Are synthetic oils a no-no for wheeling in water?

[ld50]

A rear end specialist told me that synthetic oils don`t protect as well as 90 weight oil in your diffs if you get any water in there.
He said if I want to change the oil every time I go through deep water, or sit for a few minutes in over-the-hub water or mud, then go for it. He said 90 weight can handle some moisture better.

Since I work in the oil industry I can vouch that oil can absorb and contain a certain degree of moisture content within it. Some crudes, as much as 1% and up.
I don`t know much about synthetic though. Could it not mix or absorb it, thereby causing rust in the vitals?

I stuck with the 90 weight just so I don`t have that statement eating away at me every time I drive through a stream.

Whaddya know about this?

 

[mattadams]

first off, why are you getting water in your axles anyway? The front has a breather tube and I don't even worry about the back, so unless you get one of them several feet underwater (in which case I'd be changing the diff fluid whether it was synthetic OR conventional...) then you really don't have to worry abotu water getting in..

 

[ld50]

Yeah they both have breather tubes, the back one is real long and high and I still want to extend the front one to be sure.
I wondered that water could get in there another way. Seals are great for keeping oil in, which is thicker. What about keeping water out if you sit submerged for a while?
-Seems to me that the water repelling quality of the oil would help keep it out too, so I don`t know, seems like a stretch.

Maybe the "expert" just wants to validify his not having any synthetic oil on hand by slandering the product?

 

[Jason_25]

You shouldn't need to worry about the water reacting with the oil. It should never get that far. Extend your vent tubes (yes, even the rear one) into your engine bay or even better, into the passenger compartment.

 

[yob_yeknom]

Plus, if you get water in your diffs, you're gonna have to change the oil in them anyways. So it really doesn't matter if one oil absorbs a little water or not, it's gotta be changed regardless.