I've only ever heard good things about amsoil but never tried it, run mobil 1 mostly.
When we had the dry clean delivery vehicles we would put close to 50k per year on them.
I got tired of getting the oil changed on them all the time. First I went to am soil but the rep was too slow so I switched to Mobil 1.
I ended up changing brakes and oil on them between 10 and 20k miles. Except for the dodge caravans that only got 10k on sets of brakes!
Never had any problems with them at all.
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