Variable output oil pumps: A ticking time bomb for VW 3.0 TDI engines

For a diesel engine to please the driver while also meeting stringent emission standards, it must be equipped with a range of solutions, not always beneficial for the engine itself. One of these is adjustable oil pressure, which in some engines from the Volkswagen Group can lead to the destruction of the power unit.

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, for years, manufacturers have been somewhat blindly searching for solutions that will reduce this resistance. Experiments involving the use of new materials and lighter, more delicate component constructions end with varying results, sometimes resulting in serious operational problems after low mileage. The durability of modern power units is also highly debatable – it's not what it used to be.

One of the many solutions that were supposed to reduce resistance is the variable output oil pump, which is a pump that pumps oil at different pressures depending on the oil temperature and engine speed. Anyone who understands the basic workings of a car's lubrication system knows that in a traditional pump, the pressure also 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 taking into account not only engine speed but also other factors – such as oil temperature. The main idea is to reduce oil pressure to a safe minimum when oil demand is low. This also reduces engine load to some extent. The exact same trick is used in alternators and coolant pumps, and a few of these subtle changes in engine accessories result in one significant effect – reduced resistance.

Variable output oil pumps are not a new solution. They have been used for many years and usually do not cause major problems. Although the description of such a pump's operation may cause concern among conservative mechanics, in practice, it does not pose a significant threat. 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 has been meeting the Euro 6 standard since 2014 (usually the car's model year is 2015-2017). Workshops mainly servicing cars from the German group (VW, Audi, Porsche) have known about this problem for years.

Some 3.0 TDI engines do not endure 300,000 kilometres, which was not a major problem when they met Euro 4 and 5 standards. Seizing usually occurs in the range from about 100,000 to 300,000 kilometres. However, there were cases where the engine did not last the warranty period, seizing after just tens of thousands of kilometres.

After years of digging into the issue 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. It’s enough to look into the ECU maps to discover the problem.

The ECU maps reveal very low oil pressure at low and medium engine speeds. It does not increase with speed as in traditional oil pump designs 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 equipped with the 3.0 TDI engine have automatic transmissions, which usually shift gears much earlier. This means that for 90% or more of the travelled distance, this engine operates at low oil pressure around 1-1.5 bar. This is roughly half the value commonly considered safe. Of course, engines can safely operate at low oil pressure, provided they are not heavily loaded.

Interestingly, the pressure further drops with the rise in oil temperature. But this is a minor aspect since increased pressure relates to temperatures below freezing. However, at oil temperatures above 110°C at low engine speeds, the pressure also drops slightly but noticeably.

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. This is deadly for the engine.

The CRT unit designation in the Audi A6 C7, which is perhaps the most known for this problem, delivers a maximum of 218 or 272 HP (depending on the type) and respectively 500 or 580 Nm of torque. The peak torque according to catalog data appears already from 1,250 RPM, so one doesn't need to exceed 2,500 RPM to accelerate very efficiently. And here lies the problem.

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

There are two very strong arguments suggesting 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. Here they are:

1. Engines (by engine code) that regularly seize, after increasing their oil pressure, 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 since 2018, they have raised the oil pressure themselves. There are no known cases of evo2 engines seizing after such a low mileage and in the same way as the earlier models.

According to Robert Halicki from 44tuning Performance Center, who knows the issues with 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 (also in newer units, which many mechanics overlook), he himself points mainly to the lubrication system, which in his opinion requires comprehensive improvement. For example, he points out the shape of the oil pan, which causes the lubrication of the engine (especially splash lubrication) to be uneven.

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, as he emphasizes, the engines with the 6.1-quart system can be filled with more oil and should be because they have lubrication deficiencies and a smaller amount of oil degrades too quickly. And this happens 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 quarts. Drivers often drive with too low an oil level after leaving the service or mechanic, unaware that this is happening. There were cars that came to Robert Halicki’s workshop with an actual oil level lower by 1.5-2 quarts than optimal or with oil that was degraded shortly after replacement. Another issue is the incorrect actual oil pressure value, overstated by about 1 bar by the computer, which could mislead an inexperienced mechanic.

Most interestingly, in his opinion, the issue of too low oil pressure also affects 3.0 TDI engines from 2018 or even the newest ones, wherein the manufacturer, instead of the previously used air cooling system (pre-2021 models) via an intercooler (air-to-air cooling system), implemented 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 actually relieve the engine and reduce its internal resistance, as well as resistance in the drive system through proper lubrication with the right oil. He is currently 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.

Essentially, oil pressure control is handled by the computer, so increasing the pressure is a software operation. Of course, first, one checks whether the engine actually has too low a pressure and needs modification. The only mechanical intervention is the replacement of the oil pressure control valve.

There are concerns about whether raising oil pressure in an engine not designed for it will cause damage. As for 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 indeed have a positive impact on 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 sometimes optimizing these parameters can 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. On the market, the cost of such a service ranges from around £100 to £240.

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

Unfortunately, regardless of the brand, there are two paths in engine seizing, and neither is cheap. A repair costs a minimum of about £6,000, and there is no guarantee that this amount will be sufficient. A used engine costs around £6,000 to £8,000, which is also not a low amount. We do not know the condition of such a unit, and one can buy an already partially seized engine. Even raising the oil pressure does not guarantee it will last long.

There is no guarantee, even if you have a car from new, and the engine has already covered over 100,000 kilometres. However, without a doubt, spending a few hundred pounds without a guarantee of a positive effect is better than waiting for a repair several times more expensive.