I need to do my first oil change in my D6-9u (diesel engine that is). S/N 9u59xx. How do I know if I have the "full flow" or "by-pass" system. I don't know what filters to get. I want to get them at the local NAPA store. I asked the counter guy, and he told me to bring in my old filters and he would get the numbers off them. Anyone have the proper # for the filters? Without starting the whole what oil do I use debate, I plan on using straight 30 weight in whatever brand NAPA carries. Any other info. on how to change the oil and filters would be appreciated- such as a step by step "how to". Thanks.

I got SJ's reply over on the other site (thanks) but just wanted to know if there was any other useful info. out there- such as what the differences between "full-flow" and "by-pass" systems were. Thanks.

The full flow should have one big element in it & most the systems were changed over sometime in the life of the tractor & the by-pass had a metal screen element in them with a smaller element inside of it.Cat sold the kit to change the systems over from by-pass to full flow & I always at the shop would put the full flow kit in when one came into the shop to rebuild. The old full flow part number for the filter was 9F 6700 but the Cat part number has been changed over the years a couple times so isn,t up to date now. Just take your old element to NAPA & I,m sure you,ll get the right one.I,m not sure but it seems one of the later full flow elements was a 5S484 but can,t remember if it was the one for a D6. My parts books & info. is pretty slim on equip.

The Wix (Napa) full flow cartridge is a #51161. About $10.00 ea.
Make sure that 30wt is heavy duty for diesels and not the automotive stuff.