I had my Seat Leon 1.6tdi 2014 serviced a week ago and from the first day after the service until now the MPG is terrible around 20 mpg less can't even get it over 60mpg prior to the service the worst I got was 63mpg but I was consistently getting 68-75mph and on occasion 80-86mpg. Not sure why this has happened any ideas? Wrong oil type? Wrong fuel filter?
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MPG much lower after a service
- Thread starter d_taddei2
- Start date
Hi I have checked both spontaneous and average, but I normally go by the average. Similar journeys and same types distance and road surfaces, I did the exactly the same journey the difference was 25mpg less which I think is pretty obvious something not right. If it had been 1-5mpg difference I wouldn't really notice but 25mpg is a big difference the hasn't been over 60mpg and struggles to get even 55mpg mostly 45-50mph now when before my worst was 63-65mpg
There are three averages! - which one did you used to use, and which one is it on now?
1. long term?
2. since refuel?
3. current journey?
Try toggling between them?
Everyone knows (should know) TDI's use 507 spec oil which is 5w30 or 0w30 - There is no way using the wrong oil would loose you 25mpg!
Was this a main dealer - or an independent?
1. long term?
2. since refuel?
3. current journey?
Try toggling between them?
Everyone knows (should know) TDI's use 507 spec oil which is 5w30 or 0w30 - There is no way using the wrong oil would loose you 25mpg!
Was this a main dealer - or an independent?
Hi I always use current journey, I have done over 200 miles since service, the car was reset during service and again a week later when I had the recall on the airbag done, the issue is the same. It's an Independent garage and car has been serviced there before. I still have to check the air filter as I read online that if it's not fitted correctly or wrong one it gets the mix wrong and uses more fuel apparently. The car drives normally.
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I don't see how a garage could incorrectly fit a flat panel filter? unless they left a rag in there!
What did they do? Just an oil/filter change?
Have you got an OBD2 bluetooth reader? I think I would scan for fault codes to see if anything comes up for your DPF/alternator/AC compressor?
Could you have had a bad batch of fuel? If that's even possible?
When was the last time it had a fuel filter? though if the fuel filter is blocked you should get a warning and limp mode.
What did they do? Just an oil/filter change?
Have you got an OBD2 bluetooth reader? I think I would scan for fault codes to see if anything comes up for your DPF/alternator/AC compressor?
Could you have had a bad batch of fuel? If that's even possible?
When was the last time it had a fuel filter? though if the fuel filter is blocked you should get a warning and limp mode.
The air filter on the TDI is really simple to change. The case is screwed together, not clipped - not sure how a garage could get that wrong! easy for you to check - just 7or8 screws to undo.
Don't assume the fuel filter has been replaced. They are not 'normally' replaced as part of an anual service -
You don't have 'plugs' on your diesel - unless you are referring to glow plugs, which are not a service item, like spark plugs on a petrol.
Hi I checked the air filter all is good although I did notice one screw wasn't screwed down but I think it unlikely to be the cause. Fuel filter is normally replaced when I get a service although I did notice the oil dipstick seems to be pretty full at maximum I think maybe over filling could be an issue????
Oil at the full mark on the dip stick is fine, and as I would expect from a recent service.
If its ABOVE the full/max mark then that is not good.
I checked the invoice oil used was 5W-30 LS. Oil, air, and fuel filter were changed. Spoke to garage they said only thing it can be is a possible vacuum leak and it's drawing air in. Fuel has been ruled out due to no evidence. Still struggling to think what else it could be, today fuel consumption was worse.
Quick q - where do you fill up? Only reason I ask is my friend filled up (cheapest in the area by about 10p) about 6-7 weeks ago and his tdi has gone down economy wise and even though he's filled up since the mpg is still down so there could be a batch if poor diesel around??
Hi I fill up at the same garage each time at ESSO. I was still using the same tank of fuel that I was getting 73-78mpg in then went in for a service and suddenly down to 35-55mpg. It's also been in for the recall and I feel it's gotten worse. A week before the service I even managed to get 86.4mpg driving A and B roads over 40 miles distance.
Ah ok its most likely not fuel then, have you noticed any difference in performance? And when you were getting the frankly excellent mpg was that based just on the trip computer or did you also do the brim to brim calculation?
@d_taddei2 - A couple of factors that might be contributing to your mpg reduction;
- I believe that filling stations switch to selling winter diesel fuel around this time of the year and winter diesel has a lower energy density. This - and the colder weather - will contribute to poorer mpg; around 5%-10% is suggested from an internet search). From memory when I last owned a diesel around 10-11 years ago, my winter mpg would worsen by around 5%.
- If your car’s DPF has become clogged up with particulate matter, it’s likely to be going through frequent regenerations to try and clear it and this is likely to have a noticeable detrimental impact on fuel consumption (I’ve seen a 10-20% worsening mentioned from an internet search). As @SuperV8 has suggested above (post #6) a scan for DPF-related fault codes would be worthwhile to either confirm or eliminate the DPF as the cause - or a contributory factor - to your mpg worsening.
Rather than relying on the cars onboard computer, always fill the car to the brim and keep a log of the fuel added and mileage covered. This will tell you the actual miles per gallon.
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