Fuel Dilution Of Engine Oil In Plug-in Hybrid *and* Hybrid Tucsons - THERE IS A SEMI-SECRET SOFTWARE UPDATE

A lab test following a recent oil change showed that my engine oil had been diluted over 5% by gasoline. 2.4% is the recommended maximum dilution. In 500 miles of driving since that oil change my oil level had risen to 1/2" over the maximum fill line. Many other owners of Hybrid (HEV) and Plug-in Hybrid (PHEV) Tucsons have been reporting similar dilution of their engine oil. The root cause is increased blow-by of gasoline past the piston rings in TGDI (turbocharged gasoline direct injection) engines and then the oil in these very efficient engines never getting hot enough to "boil" off the gasoline. Dilution of the engine oil by gasoline can cause excessive engine wear. (Other brands of automobiles with TGDI engines have reported similar issues.)

The Service Manager at the dealer where I have my Tucson serviced was totally non-responsive, so I had to raise a bit of a ruckus with some 1-star reviews on social media. Once I engaged with the General Manager, things moved very quickly.

When the General Manager spoke with a Hyundai Regional Field Service Engineer he was informed that there was, in fact, a Technical Service Bulletin (TSB) to address the issue of fuel dilution of engine oil in Tucson HEVs and PHEVs. Apparently the Service Department at the dealer was unaware of this TSB.

The TSB Number is 23-EE-002H. It was issued in March, 2023. (With problems of this nature it can often take several tries to fix or mitigate the problem. Be sure to check for updated or superseding TSBs. The General Manager at the dealer said that he would be checking with Hyundai every month or two on my behalf.)

Most of the TSB deals with DTC error codes being issued erroneously. These error codes have nothing to do with the oil dilution issue. At the bottom of the TSB, almost as an afterthought, there is:


On the TSB, Event #911 is an ECU software upgrade for both HEVs and PHEVs. Event #939 is an HCU software upgrade for HEVs and Event #940 is an HCU software upgrade for PHEVs.

This TSB is NOT being applied to all 2022-23 HEV/PHEV Tucsons. When my VIN is input into the Hyundai system the TSB does not come up as being needed. Hyundai may only be approving the warranty work to install the TSB for the stated symptoms: "increased oil consumption" or "white smoke." You might have to educate your Hyundai dealer's service department about the existence of the TSB and then convince them that a failed lab test for the oil or an oil level above the maximum fill line make your car eligible for the TSB because of the oil being diluted by gasoline.

After applying the TSB the dealer changed my oil. (I confirmed that they used 0W-20 full synthetic oil.) I will note the current oil level and then monitor to see if it rises. If the oil dilution problem does still exist, it may not become evident until next winter.

(Note - These are the DTC error codes also addressed by the semi-secret TSB. I'm listing them here in case somebody is searching the forum for such a code. P1441, P1A77, P00B7, P2118, P0401, P0236, P0299, P2B60.)

Admins - There should be similar TSBs for all other Hyundai and Kia models that use the 1.6L Gamma II turbocharged engine. Please cross-post if possible.