VW's 3.0 TDI engines: Variable oil pump blamed for early failures

For a diesel engine to please the driver and meet stringent emission standards, it must be equipped with various solutions, which are not always beneficial for the engine. One such solution is adjustable oil pressure, which can destroy power units in some engines from the Volkswagen Group.

There are only two ways to reduce engine emissions: reducing engine and car resistance and using filters on the exhaust system. The latter has already reached the point of absurdity and often results in increased resistance. Therefore, manufacturers have been somewhat unthinkingly searching for solutions to reduce this resistance for years. Experiments involving new materials and lighter, more delicate component constructions end with varying results, sometimes causing severe operational problems after low mileage. The durability of modern power units is also highly debatable – it's not what it used to be.

One solution that was supposed to reduce resistance is the variable output oil pump, which pumps oil at different pressures depending on the oil temperature and engine speed. Anyone who understands the essential workings of a car's lubrication system knows that in a traditional pump, the pressure changes smoothly, depending on engine speed. But that's the only parameter that affects it.

Variable output oil pumps are designed to control oil pressure by considering engine speed and other factors, such as oil temperature. The main idea is to reduce oil pressure to a safe minimum when oil demand is low. This reduces engine load to some extent. The same principle is used in alternators and cooling liquid pumps, and a few of these subtle changes in engine accessories result in reduced resistance.

Variable output oil pumps are not a new solution. They have been used for many years and usually do not cause significant problems. Although describing such a pump's operation may cause concern among conservative mechanics, it does not pose a substantial threat in practice. Unfortunately, it didn't quite work out in some Volkswagen Group engines.

The widespread seizing of 3.0 TDI engines has been known for several years. This involves units from the EA897 EVO family, which have been meeting the Euro 6 standard since 2014 (typically cars from model years 2015-2017). Workshops mainly servicing vehicles from the German group (VW, Audi, Porsche) have known about this problem for years.

Some 3.0 TDI engines do not endure 300,000 km (186,000 miles), which was not a significant problem when they met Euro 4 and 5 standards. Seizing usually occurs in about 100,000 to 300,000 km (62,000 to 186,000 miles). However, there were instances where the engine did not last the warranty period, seizing after just tens of thousands of miles.

After years of investigation by specialist companies, the main culprit was identified – the variable output oil pump. Specialists are convinced it's the primary, though not the only, cause. Examining the ECU maps reveals the problem.

The maps show low oil pressure at low and medium diesel engine speeds. Unlike traditional oil pump designs, the pressure does not increase with speed because the ECU and control valve keep the pressure low. Only after exceeding about 2,500 RPM does the pressure reach an acceptable level.

The problem is that cars with the 3.0 TDI engine have automatic transmissions, which usually shift gears much earlier. Consequently, for 90% or more of the travelled distance, this engine operates at low oil pressure around 100-150 kPa (15-22 psi), roughly half the value commonly considered safe. Of course, engines can operate safely at low oil pressure, provided they are not loaded.

Interestingly, the pressure drops further with rising oil temperature. However, this is a minor aspect since increased pressure pertains to temperatures below freezing. The pressure drops slightly but noticeably at oil temperatures above 110°C (230°F) at low engine speeds.

Unfortunately (for durability), the 3.0 TDI unit has enormous torque, operates smoothly, and consumes relatively little fuel, considering it often has over 200 HP. Therefore, the most enjoyable driving involves using low speeds and intensive acceleration, which is deadly for the engine.

The Audi A6 C7's CRT unit designation, perhaps best known for this problem, delivers a maximum of 218 or 272 HP (depending on the type) and 500 or 580 Nm of torque (369 or 427 lb-ft). According to catalog data, the peak torque appears already from 1,250 RPM, so one can accelerate very efficiently without exceeding 2,500 RPM. And here lies the problem.

According to specialists dealing with 3.0 TDI engines, there is no other possibility. However, they do not exclude other intermediate factors affecting these engines' reduced durability, such as using other pro-ecological solutions. They successfully use a popular method to prevent engine seizing, reprogramming the ECU map responsible for pressure control. After this adjustment, the pressure is significantly higher.

There are two strong arguments suggesting that the leading cause of these units seizing is the variable output oil pump, specifically the control maps for this pump:

1. Engines (by engine code) regularly seize after increasing their oil pressure and withstand much higher mileage.
2. Newer engines from 2018 (EA 897 evo2) no longer seize so frequently, despite meeting even higher Euro 6 d-Temp emission standards, but the factory map has higher oil pressure, even over 50% more.

Among mechanics, it is believed that Audi (the constructor of this engine) somewhat admitted where the problem lies because they have raised the oil pressure themselves since 2018. There are no known cases of EVO2 engines seizing after such low mileage as the earlier models.

According to Robert Halicki from 44tuning Performance Center, who knows the issues with 3.0 TDI engines, there are multiple causes for the seizing problem. He also disagrees with the opinion that units from 2018 onwards have no lubrication issues.

Although he does not exclude the eventual necessity of oil pressure correction (also in newer units, which many mechanics overlook), he mainly points to the lubrication system, which requires comprehensive improvement. For example, he points out the shape of the oil pan, which causes the engine's lubrication (especially splash lubrication) to be uneven.

He notes that the EA 896 3.0 TDI units have an over 8-litre (8-quart) lubrication system, while the EA 897 units have just over a 6-litre (6-quart) system. However, as he emphasizes, the engines with the 6.1-litre system can be filled with more oil in reality, which should be done because it has lubrication deficiencies and a smaller amount of oil degrades too quickly, regardless of the production year, indicating that oil pressure maps are not necessarily the root cause of the problem. The studies below show this.

Another issue is the electronic oil level indicator, which misleads the user or mechanic. The difference between the computer's reading and the actual value is up to 1.5 litres (1.5 quarts). Drivers often drive with too low an oil level right after leaving the service or mechanic, unaware of this. Cars arrived at Robert Halicki’s workshop with an actual oil level lower by 1.5-2 litres (1.5-2 quarts) than optimal or with oil degraded shortly after replacement. Another issue is the incorrect actual oil pressure value, overstated by the computer by about 100 kPa (14 psi), which could mislead an inexperienced mechanic.

Interestingly, in his opinion, the issue of oil pressure being too low also affected 3.0 TDI engines from 2018 or even the newest ones. The manufacturer replaced the previously used air cooling system (pre-2021 models) via an intercooler (air-to-air cooling system) with a heat exchanger (air cooling with coolant involvement). In these, the temperatures in the charging system are often significantly higher, engine oil degrades much faster, and the units generate much more soot.

According to Robert Halicki, increasing the oil pressure might be the finishing touch, but only after making changes that will relieve the engine and reduce its internal resistance and resistance in the drive system through proper lubrication with the correct oil. He is working on a project to further increase the amount of oil in the system and its more efficient filtration. For customers, he creates custom oil compositions, which, in his opinion, work much better than the oil recommended by the manufacturer. He does not indicate which oil available on the market should be used to extend the 3.0 TDI engines' lifespan because he believes such oil does not exist.

The computer controls oil pressure, so increasing the pressure is a program operation. Of course, one first checks whether the engine has too low a pressure and needs modification. The only mechanical intervention is replacing the oil pressure control valve.

There are concerns about whether raising oil pressure in an engine not designed for it will cause damage. Regarding seals, practice shows it does not. Regarding durability, practice shows that it goes a long way.

– Raising oil pressure in a 3.0 TDI engine can positively impact its operation, says Witold Kania, manager of the ProfiAuto – Michalski Car Service workshop – especially at low and slow speeds, improving lubrication and cooling of engine components. However, changing the oil pressure should be carefully thought out and done by an experienced mechanic to avoid potential engine damage. Car designers design engines with specific parameters in mind, but optimizing these parameters can sometimes improve engine performance and durability. In any case, consulting a specialist before making any changes to the engine lubrication system is recommended.

It depends on the location, workshop, and, primarily, the scope. The price mainly depends on whether you get a ready-made program (the cheapest option), which is only loaded into the ECU, or whether you opt for the complete service of reprogramming the ECU and replacing the valve. Such a service ranges from around $160 to $390 CAD on the market.

According to specialists in German engines, similar cases are observed in other six-cylinder units from the Volkswagen Group. It concerns gasoline constructions of 2.9 TFSI, 3.0 TFSI, and 4.0 TFSI. This affects cars of every brand that uses these units, paying particular attention to Porsche, where replacing an engine due to the brand alone can be significantly more expensive than replacing an Audi or Volkswagen.

There is no guarantee, even if you have a car and the engine has already covered over 100,000 km (62,000 miles). However, spending a few hundred dollars without guaranteeing a positive effect is better than waiting for a repair several times more expensive.