated fluid.
I remember two issues attributed to Mercon V years ago when not only it was not a factory approved and recommended fluid, but it was stronlgly warned against:
a) some seals were incompatible with it
b) caused accelerated wear on clutch material
Did E4ODs got suddenly better overnight? Bloody unlikely. Did they change the formulation of Mercon V? Possible, though I wouldn't bet on that.
Recently rebuilt trannies most likely have parts that are compatible with Mercon V, but I can tell you that I'm not putting Mercon V into mine (190k, never rebuilt) unless I can't get anything else.
If it calls for Mercon R use that. I wouldnt use a dual rated fluid cause Ive heard thats not good for the older E4OD's. YOu cant go wrong if you use what it originally called for.