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18-09-2019, 21:03   #1
Sadb
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Suggestions on what could be wrong.

Ok so we had to replace the fuel pump on our 2012 VW Passat. Tbh the mechanic ****ed up the car and we were back and forth for a week to him. Anyway it was replaced properly last Thursday and we put €50 diesel in to the car, the diesel is now in reserve and we’ve only done 301 miles. When I checked a few months back we were getting an average of 52mpg, this week only 30mpg.
Does anyone have any ideas/suggestions as to what could be wrong? Could it be something else that the mechanic did?
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19-09-2019, 22:09   #2
Atlantic Dawn
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Price of fuel has gone up.
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20-09-2019, 09:03   #3
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Did you do a proper brimming test or are you guessing using the trip computer?
Price is not important - only litres per kilometre.
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20-09-2019, 09:32   #4
Toyotafanboi
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Agreed, go from full, to empty, to full, then report back.

Was it the high pressure fuel pump or the in tank lift pump that was replaced?

Even if you fill the tank now, you should know by the amount you put in if the gauge is reading correctly. They are a 55 litre tank so you're in the reserve now, you should be looking at approx 50 litres to brim the tank, much less than that and the gauge is reading wrong.

If you were leaking diesel you'd know, between smells and stains on the driveway.
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20-09-2019, 09:56   #5
zilog_jones
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Also: A few months back there were no schools or colleges open. If those are affecting traffic during your regular driving, it will have a significant impact on fuel consumption.
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20-09-2019, 14:20   #6
Sadb
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Quote:
Originally Posted by Atlantic Dawn View Post
Price of fuel has gone up.
No, I’ve calculated it from the actual litres put in/used.
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20-09-2019, 14:26   #7
Sadb
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Quote:
Originally Posted by biko View Post
Did you do a proper brimming test or are you guessing using the trip computer?
Price is not important - only litres per kilometre.
Not from price, I checked the actual litres I put in and checked the mileage I did.
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20-09-2019, 14:28   #8
Sadb
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Quote:
Originally Posted by Toyotafanboi View Post
Agreed, go from full, to empty, to full, then report back.

Was it the high pressure fuel pump or the in tank lift pump that was replaced?

Even if you fill the tank now, you should know by the amount you put in if the gauge is reading correctly. They are a 55 litre tank so you're in the reserve now, you should be looking at approx 50 litres to brim the tank, much less than that and the gauge is reading wrong.

If you were leaking diesel you'd know, between smells and stains on the driveway.
Thanks, it was the in tank lift pump. It doesn’t seem to be leaking now- it was leaking after the first attempt by the mechanic. But not leaking since I put in the fuel last week. I’ll fill it up and check the gauge then to see if that’s faulty.
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20-09-2019, 14:30   #9
vandriver
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I make it nearer 36 mpg.
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20-09-2019, 20:21   #10
Sadb
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I make it nearer 36 mpg.
Sorry, you are right. I was looking at a us gallon. Still very bad though!
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21-09-2019, 15:44   #11
Sam Quentin
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So this is how I do it:on the dashboard screen take note of miles remaining in tank,.let's say it's 80miles,zero your trip miles, then put 30ltrs of fuel in your car,.drive on and when the miles remaining in tank get back down to 80mls, look at your trip counter and let's say it has 300mls,. Divide 300 by 30(the 30ltrs of fuel you put in)so that's 10,.now multiply the 10 by 4.545(amount of ltrs in a gallon)the answer you get is the mpg your car just did on last fuel up..
You can also just take note of your miles and take away those miles from the new miles on your car when you get back down to 80mls remaining in tank..
I find this method pretty accurate.
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21-09-2019, 15:54   #12
my3cents
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How much fuel is left when the reserve light comes on?

If the tank was drained then the first 4-5 liters of petrol would be taken up by the reserve.
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22-09-2019, 13:03   #13
Sadb
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Originally Posted by Sam Quentin View Post
So this is how I do it:on the dashboard screen take note of miles remaining in tank,.let's say it's 80miles,zero your trip miles, then put 30ltrs of fuel in your car,.drive on and when the miles remaining in tank get back down to 80mls, look at your trip counter and let's say it has 300mls,. Divide 300 by 30(the 30ltrs of fuel you put in)so that's 10,.now multiply the 10 by 4.545(amount of ltrs in a gallon)the answer you get is the mpg your car just did on last fuel up..
You can also just take note of your miles and take away those miles from the new miles on your car when you get back down to 80mls remaining in tank..
I find this method pretty accurate.
Thanks, yes that’s how I did it. I put in 37.65 litres and got 301 miles from that which is just over 36mpg. That was with the reserve light just coming on to reserve light just coming on, so not including those roughly 5ltrs.
I filled the tank the other day now so we’ll see how this one goes.
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