X15 Oil Fuel Dilution

[Hunter013]

I have 2 trucks with identical motors that around 400 hours they start to get low oil pressure. We change the oil and it runs fine for another 400 hours. We've been sending on oil samples since the issues started and it took about 3 samples before they found fuel diluting the oil. What should be the first things I look for? Injector o-rings or injectors? Trucks run well otherwise.

Attached is the sample report. I use Caterpillar sample system because they give it to use free when we buy equipment.

[hookliftpete]

OEM oil filters or third party filters?

[Hunter013]

(09-25-2026 )hookliftpete Wrote:  OEM oil filters or third party filters?

We run Donaldson on our whole fleet

[mikkhh]

Factory programming?

What oil are you using?

[tree98]

Will they pass an injector leakdown test using the insite program? Are they demandated?

[Rawze]

First of all the oil samples that you posted are pretty much useless for the most part. They have no perspective on mileage/run hours between samples on the oil at the time of each sampling.

As far as oil in the fuel, that is usually injector o-ring issues or leaky injectors for an ISX.

Start with doing a proper injector leak tests on it and go from there...
info: https://rawze.com/forums/showthread.php?...3#pid75483

[Hunter013]

(09-26-2026 )Rawze Wrote:  First of all the oil samples that you posted are pretty much useless for the most part. They have no perspective on mileage/run hours between samples on the oil at the time of each sampling.

As far as oil in the fuel, that is usually injector o-ring issues or leaky injectors for an ISX.

Start with doing a proper injector leak tests on it and go from there...
info: https://rawze.com/forums/showthread.php?...3#pid75483

Does the injector leak test run the same on an X15?

[tree98]

Yes it's the same

[Hunter013]

My rail pressure got up to 29,000psi and did not leak down at all even after 10 minutes. What would be the next steps?