Which is the best viscosity oil?

[JOwen72]

I buy my oil in bulk, so I'd like to get something I can use all year. I already run 15-40 in my farm equipment, can i run that all year or should I buy something else for year round use in my 2013 6.7?

[JOwen72]

Oh and I'm located in the Pacific Northwest. We get cold winters and hot summers. We can get down to -20 in the winter, although we haven't seen much below +20 this winter, and can look forward to a few weeks of almost 100 in the summer.

[JuniorDiesel]

If truly gets that cold I would get the 5w-40 for easier starts.


Sent from AutoGuide.com App

[fosterelli]

If I still lived in Oregon I'd be running 5-40...in Texas I run 15-50. Remember, the winter rating is the low number...in cold climates I always choose the lowest winter rating my engine manufacturer allows.

[TRENT310]

I used 15W40 CJ-4 for a little while because as you said it was conveniently available and usable with many other pieces of equipment, but then switched back to 5W40. It does make a bit of a difference with cold starts.

I guess the train of thought is that the cold weight is the lowest it will shear down to when the additives to make it 40-weight wear out, so the 15W40 will only go down to a 15-weight while the 5W40 could go down to 5-weight, but then again this isn't a 6.0L and we're not extending oil change intervals.

[JOwen72]

It's plugged in 99% of the time during the winter, and it's always garaged so it's usually warmer in the garage than it is outside. I'm running Schaeffer's oil, I don't know if it's okay to extend oil change intervals with a semi-synthetic or not?

[roadrunner]

I still own a 6.0, but I thought the 6.7 speced 10w-30? I've used 10w-30 for years and over 100,000mi. in my 6.0 and also the IDI 7.3 with great UOA's.

[JOwen72]

My last pickup was a 6.0, I had it for five years and all I ever put in it was 15-40. There was only one time it didn't start, but it was -15 and had been sitting for 3 days.

[fosterelli]

Originally Posted by JOwen72

It's plugged in 99% of the time during the winter, and it's always garaged so it's usually warmer in the garage than it is outside. I'm running Schaeffer's oil, I don't know if it's okay to extend oil change intervals with a semi-synthetic or not?

From what I hear, extending OCIs is not really feasible without tuning/deleting, due to fuel contamination in your oil from your smog crap. If you're tuned/deleted, I believe your UOAs will prove extending is okay.

[sobiloff]

Originally Posted by fosterelli

From what I hear, extending OCIs is not really feasible without tuning/deleting, due to fuel contamination in your oil from your smog crap. If you're tuned/deleted, I believe your UOAs will prove extending is okay.

Yep, definitely need to be careful going for extended oil change intervals because of all the new emissions stuff, especially if you're going to use any B20.

To the original poster, JOwen72: 10W-30 will do you fine down to 0 degrees F, but if you have to run in lower temps then 5W-40, 0W-40, or 0W-30 are your options per the owner's manual. None of them have an upper temperature limit. (15W-40 is only recommended down to 20 degrees F.)