WD40 
Actually Castrol 10W40 since the truck was new.
Rotella … And to think that I actually put it in a diesel … lol
Pennzoil In the Dakota
Mobel 1 In Jeep
SYN3 In the Harley
Royal Purple Synthetic 10w 40
I use retella in my 7.3 but use castrol in my 6.0 since I was told rotella is the leading cause of injector and turbo failure in the 6.0s
Ive heard that as well about the 6.0 problems … But I dont believe it … Havn’t seen any proof as of why it would cause any failure … But its better to be safe than sorry
well i was told but a diesel mechanic down at the local ford garage that over half the time i truck comes in with turbo or injector problems it was due to them using rotella so id rather not risk it…my dad put rotella in the 7.3 since day one without any problems so who knows
my dad uses this elf 505 spec shit for his diesel u can go like 30k mi between oil changes
best thing for a motor is hydraulic fluid.
RepSol 10-50 in the bike Royal Purple 10-30 in the car
I’m pleased with Super Tech 5w30 synthetic. One of the best oil’s you can use actually and it’s fairly inexpensive.
No way does that outperform vaseline
I know it was already mentioned but I also run Amsoil fully synth. and its a 25K or 1 year interval now (with their filter), I had mine tested about 1/2 through the year which was at the 5500K mile mark and the blackstone lab results came back great with a TBN at 5.1 (active additive) 1.0 is low, told me to check back in another 3K, my year is up in the spring in which I will have upwards of 11-13K miles, I will take a sample on my year end oil change and then pending results, most likely just stick to the 1 year intervals…
They may say 30k between changes … but I would in no way wait that long to change oil … Im a 5k religious oil change guy … Diesels put out way to many composets that break down oil …