I had the cam issue at almost 900,000 miles on my ISX. There was a little known TSB put out by Cummins that there was a defective batch of rockers that were not allowing proper lube on the cam lobes. True to your point, no real problem showed up in oil samples to show it going on. Only when I had the overhead ran did we catch it. Good thing I did those regularly.

Yeah, each person has to live within their comfort zone. I do seem to think that those that won't even try to go to the OEM recommended drain intervals have paranoia issues they need to come to terms with. Some are still stuck on the 10,000 mile oil change game just like many car owners are still stuck on 3,000 mile oil changes, even thought the manufacturers recommend considerably longer drains. But taking oil drains out beyond OEM recommendations, well, that is something each person needs to figure out how they can deal with it. Oil samples should be done every drain regardless, just so you know how the oil is holding up. There is no one size fits all solution. How the engine is worked, how much fuel it uses, etc all come into play.

Some in the 10,000 mile oil change camp will argue along the lines of frequent oil changes are cheap insurance. Well then, why not change the oil every week if frequent changes are the cat's meow? And if you have to change the oil 12 times in a typical 120,000 mile year, yet I only have to change it 4 times, how cheap is your "frequent changes are cheap insurance" argument? Oh well. Some habits die hard. Some would say it is foolish or downright stupid to take drains out to the level I do...25,000 - 30,000 miles. Well, I have taken a couple engines to over 1 mil with no inframe or other necessary stuff doing that. And all engine manufacturers for the last 10 years have a 25,000 mile drain interval or better. Yes.... even Cat, if you are getting better than 6 mpg and gross weights are 80K or less. Read the maintenance manual.

 

The manual on my '06 specified 15,000 mile changes with mineral (except for Valvoline which Cummins approves for longer drains), so that's what I started with. When I switched to synthetic I moved it out to 18,000 then 20,000. Samples were still good and then I got rid of the EGR so I progressively moved out to the 25-30,000 that I currently use. I'll probably add a bypass filter at some point but I have no real desire to extend the drains because of it. It just seems like money well spent to keep the oil I do run as clean as possible. I hear you on the overheads. I run the overhead at least once a year; not because of performance issues but because I want to keep an eye on those cams.

 

According to my manual, and fuel mileage, i could go to 35,000 give or take a few. But according to the same manual, interval shouldn't exceed 30,000 miles, or 600 hours. I also have a Spinner II, and changing oil every 20,000 miles, which comes to between 400-450 hours. That's the compromise i could live with, and since i'm not running that many miles, and changing oil about 4 time a year i call it a "cheap insurance"

 

Wow. My Cummins ISX manual had an oil change interval of 25,000 miles. Oh well, even if that was a misprint, I had no problem going that long and longer. Oil always held up well. On the bypass issue, I have used them for quite some time. My primary motivation was not to extend the drains out to some wild level. I just wanted better filtration and keep a lot of junk out of the oil that would pass thru full flow filters.

 

I just had my engine in-framed (broken head bolt was causing serious water in oil) and the mechanic said the he's never seen an engine with even close to the miles I have (922k) that was anywhere as clean as mine was. The cam bearings were just barely showing wear on the bottom 30 degrees, and the bottom end looked nearly spotless. He said that had the head bolt not broken (a fluke, as nobody seems to ever heard of such a thing on an ISX), I probably could have went another 300k to 500k miles without an inframe being called for. He said he completely disagrees with my oil change policy, but with the results he's now seen, all he can say is that while he doesn't want to hear what I'm doing, he recommends that I keep doing what I've been doing.

On a side note, I highly recommend the KW Dealership in Wichita. They got me in quickly (bumped me to the head of the line, actually) and kept the bill low. KW in OK City estimated $25k - $27k, my local Cummins dealer said $20k - $24k, and my bill out the door is $18,898. That includes recon head, re-core radiator, a rod, a couple new hoses, new coolant tank, new coolant pipe, fix and rebuild broken engine brake and replace solenoids, fix an AC problem, remove clean and inspect the EGR, replace crank damper, and a few other minor issues. The mechanic, Phil Cummins (yep, his real name) has been turning wrenches almost as long as I've been alive and seems to really know his stuff. He spent over an hour talking with me about my truck and showing things I didn't know. All in all, I'm pretty happy with the treatment I've gotten there. I also rented a tractor from their PAC Lease guy (much cheaper than Penske) to get my load delivered.

 

that is insane. if i had to pay for my inframe at my local cat dealer it would have been $16k. did you get a warranty?

again, i keep my oil every 15k. i run the hell out of my truck. my motor is way too small for what i do. when i spoke to my cat mechanic he said i could be going a bit deeper. why use lucas? i like having the oil psi just a bit higher esp. when i'm working the motor in the heat the oil does thin out a bit.

 

Well , when I got my ISX , it had 565,000 on it. Have 889,000 on it now. Tried Mobil Syn. , Amsoil Syn. , Rotella conventional, finally settled on Rotella T-6. I first used Amsoils bypass filter , have now switched to an Oil Spinner II. Mercy, what a difference that made ! Oil consumption has fallen off quite a bit, but I'm sticking with changing the filter every 15,000 miles, and oil changes every 30,000. I was using Amsoils analysis , but am looking for a better , or cheaper , way to go. My dealership expires next month, and since I don't plan on renewing it , I need another oil analysis lab. Soot levels have been high, even after the EGR Delete , and that's worry some. Engine now uses about a gallon of oil every 12,000 miles , where it was using a Gallon about every 4,000.
Had the overhead run 14 months ago. Mechanic said it didn't really need it. Cam looked good, too.

 

Something that has shown up a little more lately is fuel dilution. Did a batch of reading on this and found out some interesting stuff. There are a number of reports and studies showing that biodiesel is starting to be an issue with fuel dilution. There is always some fuel that gets by the rings. Normally, number 2 will vaporize out of the oil and just go on out of the PCV or blow by tube. Well, bio has a higher flash point and vapor point. It is not vaporizing in the same manner as diesel did in the past and is building up in oil and reducing viscosity. Since I run primarily only the upper midwest, there is hardly anywhere that is NOT adding biodiesel to their supplies. So, I for one, am filling with some level of bio virtually all the time. I have noticed an uptick in fuel dilution that corresponds to the 100% usage of biofuels. This has also caught the attention of the oil industry and now they are trying to formulate a new oil classification that will address the problem.

This is especially being noticed in the newer DPF equipped engines, as one method of getting fuel into the exhaust stream to cause the regen burn is to inject fuel late in the firing cycle to increase the level of fuel in the exhaust. This is cheaper than using direct fuel injection into the DPF. This is also causing fuel dilution problems, especially so with biodiesel.

So, if this starts to occur, you can kiss the long oil change interval thing good bye. Yet one more thing to watch out for.

 

Of course I got a warranty. Just the standard Cummins 1 year / 100k mile warranty though. Six and a half years ago I in-framed my 2003 C-15 at Kenworth in Jackson, MS and it cost me almost $17k (with recon head and six injectors). The base quote for this one was $14k, but add in a recon head, new radiator, crank damper, rebuild engine brake, replace some hoses, fix AC problem... little things like that and it starts adding up pretty quickly.

So far, with 30k miles on it, it runs great. I'm seeing mpg way up, especially with lighter loads. Before the in-frame, my highest average tank of fuel was just over 8 mpg, and that was basically deadheading. Since the in-frame, I've had quite a few fill-ups where I was in to the mid 8s and a couple where I broke the 9 mpg mark. It'll be interesting to see where it settles in at once I get the initial overhead done in 20k miles or so.

 

As long as I've been with this company, they've run Rotella in everything. Every Cat C-15 I had would burn one gallon of oil every 15,000 or so miles. My Cummins ISX (2012 with DPF/DEF) does about the same thing. Here I was thinking that this was just normal... Now I have an idea of what to do, if ever I buy that beast.