[scalelover]

Either one will work in forks and this is one of those things that really has no right or wrong answer to it, everyone will have their opinion and stand by what they have always used. Their are some good write ups on several forums I've frequented in the past and most always ended up going round and round with no final answer.

What I can tell you from personal experiences and talks with others is One reason it is not recommended is because the viscosity is very unpredictable compared to fork fluid. Many older bikes recommend using it and I believe it was Honda that recommended using ATF on all their forks in the earlier bikes so you should be ok in that aspect if this was your worry.

Most say that it was recommended because ATF is lightweight and was very accessible at that time, unlike fork fluid which was a bit more costly then and was not as readily available. You also have to figure there were not a lot of additives used in earlier days compared to now, where everything is broken down to molecular levels and modified so there wouldn't have been as many concerns of it harming the internal components of the forks.

If you are going to use ATF and need more than one bottle it is recommended to mix the two together before pouring into the forks to ensure correct side to side viscosity. Unlike fork fluid which will be tested and set for a particular grade, ATF will vary in grade and can have many chemical differences from bottle to bottle as it has cleaners, lubricants, and emulsifiers added to it to maintain internal parts like seals. The best one IMO is mobile 1 synthetic and many riders I know use this in their bikes as well.

Hopefully this doesn't just confuse you more and helps you out in some way!!

--Dan