Peterbilt 2010 387 model Burning oil Cummins isx

My '06 starts burning oil at 13k. It needs 1 gallon like clock work. Then another gallon in a week if it doesn't get changed. It knows when the oil change is due

 

definitely no. I do not add any oil, though level drops from Top mark to 1/4 above Low mark.

05 ISX 400, 1,150k miles

 

normal? not really, but it's not necessarily bad. just a sign of mileage catching up. check your blow by. if blowby is exceptionally bad better start planning for a rebuild. if blowby isn't that bad, try changing oil brands. also how long have you had this truck? if not long, it's possible you are running it different than the previous owner. diesel engines are cantankerous grouchy old men. they get stuck in the habit of doing things a certain way and don't like changes. if it is used to running at 1650 rpm and you run at 1250 that could explain the extra oil consumption.

 

it is better to run at lower rpm. however engines get in a pattern. they don't like changes. to be honest I don't really understand why, but it's been true on every has our diesel engine I've ever owned. play around with what rpm you run in and you may find your oil consumption goes down. but even if it does, id rather burn a lull oil at 1250 than burn a lot of fuel at 1650. I still recommend the blow by test. if your rings are worn you will have a good amount of blowby

 

Asking that question will likely cause a heated discussion because there are so many opinions on it. Personally, I try to look at this type of question with the consideration of what science might be behind it. That being considered, I do know that the CM871 seems to be designed for maximum fuel mileage around the 1000-1500 rpm range. This is the range where there are the LEAST air and exhaust restrictions. Above 1400-1500, the higher air flow into and out of the engine starts to become more restrictive. This can be seen by monitoring the rise in the exhaust back-pressure sensor, when comparing it to RPM. They seem be fairly close in rate of change percentage wise, but the back-pressure starts climbing faster than RPM above about 1450 or so RPM. This fact alone, most of the time would dictate that the engine would be more efficient at the lower 1250-1350 rpm range, but there are more than just air-flow factors at play when figuring out fuel economy vs RPM. The truck itself, how its geared, and the speeds you drive will far outweigh slight differences in air flow to/from the engine. Because of this, you must first figure out what gearing the truck has to determine what speed the truck was geared to run. Aerodynamics, rolling resistance, speed, etc. etc.etc. the list is long, will determine the bulk of the equasion, but if your wondering about RPM alone, setting everything else aside, then YES, 1250-1350 is definitely better for fuel economy.

The difference between an ISX engine running 1600+RPM for many hundreds of thousands of miles vs an engine running 1250-1300 RPM for those same hundreds of thousands of miles is generally that the 'Bottom End' will take a more severe beating over time. This generally equates to the rods and mains wearing out faster, and its not unheard of for an ISX running high RPM's for say 600-800k miles to spin a bearing and/or throw a rod because the bottom end has worn down. It has been said also that this same bottom end wear is also the cause of premature piston sleeve wear, but who knows. Keeping that in mind, if I owned an ISX and had to turn 1600+ on it all day, every day, then I would definately have the 'bottom end' done at about 650k miles (vs 850-900k miles) just to be safe. The N14 was more notorious for this behaviour than the ISX as well. Cummins improved the bottom end on the ISX to help fix this problem.

maybe some others can chime in here that have actually had bottom end problems due to high RPM's (stock engines only).