I have a 2011 Ford Focus with 260,000 miles and I always change my fluid every 20,000 miles and it’s due. I always use motorcraft fluid but is it necessary to use that or can a use Castrol equivalent and it shifts as smooth as you would expect it to so should I use Lucas transmission oil in it to?
You can't argue with success. Keep using the Motorcraft fluid.
I put Valvoline full synthetic ATF in my 02 Mustang. You have to make sure it meets the specs listed in your owners manual.
Everything you could possibly want to know, and more.
The short of the long is
There are laws in the USA to prevent mislabeled and misleading labeling of automatic transmission fluid and many other products. That does not stop some producers from pushing the limits of ethical packaging labels. Learn the difference between an officially licensed fluid and one that claims to be "suitable for use" in your vehicle. Learn what to look for when making a decision of which transmission fluid to purchase.
https://www.youtube.com/watch?v=xUFY0L_zFek
I put Valvoline full synthetic ATF in my 02 Mustang. You have to make sure it meets the specs listed in your owners manual.
