Loves really took a dump on SpeedCo.

I worked at a fleet back in 88-91 that did dump the old oil in the tanks at service.
That was fine for the NTC315 PT pump cummins, they would burn any thing.
But when we got the first DD60s in 89 and did that with in 6 to 8 months we had injectors clogged with zinc.
So they started dumping the oil in the bulk tank which cut the amount of oil to fuel very low ratio.
It maybe todays oil has much less zinc than back in the 80's and 90's.