Hydraulic fluid replacement dextron III or synthetic

[Gregory J Dugre]

Owner manual calls for Dextron III but others have told me to go synthetic it's better. I'm concerned because when I drain the system. All the Dextron won't come out and I'll have a mixture of both. The system only runs the power steering and the radiator fan and I think the only danger will be to the seals. Don't want to have any leaks or pump problems. Any advice would be appreciated.
Thanks Greg

[Steve Huber Co-Admin]

Not clear why you would want to change from the OEM recommended if you are going to change it per the manual's recommendation.
Steve

[Eric Maclean]

Greg
If you are talking the difference between dexron 3 and Alisons Synd trans the Syntrans has a longer recommended change frequency but that's only in an Alison automatic transmission.
The Dexron 3 is already a synthetic hydralic transmission fluid maybe without some of the special friction additive packages of the Syn trans  but it was also go enough that Alison ran it for years in there transmissions before the switch to Syd trans.

IMHO it would not be of any advantage to up grade to Synd trans in your hydralic power steering and fan pumps
The Dexron is already a synthetic and the almost double cost of the Synd trans would not be worth the expensive as the friction additive packages are irrelevant in you hydralic system .
There fore I with Steve on this one I'd just stay with the factory recommend fluid and change schedule.

Hope this helps
Eric