Just a little side note that I'm sure you are aware of but not everyone else. If your wife draws on your SS she will not be able to draw on hers at the sametime.
I have some cases of oils bellow for sale.
I mixed these at 50/50 and ran it in my S4 Transaxle for many years with no problem.
$15 a bottle.
I used this in the LS for many years also.
$10 a bottle
$5 a bottle