Correct oil to use in 99+2000 7.3 diesels

[fase2000tdi]

Mom has a 2000 Excursion w/ 7.3, dad has a 99 F350 with 7.3

I've seen the "how to change your oil" article in maintainence. They use Rotella T 15w40 regular oil. What I'm wondering is if Rotella T synthetic 5w40 would be ok. My dads injectors (4) are running very badly coked up inside, and they aren't firing at all/well.

Appreciate any advice, and I really need to know if I can run synthetic. I've heard synthetic can prevent this. Thank you!

[bigcountrysg]

You can try to change to 5w40. How ever if your dads truck is running that bad. You may want to look at replacing the injectors. How ever I would trouble shoot it before I declare the injectors. Make sure your Hpop is working properly, cps is functioning properly, idm is working, do an injector buzz test, injector contribution test. check the UVC wiring harness. Check everything fuel filter. That way you know for sure it is the injectors and not something that could be alot cheaper.

Changing the oil may help, but what your discribing sounds more like there is a need of trouble shooting the problem, truck runs rough.

[vitalidle]

I switched over to 5w-40 Rotella this winter and it made a huge difference for me with cold startups, and the truck just seems to run better. Could be just me though!

[bigcountrysg]

Originally Posted by vitalidle

I switched over to 5w-40 Rotella this winter and it made a huge difference for me with cold startups, and the truck just seems to run better. Could be just me though!

I aggree with you in the cold weather the switch would be good. But in the middle of the summer, I would have to think something else is causing the problem.

[fase2000tdi]

Love your sig bigcountrysg... I'm more of a shotgun kinda guy at this point though.. 17/25 my last round of trap shootin. And that was with a $35 bolt action Mausser

[vitalidle]

Originally Posted by bigcountrysg

I aggree with you in the cold weather the switch would be good. But in the middle of the summer, I would have to think something else is causing the problem.

Yeah I wasn't trying to correlate his issues with the oil....rather I was letting him know that the Rotella 5w-40 oil is okay to use

[Lord Tauk]

Status on the oil in the one thats running bad? How long has it been in there? Truck use? etc. etc.

Bump for a tech, my best guess is that whatever oil you'll put in there wont make much of a difference if it's running that bad.

I also agree, 5W40 is fine; it really helps in the winter when it's cold.

[AZSnake98]

i just put 15w40 rotella T in mine.

[Performance Oil Products]

I'm not sure how well it's been taken care of, but I too would check HPOP pressure. Also fuel filter change and some power service in the tank and filter housing will help. Chances that the injectors are coked up are VERY slim.

Coking is more common in turbo oil lines.


You won't really notice the truck running any better on 5-40 except for easier cold starts. The damage is already done also so it won't cure a problem


When you change the filter and drain the bowl. Put the new filter in and fill the bowl with some powerservice or seafoam. Then put the lid on. Add about 20 ounces of Powerservice to a full tank of fuel.

I can tell you you will feel a difference. Next fill up add the rest of the powerservice bottle.

That should get it going good

[1sweet7.3]

I run rotella 15-40 works great for me. I change it every 3000mi. because I blow smoke I worry about contamination of the oil.