Today I’d like to talk to you about oil in these trucks. There is a lot of talk on the internet about extending oil change intervals. That is not really a good idea – especially in a 6.4L. I have seen a lot of oil related failures because people extended the oil change interval. If you do, with a functioning DPF, it is very common to get a lot of fuel in your oil which will break down the oil and destroy its ability to lubricate. Modern oils have gotten significantly better over the years but they are still not perfect.

The federal government mandated better and more stable oil because oil burning was causing DPFs to clog. Diesels by their very nature use some oil. So, by making oil more stable it didn’t burn as much. Oils are much better, but you still have to change it or you are going to end up with problems like this.

This particular truck is typical of some of the things that we see in a 250,000 mile truck. Supposedly (I don’t believe it) it was using Royal Purple at 20,000-25,000 mile oil change intervals. Let’s take a look at what happened…

When we pulled the valve cover off, we can see a significant amount of coking. Royal Purple should have never done this. The better oils, like Rotella T6 and others should never have done this. This is like a Pennsylvania-grade, Pennzoil, Quaker State looking stuff. If we look down under the valve cover, it is just a nasty, grimy, gooey mess. The oil has actually gone back to its original form which is coal. You are literally creating coal underneath the valve cover. When you look at the rocker bridges, there is extreme wear. This guy swears up and down that he used Royal Purple. I think whoever was suppose to be putting the Royal Purple in there, didn’t actually do it.

This customer came in with a dead cylinder and wanted the one pair of rocker arms replaced. I wouldn’t want to be the one that ends up with this truck. It is just a matter of time, before the other worn rocker arms fail or something else is going to fail. I can’t imagine what the valve guides look like in this engine.

The moral of the story is: change your oil. I don’t care what kind oil you are using; it is a good idea to change it at 5,000 miles. If you are just using it around town, not running it hard and not pulling heavy, 7,500 is possible. But 20,000 mile intervals – come on. It just doesn’t make sense.

250,000 miles is a lot of miles. Who knows how much idle time is on this truck on the job site. How much can you really complain? However, if he used good oil and actually had it changed on correct intervals, this engine might have had another 50-100K miles. At this point, he will probably have to trade it in or look for chronic problems from now on. ~Bill Hewitt

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