VW's variable oil pump: Saving emissions, destroying engines

A diesel engine must be equipped with various solutions that are not always beneficial for the engine in order to please the driver while also meeting stringent emission standards. One of these is adjustable oil pressure, which can destroy power units in some Volkswagen Group engines.

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, often resulting in increased resistance. Therefore, manufacturers have been searching for solutions to reduce this resistance for years. Experiments involving new materials and lighter, more delicate component constructions have yielded varying results, sometimes leading to severe operational problems after low mileage. The durability of modern power units is also highly debatable; it's not what it used to be.

The variable output oil pump is one of the many solutions to reduce resistance. This pump adjusts oil pressure depending on the oil temperature and engine speed. Anyone who understands the basics 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, thereby reducing engine load to some extent. This approach is also used in alternators and cooling liquid pumps. These subtle changes in engine accessories result in slightly 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 of the 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 has been meeting the Euro 6 standard since 2014 (the car's model year is usually 2015-2017). Workshops primarily servicing vehicles from the German group (VW, Audi, Porsche) have been aware of this problem for years.

Some 3.0 TDI engines do not endure 186,000 miles, a major issue compared to their performance under Euro 4 and 5 standards. Seizing usually occurs between about 62,000 and 186,000 miles. In some cases, the engine did not last through the warranty period, seizing after tens of thousands of miles.

After years of investigation by specialist companies, the primary culprit was the variable output oil pump. Specialists are convinced it's the main, though not the only, cause. Problems can be discovered by examining the ECU maps.

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

The issue is that cars equipped with the 3.0 TDI engine have automatic transmissions that usually shift gears much earlier. This means that for 90% or more of the traveled distance, these engines operate at low oil pressure around 15-22 psi, roughly half the value commonly considered safe. While engines can safely operate at low oil pressure under light load, this is not ideal.

Interestingly, the pressure further drops as the oil temperature rises. However, this is a minor aspect since increased pressure concerns temperatures below freezing. At oil temperatures above 230°F at low engine speeds, the pressure also drops slightly but noticeably.

Unfortunately for durability, the 3.0 TDI unit has enormous torque, runs smoothly, and consumes relatively little fuel, considering it often exceeds 200 HP. 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 the most well-known for this problem, delivers a maximum of 218 or 272 HP (depending on the type) and 369 or 427 lb-ft of torque, respectively. According to catalog data, peak torque appears as early as 1,250 RPM, so one must not exceed 2,500 RPM to accelerate efficiently. 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-environmental solutions. They successfully use a popular method to prevent engine seizing: reprogramming the ECU map responsible for pressure control. After this correction, the pressure is significantly higher.

Two strong arguments suggest that the main, if not the only, 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 as frequently, despite meeting even stricter Euro 6 d-Temp emission standards. The factory map has higher oil pressure, even 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 and in the same manner as the earlier models.

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

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

He notes that the EA 896 3.0 TDI units have an over 8-quart lubrication system, while the EA 897 units have just over a 6-quart system. However, he emphasizes that the engines with the 6.1-quart system can be filled with more oil than specified and should be, as lubrication deficiencies and a smaller oil volume lead to quicker degradation. This happens irrespective of the production year, indicating that oil pressure maps are not necessarily the root cause of the problem. The evidence below supports this view.

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 can be up to 1.5 quarts. Drivers often drive with an oil level that is too low right after a service or mechanic visit, unaware of this discrepancy. Some cars that came to Robert Halicki's workshop had an actual oil level lower by 1.5-2 quarts than optimal or had oil degraded shortly after replacement. Another issue is the incorrect oil pressure value, overstated by about 14 psi by the computer, 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. In these newer models, 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 involving coolant). Consequently, the charging system temperatures are often significantly higher, engine oil degrades much faster, and the units generate more soot.

According to Robert Halicki, increasing the oil pressure might be the finishing touch, but only after making changes that relieve the engine and reduce its internal resistance, as well as resistance in the drive system through proper lubrication with the correct oil. He is working on a further project to increase the amount of oil in the system and improve its filtration efficiency. For customers, he creates custom oil compositions, which, in his opinion, work much better than the oil recommended by the manufacturer. He does not specify 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 manages oil pressure control, so increasing the pressure is a programming operation. Of course, one must first check whether the engine has too low a pressure and needs modification. The only mechanical intervention required is replacing the oil pressure control valve.

There are concerns about whether raising the oil pressure in an engine not designed for it might cause damage. Regarding seals, practice shows it does not. As for durability, practice indicates that it can significantly improve longevity.

– Raising the 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 considered and performed by an experienced mechanic to avoid potential engine damage. Car designers design engines with specific parameters in mind, but optimizing these parameters can sometimes enhance engine performance and durability. In any case, consulting a specialist before making any changes to the engine lubrication system is recommended.

The cost depends on the location, workshop, and scope of work. The price varies mainly based on whether you get a ready-made program (the cheapest option) loaded into the ECU or opt for the complete service of reprogramming the ECU and replacing the valve. Such a service ranges from around $120 to $290 on the market.

According to specialists in German engines, similar issues are observed in other six-cylinder units from the Volkswagen Group. This includes gasoline engines like the 2.9 TFSI, 3.0 TFSI, and 4.0 TFSI. This problem affects cars across brands that use these units, particularly concerning Porsche, where engine replacement costs can be significantly higher than in an Audi or Volkswagen.

To be honest, there is no guarantee, even if you have owned the car from new, that the engine will last beyond 62,000 miles without issues. However, spending a few hundred dollars on preventative measures, even without a guarantee of success, is undoubtedly preferable to facing repair costs several times higher.