Truck "Making" Oil

[BigPapa]

Our buses weigh 20K-25K empty, 25K-30K loaded. Except for idling, our 6.7’s are constantly working as hard as your truck pulling your 5th wheel.

 

[Timd32]

Thanks for the update.

 

[Pizzamaker991]

Stop thinking about rich so much, it's not a gas engine. Your mechanic really shouldn't have talked about it like that. Cummins likely tuned the engine to run as clean as possible to reduce soot/PM loading, not plug the DPF faster.

Light load driving = low EGT's, this reduces passive regeneration in the DPF. This means that soot/PM is accumulated in the DPF and must be cleaned with an active regeneration, either every 24 hours or when the soot loading reaches ~45%. As soot is accumulated and burned a very small portion of it turns to ash.

High load driving = higher EGT's. Higher EGT's means more passive regen, but you still get small amount of ash built up. You still get the 24 hour regen even if passive regen keeps the DPF clean.

It's possible the engine also is making more soot at high loads than with a light load. I'd be really curios see how clean a 100% stock with delete tune runs at different loads. You don't see it on the DPF gauge because passive regen keeps the DPF clean.


For your sake I really hope you just had a bad DPF, but a plugged DPF from ash buildup in 35K miles isn't normal (unless the wrong oil spec was used, or the truck is consuming oil). Light driving means you've averaged less fuel burned, so you should have less total soot/PM accumulation over someone who has burned twice the fuel you have in the same number of miles. It's the cleaning of the DPF that leaves the ash deposit, regardless of an active or passive regen. Active regens do get the DPF cleaner than passive regens due to the increased temperature, which is why there is a 24 hour regen max interval.

Thanks for the clarification, ultimately because I don't use the truck that hard (90% of my driving is to work and back) I can expect this to happen again probably around 65-70k. At that point I will decide if the truck gets deleted or traded in.

Our buses weigh 20K-25K empty, 25K-30K loaded. Except for idling, our 6.7’s are constantly working as hard as your truck pulling your 5th wheel.

I don't know where you are located but in my area alot of the schools and bus companies have switched back to busses with gasoline (or propane) engines because of the problems. From mid Nov through mid March the busses generally idle from 5:30am until pickups start around 7, then from 1:30p until schools dismiss at 2:30p every day. So 3-4 hours idling every day, and it was killing the emissions systems.

 

[BigPapa]

I’m in TN. My point was, we’ve not had that many DPF issues because they’re worked harder. The drivers aren’t allowed to idle for extended periods. All that is inspected at regular service intervals. I don’t know of any school system’s moving from diesel to gas or propane.

 

[Diesel85]

I’m in TN. My point was, we’ve not had that many DPF issues because they’re worked harder. The drivers aren’t allowed to idle for extended periods. All that is inspected at regular service intervals. I don’t know of any school system’s moving from diesel to gas or propane.

My area school system is moving from diesel to all electric by the end of this Fall. A school system in the next county dropped all their diesels and went to propane with Power Solutions International engines.

I really miss the old DT444E and DT466 engines in school busses.

 

[Ozymandias]

To much money in this country that they can swap whole fleets at a time.

 

[Diesel85]

To much money in this country that they can swap whole fleets at a time.

Right?

They didn't even do a vote on it either. The community had no say in the matter at all. They just do as they please without consideration.

A lot of parents (including the local volunteer FD) are worried about battery fires and that they just don't want it.

My school taxes are going up for sure next year.

 

[BigPapa]

How many buses in those fleets?

We have 15 electric buses ordered. Our fleet manager said the day they’re delivered is the day he’s retiring. There will have to be a complete facility installed and a mini substation built just for charging. No telling what that will cost. We have three propane buses now. There’s one place in town besides our shop to fill them. No way we could switch 600 buses to propane.

 

[Cummins12V98]

To much money in this country that they can swap whole fleets at a time.

Hey “FEELING” good is priceless!!!

 

[Diesel85]

How many buses in those fleets?

We have 15 electric buses ordered. Our fleet manager said the day they’re delivered is the day he’s retiring. There will have to be a complete facility installed and a mini substation built just for charging. No telling what that will cost. We have three propane buses now. There’s one place in town besides our shop to fill them. No way we could switch 600 buses to propane.

The electric fleet is around 75 buses. That also includes a new charging facility and garage. << Which again, typically structures and major capital expenses we usually vote on. They could only keep it down low before the locals found out.

Last year the county next door ditched 250+ diesel buses for those LP busses. IIRC, they did buy some gas buses with the same engine too.

In all fairness though, LP is about $2.49/gal versus diesel being $4.30/gal. Almost half price, but I'm sure the MPG numbers are horrific with LP. So is there really any savings?!

 

[Pizzamaker991]

It has been a little over six months, so I figured a long term update was in order.

The issue with the frequent regens did indeed come back just as AH64ID predicted it would. All was great for a couple thousand miles then like clockwork it started to regen every 100-150 miles again. Coming into winter I figured let it go until spring and deal with it after plowing season.

Once temps started getting sub 45 I noticed that the truck just didn't seem to have the heat that it should even after driving 30+ minutes. As luck would have it I spotted another topic here asking about the normal running temps for these engines. I never really thought anything of it, but for more than the last year this thing never got to 190 even towing and if it did, as soon as the engine load was reduced it dropped back to what I thought was normal 168.

I discussed this with the truck shop that did all the emissions work, and they agreed that I likely had a bad thermostat. I ordered a new 190 cummins stat from Geno's and swapped it out. After the replacement, driving for as little a 5-10 minutes it is right up to 190ish. Over the course of the next couple regen cycles they began to go longer and longer in between. Now they are back to what I always considered normal for my type of use and driving, some have even gone to the full 24 hour interval.

So to sum it up; thousands of dollars in parts, hundreds of dollars in unnecessary oil changes, more dealer visits than I can count, and some new grey hair......a $52 thermostat was all that was wrong, and no one could figure it out.....

So as it is, I am assuming running to cold causing excess soot and poor fuel burn was the issue this whole time.

 

[Timd32]

It has been a little over six months, so I figured a long term update was in order.

The issue with the frequent regens did indeed come back just as AH64ID predicted it would. All was great for a couple thousand miles then like clockwork it started to regen every 100-150 miles again. Coming into winter I figured let it go until spring and deal with it after plowing season.

Once temps started getting sub 45 I noticed that the truck just didn't seem to have the heat that it should even after driving 30+ minutes. As luck would have it I spotted another topic here asking about the normal running temps for these engines. I never really thought anything of it, but for more than the last year this thing never got to 190 even towing and if it did, as soon as the engine load was reduced it dropped back to what I thought was normal 168.

I discussed this with the truck shop that did all the emissions work, and they agreed that I likely had a bad thermostat. I ordered a new 190 cummins stat from Geno's and swapped it out. After the replacement, driving for as little a 5-10 minutes it is right up to 190ish. Over the course of the next couple regen cycles they began to go longer and longer in between. Now they are back to what I always considered normal for my type of use and driving, some have even gone to the full 24 hour interval.

So to sum it up; thousands of dollars in parts, hundreds of dollars in unnecessary oil changes, more dealer visits than I can count, and some new grey hair......a $52 thermostat was all that was wrong, and no one could figure it out.....

So as it is, I am assuming running to cold causing excess soot and poor fuel burn was the issue this whole time.

Thanks for the update.