I'd dump a quart in if I can catch it shortly before an oil change. I just have to catch it at right time. Fleet guy probably won't do it. IDC, I will. I haven't seen what filters they use, but I'm betting el cheapo.
I remember as a kid, my dad pouring small amounts of ATF down carb of slant six, keeping idle up, and telling me it cleaned valves IIRC.
Brings back memories. As a kid I worked at an gas station where we serviced vehicles regularly. The owner had mix in a oil can of marvel 50% gas 25% and Diesel 25%, or thereabout by eyeball. He had a quart or so mixed up all the time. On crappy running cars we'd put some in a half pint or so plastic bottle with a hole drilled in the cap and squirt that down carb of a running engine about 2,500 rpm "to free up the rings" couldn't do it too fast or engine would stall. Thing was it made plumes of smoke. He had me always call the fire dept before doing a car as there was a lady on the back street that would sometimes call in a fire at the gas station. Poor old lady feared that someday the block would burn down because of the gasoline tanks (underground)..
