Legal disclaimer: watering down road fuel is tax evasion so this info is for off road use only. If DOT dips tank, same charges as running red offroad fuel
You should always run some additive in a db2 and db4 pump, they weren't designed for ULSD and will eat themselves alive. Lots of folks have great luck with tcw3 (marine) 2cycle oil as it is low ash. I run half quart per full tank and half a dose of power service silver bottle in my 6.2s. I recommend not using straight used oil or atf due to the particulate matter unless you filter it.
You have to let the waste oil settle and not use the bottom of the drum. Then filter down to 1 micron, some swear by 5 tho. Helps if you heat it.
There is a great write up in the 6.2/ 6.5 section on dieselplace about this. I've been a member there for around 5 years. I'd link it but unsure if that's against forum policy.
WMO and WVO guys have ran over half WMO thinned with gasoline and the rest diesel. Veggie oil need thinned like this also and will coke the injectors over time and doesn't do well in the cold. Ymmv Goodluck!