Any truth to the idea that a 5.9 L cummings diesel needs rebuilt around the 10,000 hour mark?? So are hours just as important as mileage??? Thoughts, comments???

 

A lot of diesel engines are used in vehicles and applications that don't travel many miles. Some things - like generaters and water pumps - don't travel any miles. And some people will have the engine at an idle for hours at a time. For those applications, hours are a better judge of use.

10,000 hours of highway driving would be 700K miles.

 

Well 10,000 hours might not be 700k miles for most 3rd gen owners. Somewhere between 300,000 and 500,000 might be more realistic. But that said if you have 10,000 hours and engine is still performing well then Uh...

 

IIRC, the 10k hours is at full duty cycle constantly so that is a bit of a difference between what our trucks see.

The steps to check for a rebuild are the same until it fails minimums; compression, bleed down, and oil pressure. If they are within spec its good to go until they aren't.

The ISB 5.9 is advertised as around a 700-750k engine in normal circumstances. YMMV.

 

If you averaged 35mph for 10,000 hours that would put you right at the rated engine life of 350,000 miles. I remember some engine hour threads on DTR where average speeds were close to that for a daily driver. That being said, there are numerous 5.9 Cummins engines that have gone 500,000-1,000,000 miles.

 

I remember reading in a Dodge provided "daily log/hours book" stated 1500 operating hours equaled 50000 miles. If one was to use 10000 hours equaled 700000 miles would average 70 mph, an impossibility! The big truck I currently drive has 256000 miles with 5500 operating hours on it!

 

With 170k miles I am at 4100-hours. 10k hours sounds like 350-400k, or, maybe just above the average speed seen by most owners. The best service life will be seen by those with above 35-mph, the worst at 25 mph or less. (Same for fuel economy: work for one and you also receive the other).

 

I do 99% local driving stop and go..... At 70,000 Miles I have 3600 hours.

 

The 10k is for average road speed at 75 mph, or, 750,000 miles. Thats the published number. At 35 mph you are the severe duty category and expected life is reduced by almost halh, around 400k. It will somewhat depend on maintenance of course but the lower speeds and too much idling will reduce life expectancy.

Yikes!! Thats 19.4 mph average, not what you want to do with a Cummins.

 

my semi has 575K on it and only 16000 engine hrs, and she dont use a drop of oil till i get about 9k on an oil change. I'm hoping to see 30000hrs before she takes the big sleep. I dont know how long a well maintained C-12 will last though.

 

I use my mileage spreadsheet to calculate average tank mileage as well as total average mileage. Overall I'm averaging about 38 MPH. Pretty good knowing that a high average MPH is good for long life!

 

Maybe thats why It needs a new injector or 2 every 20,000 miles... who knows.

This truck is used in my business for heaving pulling. Couldnt quite pull this much weight with a gas engine.

 

Mine will probably live for ever. It has an average around 54 mph.