automatic transmission My service manual states that the fluid to use is Dexron 11 .My local garage mechanic used ATF 111 is this ok?
If you are saying that they used Dexron III instead of Dexron II, that is completely okay. They are not interchangeable, since Dexron II should not be used in a transmission that calls for Dexron III or something higher. Dexron III exceeds the properties of Dexron II.
In fact, the original GM ATFs have been superseded by Dexron III.