I Don't Understand This Oil Life Chart

[George7941]

This is from the Cummins Maintenance Manual for a 1999 ISB 5.9 diesel engine.

MPQ , I assume, is miles per quart. The sump is 16 quarts, so 1200 MPQ is 19200 miles, 400 MPQ is 6400 miles. Cummins recommends OCI of 15000 mi/normal service, 9000 mi/severe service. So the OCI falls within the limits given in the chart. Am I reading this chart correctly?

The Km/l figures do not make any sense, I can only assume there was some error.

 

[CT8]

Oil drain interval chart?

 

[WobblyElvis]

It is simply suggesting that the active additives remain stronger in an engine where oil is added within an oil change interval. There are no numbers on either axis of that graph/chart so it's just for general information.

 

[pitzel]

I believe what they're implying is that an engine that consumes the lubricating oil, by leakage perhaps, is one in which the oil lasts a lot longer.

I'd be skeptical, outside of the "leaking" scenario, because an engine that "consumes" more oil is likely to be an engine that is less mechanically sound and is prone to more blowby, than an engine that consumes little oil. Higher levels of blowby being harder on the lubricating oil and its additives than lower levels.

 

[Donald]

Charts can say what they want, but a UOA is the only sure way to know if the oil should be changed

 

[bullwinkle]

ISB engines that were pre-in cylinder DPF & EGR can go a lot farther on oil changes-now that they have the excess fuel & soot to deal with, not so much.

 

[Snagglefoot]

I'll throw this out there. I believe the chart is metric. Km is kilometres. L is liters.
MPQ are units in Magnetic Particle Quantification which measures the integral non-linear response produced by magnetically labeled nanoparticles.

Why the MPQ units are going up with kilometres I'm not sure unless it indicates breaking down the particles.

I'm thinking this is a little more sophisticated than base number.

 

[Rand]

MPQ isnt miles per quart.

 

[Donald]

Originally Posted by bullwinkle
ISB engines that were pre-in cylinder DPF & EGR can go a lot farther on oil changes-now that they have the excess fuel & soot to deal with, not so much.


Not sure I agree. I went two OLM clicks last oil change and will go a little further this time. The UOA after two OLM click was good to continue using the oil. My PSD has all the 2015 emissions stuff intact.

 

[George7941]

It definitely looks like MPQ is not miles per quart. Per is denoted by a / in km/l, so one would think they would go with mi/qt or something similar.

This maintenance manual is not meant for tribologists, it came in the glove box of the truck when we bought it in 1999. It is odd they would include a chart like this in the maintenance manual, with no explanation.