Well, on our beater Saturn we have 160k/21 years on the same tranny oil....I'll never change it...it is a beater...but runs really well and shifts smoothly....so, for me, it is a lifetime fluid
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They are great bumper cars too (wife is a PharmD) and it lives in a parking lot and gets hit all of the time...the plastic panels just pop back out...how do we know when it has been hit....a 20 dollar bill under the wiper (like that is a fair deal aye lol)...so far we are over 300 bucks.