Fuel consumption issues on 1.9 TDI PD 131PS engines

Hello.

I have a quick question about the fuel consumption of the vehicles in our company fleet. We have:

- Passat 3BG Variant Trendline, 1.9 TDI, 131 hp, 6-speed manual transmission.
- Passat 3BG Variant Trendline, 1.9 TDI, 131 hp, 6-speed manual transmission.
- Passat 3BG Variant Highline 1.9 TDI 131 hp - with Tiptronic transmission.

Now, we're seeing some very strange fuel consumption figures with these vehicles. They all have the same load (or no load), and the fuel tank capacity is the same. All the winter tires being tested are the same model, and they were all tested by the same driver using the same driving profile on the same route.

The first Passat has been showing an average fuel consumption of 5.9 liters per 100 kilometers on the MFA 2 display for quite some time. The second one achieves a fuel consumption of 7.4 liters per 100 kilometers, while the Highline model with Tiptronic achieves 7.1 liters per 100 kilometers.
In all cases, the fault memory is clear, and the measured values are plausible.
The question is, why is the consumption so high for 2 of these boxes?
The second trendline indicates a fuel consumption of 7.7 liters per 100 kilometers at speeds of 140-160 km/h, while the Highline model achieves approximately 7.0 liters per 100 kilometers at speeds of 140-160 km/h on the highway.
The first one achieves a fuel consumption of 6 liters per 100 kilometers.

I don't really consider 7L/100km to be particularly economical for a 1.9 TDI. I personally own an Audi A6 C4 2.5 TDI Quattro with 140PS (175PS), and it has been running with a consumption of 6.8 - 7.2L/100km since I've owned it. But it has all-wheel drive, is 300 kg heavier, and has 600cc more displacement and one more cylinder.
That gives me reason to believe that something isn't right with those two 1.9 engines.
The question is only what.

Are there any factors that can significantly increase fuel consumption in a 1.9-liter common rail diesel engine? Does anyone have any experience with that?
Especially when it comes to fuel prices, a car like that should be relatively inexpensive to run .

Perhaps someone can give me the crucial tip I need.

Thank you in advance, and have a nice Sunday.

Because they have a leak in one of the charge air hoses, causing high fuel consumption?

Hi.

Okay, so far, the intercooler system seems to be fine for everyone. Everything is sealed, and there are no whistling noises. Everyone is still using the original mass airflow sensor (on the Highline model, it only measures up to a maximum of 800mg/h, in every gear at full throttle and high RPMs - a new one has been ordered).
The boost pressure closely follows the target values. Slight over-revving observed at 1900 RPM across all vehicles.

I want to start looking for a job at the AGR tomorrow.
The vehicles that were running initially only drove for the first 150,000 kilometers mostly in the city. It really started to make a difference after about 30,000 kilometers.
I definitely want to take the intake manifold off and verschandeln it of carbon buildup sometime.

But does it really matter that much?
The timing belts have been replaced for all 3 recently at a VW service center!

There were numerous engine control units (ECUs) and software versions for the 130PS engine. Are these all the SAME? The background was different equipment, for example, with the PDE. 550 and the PDE. 520, etc.

Furthermore, different weights, wheel/tire combinations (including tire pressure), payload capacities, and equipment options all play a significant role. Therefore, it's impossible to directly compare two passenger cars. Also, the driver's skill and style are factors to consider. Driving profile, acceleration behavior (right foot), etc.

I did not consider the engine control units or software versions in this case.
I can only tell you that all the vehicles are from the year 2004.

The tires on all three vehicles are good Bridgestone Blizzak LM32 tires. Air pressure is also okay.
People are always watching. The manager emphasizes the importance of maintenance.
The weights should all be nearly identical.
More than a small toolbox can fit in the trunk of most vehicles. The Highline model is an exception, as its trunk is often completely full, yet it still achieves a lower fuel consumption than the Trendline model. Although it's a Tiptronic!
To rule out the possibility that the issue was with the driver, the cars were already swapped between drivers.
For the Passat, which is inherently more fuel-efficient, to achieve the fuel consumption figures of the 2.0 or 3.0 liter models, you would have to drive it quite aggressively.

If you drive like an old man, setting the cruise control to 90 km/h, you can achieve a fuel consumption of around 5.5 liters per 100 km. Even the first Trendline model can achieve this, but at 130 km/h with cruise control on the route Frankfurt -> Hannover -> Frankfurt! They're back to consuming around 7 liters per 100 kilometers.
That's really weird. Because the fuel consumption is higher than that of my 2.5 TDI (R5) Avant Quattro on this route!
Is such high variability in consumption really only due to the software? Our boss should have kept the 3B with the AFN engine instead. He always drove with a fuel consumption of 5-6 liters per 100 kilometers .

To the best of my knowledge, the license plate codes 019KD and 019GQ were issued in 2004.

The weights should all be nearly identical.

It can't be. An automatic transmission is always different from a manual transmission . And to be able to make clear and more accurate calculations, you would have to weigh the cars. And then you would have to drive them on standard laps (with the same driver/driving profile). Depending on the driver, factors like weather, wind, and distance can easily account for a difference of 1 liter of fuel.

In my opinion, the whole thing is a pointless endeavor.

You didn't understand...
Despite the automatic transmission being heavier, having a fully loaded trunk, and being an automatic (which typically consumes more fuel), it still uses less fuel than the Trendline manual transmission, which lacks features like the navigation system, leather upholstery, and a trailer hitch.
As I mentioned, it needs more than my 2.5 Quattro, which already weighs 300 kg more according to the registration documents.
We're not talking about differences of just 0.2 - 0.3 liters per 100km; we're talking about differences of up to 2 liters per 100km, which is a significant amount!

2L... that's how much fuel a Lupo 3L uses for 66 kilometers.

I absolutely understand.

You're comparing apples and oranges. An accurate statement, or even any statement at all, requires technical equality. The drivers must be the same, the driving profile must be the same, the weather must be the same, the route must be the same, the weights must be the same, the engine control units (including software versions) must be the same, and the technical condition must be the same (including wear and tear, etc.). This is not the case here, which is why you'll always get different values based on the principle. Here it's 0.1 liters, there it's 0.1 liters. LLK or the introduction of something that contaminates it - 0.01 liters.

Ultimately, it's always different. And technically, it can't be any better. Cars are just as diverse as people.

That can't be right. An automatic is always different from a manual . To be able to make clear and more accurate calculations, you would have to weigh the cars. And then drive standard laps (with the same driver/driving profile). Alone, factors like weather, wind, and distance can easily account for 1 liter of fuel consumption, depending on the driver.

In my opinion, the whole thing is a pointless endeavor.

Okay, so you're saying that two identical cars, technically sound, with the same equipment and the same load (okay, one might have a tow hitch), can still have a difference of 2 liters per 100 kilometers in fuel consumption.
Especially when dealing with 2 or 3 cars that travel the same routes (sometimes in a convoy).

And it's also normal in your eyes that a 1.9 TDI in a Passat consumes more fuel than a heavier Audi A6 Quattro with 175 hp and full equipment...

Very interesting

I drove the Passat myself, on the route I drive twice a week. When I go up north and back, I can see that I need more than what my Audi offers, and that just doesn't seem right.
But you probably see it differently, right?

The Audi MFA (Multi Function Display) readings are, on average, off by more than 1 liter. Furthermore, the CW values, weights, and configurations/software are completely different.

If you believe that everything is the same, that everything must be technically okay, that all driving routes, temperatures, weather, etc., are identical, then, conversely, the consumption must also be identical.

Then, all the factors that influence consumption are eliminated, and everything written here becomes irrelevant.


(sometimes in a column).

Drafting/convoy driving reduces what? And what does it influence?

'I'm glad my Audi doesn't have an MFA (Multifunction Display), so I have to carefully calculate the fuel consumption at the pump.'
And if my A6 C4 with a 63-liter diesel tank only manages 900km, while the 1.9 TDI in the Trendline only does 800km, then I know something is wrong!


And what about the column? The following car was traveling at 7.1, while the car in front was going at 5.9.
I'm not stupid!

Okay, then it's as I said. EVERYTHING is the same, everything is OK.

Wow, what a mess!
As Mulle already said: if all the conditions are the same, the same amount of energy must be consumed for the same performance. If there are differences, they can be attributed to any of the factors that influence consumption. It seems you yourself have doubts that the technology works equally well in all cases or is in good condition (you mentioned the mass airflow sensor and intake manifold). Please continue searching and then report back.
Or would you like to read that your Audi is the more economical option compared to the VWs?
My 74 kW (leather interior, without trailer hitch, 195 tires in winter, 205 tires in summer) has been consuming 6.4 liters per 100 km (approximately 37 mpg) over a healthy mix of long and short distances (no short trips, etc.) for a good 130,000 km (approximately 80,000 miles), and the intake manifold has remained spotless, surprisingly without any soot.
Otherwise, take a look at the "Spritmonitor" website to see what other people are getting for fuel consumption... I think even for a 96 kW 3BG, it probably starts around 5.x liters per 100 kilometers.
I am unable to translate "haithamina" because it does not appear to be a word or phrase in the German language. It may be a misspelling, a proper noun, or a term from a specialized field. If you can provide more context or clarify the intended meaning, I would be happy to assist you with the translation.

Good evening...

Certainly, my concern isn't that my Audi needs less maintenance.
The differences in consumer reviews for the Passat models are a bit puzzling, since they all seem to have the same engine.

Let's take a closer look at the technology. But things like tire pressure or a stuck handbrake, I can definitely rule out.

Then, first clarify everything that has already been said.

- Leak tightness of the LD line,
-Are all the brakes completely free, is nothing rubbing, are the wheel bearings in good condition, is the underbody protection present and not damaged?
-Software versions and hardware are truly identical.
-...

That reminds me...

Last week, there were some minor issues with the Highline during the inspection.
Initially, the problem was the engine temperature, which consistently stayed below 80°C despite giving it full throttle for 10 minutes after driving 20 kilometers and letting it idle. Then, the measurement had to be repeated five times because the full-throttle readings at 5000 RPM were consistently too high.

I didn't even think about that when I wrote the original post here.