Engine oil should not increase. When the dipstick reads higher at the end of a shift than at the start of the month, something is entering the sump that does not belong there, and on a Kobelco the usual something is diesel. The oil looks normal on the stick, smells of fuel, and feels thin between the fingers. Guangzhou Shenyue Machinery Technology Co., Ltd. supplies the injector and fuel-system parts involved, and dilution is one of the few faults that damages an engine while every gauge reads normally.
Why a little diesel matters
Diesel thins the oil and lowers its film strength. A 15W-40 that has taken on a few per cent of fuel behaves like a much lighter oil at operating temperature, so bearing loads rise, cam and follower wear accelerates, and oil pressure at hot idle falls. The oil also carries less soot in suspension and oxidises differently. By the time the level is visibly high, the oil has already stopped doing its job. On a machine that works hard in heat, the first sign is often a hot idle pressure that sits lower than it did last season, long before anyone thinks to look at the dipstick.
Where the diesel gets in
| Evidence | Likely path | Test that confirms it |
|---|---|---|
| Level rises slowly, fuel smell, no external leak | Injector needle or seat passing fuel | Injector leak-off comparison across cylinders |
| Carbon around the injector bore | Copper washer seat leaking combustion gas | Visual check with the cover off |
| Level rises fast after a pump repair | High-pressure pump shaft seal | Fuel pressure decay with the engine off |
| Level rises on machines that idle a lot | Late post-injection during regeneration | Regeneration frequency in the monitor history |
The three tests worth paying for
First, the level trend: measure at the same point, cold, every fifty hours, and write it down. Second, an oil sample with viscosity at 100 degrees Celsius and flash point, which shows dilution before the nose does. Third, injector leak-off, comparing return flow across cylinders; one high reading identifies the cylinder. Fuel pressure decay with the engine off separates a pump seal from an injector. Take the sample warm, record the hours on the label, and keep the report with the service history, because dilution is a trend before it is a number.
What not to do
Do not simply drain a litre and keep working. Dilution is a symptom, and the cause keeps adding fuel. Do not add a thicker oil to compensate; the additive package is not designed for it and the dilution continues. And do not assume a new injector set is needed before the leak-off test, because a sticking SCV or a pump seal produces the same dipstick reading at a fraction of the cost.
The parts involved
On J05E and J08E engines the common repair items are injector cover seals in the VH2368178030 / VHS230741070 family, the SCV valve 0928400742 / VA32G6107020 / VA32G6107080, the SCV suction valve kit 294009-1221 / VHS4226E0061 / VH04226E0041, and the oil filter LC11P00019R100. Injector numbers themselves change with build, so they are quoted against the engine serial, not the machine model.
What to send us
Send the engine model and serial, the machine hours, the oil sample result if you have one, and photographs of the injector bores. We hold three thousand part types on the shelf and over one hundred thousand part numbers available to order through original supply channels, each marked genuine, OEM or aftermarket.
The engine parts range covers injectors, pumps and seals, the low oil pressure guide covers the pressure side of the same fault, and the fuel system and SCV guide covers the supply side. Send samples and photos through the contact page. Engine service data is published by the manufacturer at hino-global.com.
Guangzhou Shenyue Machinery Technology Co., Ltd. is an independent supplier of Kobelco parts, not affiliated with Kobelco Construction Machinery Co., Ltd. Genuine parts are supplied through original channels alongside quality OEM and aftermarket alternatives at distributor-level prices.
Frequently Asked Questions
Why is my engine oil level going up?
Almost always fuel dilution. Diesel passes an injector seat or needle, a high-pressure pump shaft seal, or arrives through late post-injection during regeneration, and it accumulates in the sump. The oil smells of fuel and feels thin. Confirm with an oil sample before buying parts.
How much fuel in the oil is too much?
Any measurable dilution is a warning, and the condemning figure in the oil analysis report is the one to work to. Guangzhou Shenyue Machinery Technology Co., Ltd. treats a rising level plus a fuel smell as a stop-and-diagnose condition, because bearing wear begins before the level looks alarming.
Can I just change the oil and keep running?
Only if you also find the cause. Changing oil removes the symptom and the next few hundred hours add it back. Run the leak-off test across cylinders, check fuel pressure decay with the engine off, and inspect the injector bores for carbon.
Which parts are usually replaced?
Injector cover seals VH2368178030 / VHS230741070, the SCV valve 0928400742 / VA32G6107020 / VA32G6107080, the SCV suction valve kit 294009-1221 / VHS4226E0061 / VH04226E0041, and the oil filter LC11P00019R100. Injectors are quoted by engine serial.