I go every 2 weeks unless I have a clean out , I use the light Iron to buy me a coffee and 20 bucks worth of gas , I sell everything as needed to make a 100 dollar trip which I have only failed once this year because the Auto place told me the tranny was drained along with an engine , when I flipped the tranny over to put in the dirty aluminum Pile fluid started leaking !! I was not allowed to dump it same with the motor , walked away after 90 minutes helping to clean up the spill with 18 bucks , luckily the guys there like me and my dogs !!