[svxistentialist]

Originally Posted by Nobody

Hi, I have a dilema. Wanna change my ATF (Valvoline) and thinking to go for fully synthetic Mobile1 SHC. Tranny was rebuild 15k kms, 3 yrs ago. Cooler intalled. Question is what will happen:-). Our market here is not so developed as for servicing AT so can not rely on proffesional flush. I can only drain it and refill. There are too many questions, what will happen mixing existing and fully synthetic, what will happen to sealings, internal and external leaks...
Does any of you tried it?
Thanx for any ideas...
Petr

Petr

If you use good high quality fully synthetic it will not "wear out" and the amount that remains in your transmission will be an OK mix with the new fill.
That is assuming you change the oil at one year intervals.

I'm presuming your question relates to the amount of the old Valvoline that you leave in your transmission when you change over to Mobile 1, and this Valvoline is not fully synthetic?

Even a professional flush will not get all the old oil out of a box. It should not make a lot of difference the small amount of old oil mixing with the new. Make sure the gearbox is plenty hot when you drain it, that will help.

Your best bet for a good clean-out is to fill initially with Mobile 1, and do the first oil change in 6 months. This will leave very little of the Valvoline in the gearbox after the second fill.

Thereafter, you need only change once a year, or less, because the fully synth lasts longer. If you also have fitted the additional cooler, your oil won't be overheating, and changes every year or 18 months would be the correct normal interval in that case.

Joe