Originally Posted by racin4ds
Originally Posted by dnewton3
A few points for me to make:
1) there are several members here who've run 10w-30 HDEO conventional oil in their 6.0PSD and never had one problem
2) the HEUI system in the 6.0 will prefer a 30 grade. You either feed it one, or it will shear your 40 grade down to a 30 grade soon after the OCI anyway
3) the OPs experience is anecdotal at this point
To really know if you can fairly blame the 30 grade, you'd have to not alter the engine whatsoever, and then do repeated back-to-back testing. You have to turn the input variable (grade) on/off, and see if you can turn the output (perceived poor running) on/off. This typically needs to be done three times with affirmed effect to be considered plausible. So far, we have 1/6th of the experiment done; he's run the 30 grade the first time. You've so far not proven correlation. And without correlation, there can be no causation. I'm not saying he's wrong; I'm saying he's a far cry away from actually proving anything.
Generally, in colder weather, the thinner grades actually help the PSDs run well. I've seen them used in my neighbors 6.0L for several seasons with no ill effects, and we've ran 30 grade in my son's 7.3L PSD will no harm either. And as I said previously, there are some members here who've had great success in terms of both performance and wear control using dino 10w-30 HDEO.
I believe the experience is coincidental at this point.
DNewton- thanks for chiming in. I value your opinion as I do a few others on here. I did not mention in my OP that I have ran 10W30 in this truck before (always rotella) especially when I lived up north in the winters. The truck as always loved the 30WT oil, I only went back to the 15W40 when I moved to Florida and found that the 10W30 was harder to find.
The only variable that has changed this go-round is the use of MotorCraft brand oil. I had a bottle of HotShots Stiction eliminator on the shelf in the garage so I dumped that in last night as It may be purely coincidental at this point since I do have 131k miles on it now and the truck has been flawless. Just last year it pulled a our gooseneck trailer loaded with 3 fat mares and tons of other stuff 22 hours on our move from WV to Florida and averaged 15MPG! My wife easily outran me in the Uhaul with the new Ford V10.
Do you have any wear metal data on 10W30 vs 5W40? What constitutes a truck "loving" or "preferring" an oil?
I do see the technical reason for slightly better fuel economy, but along the same lines a less viscous oil will be more prone to leakage in the high pressure oil system. As far as wear metals, I have seen no indication that there is a statistically valid difference ......... Afterall, if a 6.0L will shear a 40wt to the high end of a 30 wt in 5k miles, so why not keep driving it as a 30 wt for 5k more miles - since a 6.0L is believed to prefer it? Most of the data out there shows that the TBN and TAN are still plenty good.
I have data showing that Rotella oils (whether a 10W30 or a 5W40) will shear a little faster than other brands. That said, I have no reason to prefer one vs another (and I don't). It is just that the data needs to be used instead of blanket statements ... especially by folks that (and rightfully so) are always reminding us to draw conclusions on data and not on gut feel. That said, I too have valued DNewton's posts and opinions., but the 6.0L seems to generate and perpetuate a lot of strong "gut feel" opinions.