Isn't the oil cooler itself aluminum?
Seems to me that at *some* point in most of the systems we're talking about here (oil, fuel), you'll have steel-to-aluminum in some fashion or another. E.g., fuel...There's a mix of steel and aluminum parts and fittings. The fuel servo is aluminum, the fittings are what, brass, I think? (Not in the shop at the moment). Steel fittings on steel-braided hose to the pump, which has steel fittings, but what's the pump made of? From there, steel fittings-steel-braid-steel fitting at the firewall, but then Al fittings and AL tube from there, right?
So what's the *general* principle of when it's okay to mate a steel fitting to an Al fitting?