[AdhirajVW]

Hello BHPians!

My humble VW Ameo 1.5TDI just reached 60,000 kms a few months back and for the first time I decided to get it serviced from outside and not the ASS because of the following reasons:
1. Can see the work being done in front of me
2. Can afford a much better quality of Engine Oil at a lesser service cost.

However, after the service, I witnessed drop in mileage in the vehicle. I thought of giving it some time for it to improve but after 2 months and 3000kms, it is still the same. When I say drop I mean the following:
1. Highway: My car used to give around 24-25km/L on highways, which had dropped to 19-21 now
2. City: Inside the city used to be around 15-17km/L which has dropped to 10-12 now.

I got the below work done:
1. Engine Oil Change: Used Rowe 5W-40. Flushed with AMSOIL before filling the new oil.
2. Oil Filter: Changed with OEM one
3. Fuel Filter: Not changed
4. Air Filter: Since I got a new BMC filter installed at around 50k kms, just got it cleaned with compressed air.
5. Rear Brakes: Got the drum and pads replaced
6. Cabin Filter: Changed with OEM one

One difference which I noticed was that VW service centre filled the engine oil till midway of the min and max mark and now the engine oil is at the max mark (not more).

Can someone help in identifying the reason for the drop? I am concerned if my engine is not getting damaged internally.

[WasavaTyres]

Have you derived these fuel consumption figures on full tank to full tank or the onboard readings ?

[Turbohead]

That Rowe oil is not VW 505 01 compliant. I don't know if that makes a difference.

Plus you would want to check if the O2 sensor has been contaminated by any chance.

Also you would want to check whether your tires are properly inflated- sometimes the gauge at your favourite fuel pump might not be properly calibrated.

[contact.nitin7]

Have you tried checking if the MAF sensor is working properly or not, what readings is it giving?

If I show my car's FE - it'll blow away your mind!

[humyum]

Just a hunch. After a 10-15 kilometer drive, can you touch just the part outside the alloys/steel rims from the center and see if all of them are hot uniformly. Just peck it, it might be very hot but check if its uniform.

This is to rule out a sticky brake pad/lining

Secondly, is 5W40 the recommended grade for your car? Or is it 5W30? If the grade was changed from 30 to 40, economy will take a hit but not to the extent you have mentioned.

[vishy76]

I would recommend getting the fuel filter changed as well. It's not a good habit to prolong fuel filter changes on a diesel here in India since diesel quality in general is patchy. Anything beyond the 15K km mark is stretching it. Contaminants in the fuel can be detrimental to the life of expensive ancillaries such as the high pressure fuel pump and especially the injectors.

Secondly, check the MAF sensor. Since you are running an aftermarket air filter which is cleaned using oil, it might have caused the MAF to get clogged. If the engine thinks the air entering the intake is less, it will automatically increase fuel to compensate. Cleaning the MAF sensor isn't all that difficult either.

Lastly, if majority of the mileage you have clocked has been in the city or has included short trips, it's advisable to get the intake manifold, anti shudder valve (throttle body) and the EGR system (EGR valve, cooler, return pipe) cleaned up thoroughly. I have noticed this improves fuel economy quite a bit. This is a labour intensive task, so better to keep it for the end.

Originally Posted by Turbohead

That Rowe oil is not VW 505 01 compliant. I don't know if that makes a difference.

Based on what I have read, the 505 01 spec of oil had originally been prescribed by VW for the PD engines where the high pressure pump is driven by a lobe on the camshaft. This spec of oil was prescribed to offer extra protection to that lobe. I know several TDIs running 505 00 and not having any issues wrt fuel economy or longevity.

Originally Posted by humyum

Secondly, is 5W40 the recommended grade for your car? Or is it 5W30? If the grade was changed from 30 to 40, economy will take a hit but not to the extent you have mentioned.

The recommendation for the TDIs is 5W40 fully synthetic oil.

[Rohit Tripathi]

Hi Adhiraj,
I have a 2015 tdi vento and sharing my view. I think the fuel filter should be changed as this will impact your injectors. Tyre alignment, pressure, oil ratings should be as per vw specs.

I recently traveled to Pune and Hyd in Nov and one of the injector failed near Belgaum. Before this while there was no drop in performance but after replacing the injector in Belgaum the milage went up from 21 to 24. I use 15 inch 205 yokohama s drives.
Hope this useful.

[JoshMachine]

Originally Posted by AdhirajVW

Can someone help in identifying the reason for the drop? I am concerned if my engine is not getting damaged internally.

As others have quoted, replacing your fuel filter, in a diesel car, is the first thing that you should do.
I too drive a VW 1.5 TDi car, and have to strictly adhere to the replacement regime every 10k km or so.

Besides straining the 'fuel line' due to inefficient capture of the dirt and dust, a faulty fuel filter (that is not replaced for quite some time) will also wear the fuel pump and injectors.
The obvious effect that you see will be reduced/sluggish engine power and reduced fuel efficiency.

[AdhirajVW]

Originally Posted by JoshMachine

As others have quoted, replacing your fuel filter, in a diesel car, is the first thing that you should do.

Thanks. Will get that done. But that still doesn't explain the drop in mileage immediately after the service.

Originally Posted by vishy76

I would recommend getting the fuel filter changed as well. It's not a good habit to prolong fuel filter changes on a diesel here in India since diesel quality in general is patchy. Anything beyond the 15K km mark is stretching it. Contaminants in the fuel can be detrimental to the life of expensive ancillaries such as the high pressure fuel pump and especially the injectors.

Secondly, check the MAF sensor. Since you are running an aftermarket air filter which is cleaned using oil, it might have caused the MAF to get clogged. If the engine thinks the air entering the intake is less, it will automatically increase fuel to compensate. Cleaning the MAF sensor isn't all that difficult either.

Thanks will get all these done. I have a feeling that cleaning the air filter with compressed air was not a good idea and might have clogged the MAF. On the BMC site they have strictly warned against cleaning with compressed air.

[Piyush Kanthak]

Don't know about fuel efficiency but definitely there was a bit of power loss after a clutch plate change in my SX4 aftermarket, first she used to idle at around 1500 to 100 RPM and now she idles at 600 RPM.

[roadrunner_nv]

By any chance, was your ECU flashed by the service guys recently? The dieselgate fix was a major irritant for my Rapid and it does cause the fuel efficiency to drop. It did in my case.

[micky]

Did you get any resolution to this ? A friend is stuck in a similar situation with his Ameo 1.5D. Efficiency dropped to half after the service.

[amitkuch]

I am facing the same symptoms with my Creta Diesel BS6. I am a very light foot driver and it helps me to get mileage in range of 19-21 Kmpl. The car was sent to HASS for Third service with the odometer reading of 19722 Km. After the service, Creta is giving terrible readings of mileage on MID and actual mileage while calculated for tank to tank.
I went to the service center and as usual the senior mechanic started looking for any error code on his tablet, and there was none. He asked me to finish the tank and then calculate the mileage on tank to tank basis. It came just 17.24 Kmpl, which is the lowest ever for this car, as I am regularly tracking my car mileage on Fuelio app. This result difference is for fuel filled on same petrol pump, same driver, same driving style.
The other thing I noted that generally after filling the fuel tank full, DTE readings were in range of 950-975 km but this time it only show 864 Km.
I again went to the service center again and asks senior mechanic have a look on Mass air flow sensor. He told me that this car is highly advanced and any engine related problem will result in glowing CEL. However he still cleaned the air filter and MAF sensor and removed the negative terminal of the car to help it reset, if anything is wrong. Just before that moment DTE reading was 857 Km, which changes to 900 Km after connecting the terminal.
I was little bit relaxed to see that and thought finally the issue is resolved now. But it was temporary relief as the car continue to give poor mileage figures on MID. Post that day the car has run a distance of 690 Km and showing the mileage of only 17.4 Kmpl on MID.
A few more observations:-
1- For highway trips previously MID shown a high mileage of 21-24, which eventually settled for 19-20 for a full tank. Those high trip mileage are now at 18 kmpl max. I once extracted trip mileage of 30 Kmpl for a distance of 60 Km on Delhi-Meerut Expressway with AC off.
2- Mileage reading in MID drops very fast while idling if I compare that before service level.
After reading a bit on internet, I think that there is something wrong with the MAF sensor. I request all members to please suggest what to do ?

[AdhirajVW]

Hi, So finally the issue was resolved a month back. Tried everything but the issue was because of something which I didn't think could have caused a mileage drop. The service centre guys had overtightened the lug nuts after the rear drum change and the front disk service. The wheels because of not being able to move freely needed the engine to work harder and hence the mileage drop. Front brake disks were affected as well. Might need to change them. Definitely not going back to the stupid service center anymore.