cheers for the response, I have done a little bit more research and found that using the SAF-XA would require 100ml Sturaco additive. Also have found that Shell LS90 has been recommended. I found this info in this thread http://www.fordxr6turbo.com/forum/index.ph...topic=10696&hl= Shell themselves recommend a synthetic diff oil with an additive, what I would like to know is what would be best if I was to use the car for track days, would the mineral LS90 provide enough protection with heat generated or better to go synthetic with additives? This is for a mk 1 sedan with IRS diff