What Enables Such Long Intervals With Diesels??

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I just read where a trucking company with the help of Mobil and Cummings have gone to a 60K mile OCI and keeps the engine in warranty as long as they do oil analysis every 10K.
Is it the fact that the 'Big Trucks" have 20-40 gallon oil capacity and the fact that diesel fuel itself is oily that allows such long intervals whereas, gas engines have much lower oil capacity and the fuel itself isn't "oily"?
I have never seen a semi engine with much over 13 gallons in the KTA 450/ 600 hp Cummins engines . Those were nice engines.
 
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Jul 12, 2012
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The KTAs had really wonderful power . Been 25 years since I drove a big truck, I liked driving semis for some strange reason.
 
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Jul 11, 2014
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Proper oil management.... don't need to manage my 5-7 quart sumps... cheap and easy to change oil twice a year on all my vehicles.

Now, if I had to change out 45 quarts of oil, and those expensive filters.... Glad I don't daily commute in an X15 powered economy car.

Now I just need to figure out how to mount that 40 quart sump onto the 2.5 Camry.
 
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Heck, the 3.3L turbo diesel in my Kubota M7060 takes a whole 12.7 qts (12 L) of engine oil. The 3.5L gasser in my Tacoma takes less than half that, 6.2 qts (5.9 L). The oil filter on the tractor is easily twice as large too.

Kubota recommends 500 hour oil/filter changes. That's about 30k highway miles. Toyota recommends 10k miles.

Just thought it was a interesting and relevant comparison. The longer diesel drain intervals seem to hold true with medium-sized engines too. And it seems to be largely influenced by sump size.
 
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silinlimbo
I just read where a trucking company with the help of Mobil and Cummings have gone to a 60K mile OCI and keeps the engine in warranty as long as they do oil analysis every 10K.
Is it the fact that the 'Big Trucks" have 20-40 gallon oil capacity and the fact that diesel fuel itself is oily that allows such long intervals whereas, gas engines have much lower oil capacity and the fuel itself isn't "oily"?
science and experience getting the most for the money
 
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Jan 1, 2003
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My brother works for Freightliner. He was just telling me (among a few engine horror stories) that some engines are now being designed with (I'll call it) sacrificial oil consumption! The oiling system is designed so a small amount of oil is intentionally injected into the intake manifold while running. There is also a huge "backup" supply of oil onboard. As the oil level is depleted, new oil is added from the reserve.
This way oil changes can be extended for VERY long increments.
I'm not saying that Freightliner uses this engine in their trucks, just that the system is out there for commercial customers. (Amazon?)
 
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down in the park
Heck, the 3.3L turbo diesel in my Kubota M7060 takes a whole 12.7 qts (12 L) of engine oil. The 3.5L gasser in my Tacoma takes less than half that, 6.2 qts (5.9 L). The oil filter on the tractor is easily twice as large too.

Kubota recommends 500 hour oil/filter changes. That's about 30k highway miles. Toyota recommends 10k miles.

Just thought it was a interesting and relevant comparison. The longer diesel drain intervals seem to hold true with medium-sized engines too. And it seems to be largely influenced by sump size.

Mitdsubishi diesel engine OCI went from 15,000 km to 20,000 km a few years ago, at the same time they increased the oil capacity by about 1/3rd aswell.... Filters didn't change.
 
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Apr 24, 2018
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I think the key to the extended mile oil changes are total system capacity and by-pass filters.

Despite the bad wrap diesel fuel is “cleaner” in terms of oil unfriendly contaminants
than gasoline which actually has more components that will acidify the oil.

Diesel running primarily “lean” also does much to not destroy oil as quickly as the oil is less exposed to the fuel and coolant especially combined with the superior pollution controls.
 
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Apr 15, 2010
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Despite the bad wrap diesel fuel is “cleaner” in terms of oil unfriendly contaminants
than gasoline which actually has more components that will acidify the oil.

Diesel running primarily “lean” also does much to not destroy oil as quickly as the oil is less exposed to the fuel and coolant especially combined with the superior pollution controls.
But the soot loading is significantly higher. At least it was before GDI came along.

Don't forget ULSD. Sulpher levels dropped off a cliff circa 2007.
 
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