Psa faces unexpected issues with 1.2 PureTech engine degradation

The topic of the 1.2 PureTech engine continues to generate buzz online. In one of MotoFocus' service programs, an interesting conversation was held with a representative from a company that supplies timing belts. It emerged that the problem of belt degradation might have been known even before the engine was put into production.

Editor Witold Hańczka from Motofocus.pl interviewed Roman Boluk, a representative and expert from Continental, which manufactures spare parts, including rubber elements like timing belts. When he asked about the 1.2 PureTech unit, Boluk responded, "The main problem with this engine is the fuel flow into the engine oil."

According to the expert, gasoline mixed with oil forms a "very aggressive mixture in the lubrication system, which severely interferes with the structure of the timing belt."

The expert says that Continental conducted studies even before engine manufacturers wanted to introduce the solution of the timing belt working in an oil bath. Various compounds that could appear in the engine oil, including fuel, were added during the tests. A 5% addition of gasoline to oil causes 30% greater belt degradation. The degradation process is, of course, more intense as more gasoline gets into the oil.

From the conversation, we learn that Continental was not the supplier of the original belts. Still, Roman Boluk does not believe that the belt supplier did not conduct similar studies as every reputable manufacturer. PSA likely received the results of such studies and knew about the belt degradation issue even before this solution was implemented. This does not mean, however, that the information about belt degradation was ignored. In one of its statements, the company assured that the engine would be extensively tested.

The statement reads: "By the time it hits the market, the three-cylinder turbocharged gasoline engine PureTech will undergo a rigorous testing program including over 46,000 hours on the engine test bench and over 1,600,000 kilometres (994,000 miles) driven during test drives."

Perhaps this intensity of testing misled the group responsible for implementing the engine into production. As is known, even from the users themselves, vehicles that are used quite intensively do not generate excessive problems. It is usually the individuals whose cars have low, not high, mileage who complain.

The Continental expert makes similar observations, explicitly stating that not everything can be checked in the testing phase, and it takes time and a large number of vehicles to get the whole picture. This is similar to implementing almost any product, which undergoes the final testing phase on a consumer group. For example, the fourth phase of drug tests is already conducted on patients after the drug has been introduced to the market. It's precisely the same with vehicle testing, and it's no secret.

As I wrote in the article about the 1.2 PureTech engine, the biggest problem with the PureTech engine, which is known to a narrow group of mechanics, is not the timing belt itself but what Roman Boluk mentioned, which is the impact of gasoline on oil degradation and thus belt degradation.

The large extent of gasoline infiltration into the oil could have surprised the manufacturer. Even with test results and information about gasoline's impact on the belt, PSA might not have known that this adverse phenomenon would occur on such a large scale. Therefore, when the 1.2 engine was put into production, it did not expect such an intense problem related to oil degradation.

It is worth noting here that gasoline infiltrating the oil in the PureTech engine has many more consequences, including excessive oil consumption due to worn piston rings, numerous pre-ignitions leading to spark plug damage, and carbon buildup, which in turn blocks the piston rings and deepens the phenomenon of pre-ignitions and oil consumption.

The timing belts are not the problem; their replacement is not the solution. The Continental expert points out that timing belts are always high-quality products, and there are no so-called economic lines because this is a part that also impacts vehicle safety. Breaking the belt while driving could pose a traffic hazard. It is also worth noting that in the 1.2 PureTech engine, the belts do not break, and at least such cases are sporadic. Given the conditions in which the belt operates, it is still highly durable.

Therefore, the real solution to the problem is to eliminate the phenomenon of gasoline infiltrating the oil, and perhaps that is why new software is often installed along with a visit to Stellantis's service. What a user can do for their 1.2 PureTech engine car is to limit or completely stop using the start & stop system, reduce driving on very short distances, and limit excessive engine load, for example, by driving at very low RPM with the accelerator pedal pressed harder.