I'm not a fan of 15W-40 oils, at least not common ones on the shelf. It's easier to meet that grade with cheaper, more volatile, and more shear prone base oils and VIIs. When production cost / profit margins take priority over outright performance, so long as the standard is still met, they welcome the lower production cost of a 15W-40. (at the same retail cost) With a 5W-40, they're forced to use better quality base oils and VIIs to meet that grade. Often times, these better base oils will resist thermal degradation better which allows for longer drain intervals or less breakdown within the same interval. The same can apply to some 0W-40 oils. Granted we're talking about ACEA oils here and not CK-4, but a good example is Mobil 1 FS Euro 0W-40 shearing less than Castrol Edge 5W-40 in KRL. (-10% vs -13%)
That maybe true, but it may not matter in the slightest.
A modern 15w-40 outperforms one from 20 years ago.
So in these cases of low use diesels, which are also often older, the requirement for anything special is just moot. And the need for cold cranking, or flow after long sitting, may or may not be there.
Face it, even the most modern engines aren’t necessarily pushing the envelope on stress on the oil. Some do more than others. But for older and low use/light use engines? Paying a premium for something that the performance attributes aren’t used either strokes your ego or separates a fool and their money.
That doesn’t mean there isn’t a case for premium products. It’s just that there’s at least as massive a case for more standard products providing sufficient performance for the long run.
https://bobistheoilguy.com/forums/threads/rethinking-5w-40-vs-15w-40-for-my-low-use-diesels.346111/
@JHZR2, curious what you ended up doing with your low use diesels?
I have a powerstroke 6.7 on a motorhome chassis, which isn't used daily. It can sit for months at a time (will usually drive them in between uses). Cold weather isn't too big a threat here in East Texas.
I have been using 5w40 synthetic, primarily Delcac (CJ4) and switched to Valvoline Premium Blue 5w40 (after Ford Ck4 drama).
Since day one (2015), I've used 5w40 for the same reason you have vs a 15w40. Better flow between starts hoping to minimize wear on infrequent startups.
Last change I tried Chevron Delo synthetic 15w40 as I got a good deal on it.
Just curious if anything has changed?
For me, I have been using 15w-40 in most of my diesels. I have a stash of Schaeffers 5w-40’that I’ve run in my 1981 240D forever, so I keep running that.
I found that Delo has favorable cold flow characteristics, so I run their 15w-40 in stuff that might get started cold. All those vehicles have block heaters and and it’s temperate enough around here for it to be good enough.
For anything that is not going to see that, and/or is getting baselined or serviced, I’ve used Delvac because it’s cheaper.
All that said, the super tech 15w-40 synthetic seems compelling for the cost so I may look to go to that at some point at least for some vehicles.
It’s all about the temperature-viscosity chart…
