Wow. Some interesting maths on mpg

[golfmk4owner]

Hi guys. I have checked loads of mpg threads, but my question is a bit different in the way that i've got some different facts to play with. I'm getting so annoyed at my findings that i've decided to be very sarcastic in order to humour myself to avoid  driving off a cliff.

My dilemma: I want a mk5 GTI but am unsure how much extra fuel will cost me. I'm getting a bit more annoyed because people say "drive a tdi how you want and still get 50mpg". Well, that's what i thought but look at this...

Here's where it gets interesting. People say they can get 300 miles to a tank in a GTI. I only get 400ish in my GT TDI (140). Bare in mind by "full tank" i mean until the fuel light comes on.

But check this out...
My last fillup I reset my trip and mpg stats. My light came on at 408 miles. Now after checking my handbook it says when the light comes on there is 7 litres of fuel left. So, 55 litre tank minus the 7 litres left means i used 48 litres of diesel.

48 litres is 10.6 gallons (48/4.5 = 10.6)
this equals 38mpg       (408/10.6 = 38.4)

BUT here's the part that really annoys me... My display readout said that for that tank of fuel my AVERAGE was 54MPG! As you can clearly see, i just worked out my average, and no way was it near that! Can it really be that inaccurate? Because i've just PROVED my mpg.

So i'm thinking a few things... What should a GT TDI get, on average, with mixed driving, to the light?
Secondly, if mine is very low, what might cause this?
But mostly, i'm thinking if this is what i can expect, have i got much to lose by going to a GTI?

Your thoughts please, and if you're going to give me figures, please don't give me figures from your computer readout, because frankly it's a load of sh!te. GTI miles from full to light would be appreciated!

[Rhyso]

What sort of journeys are you doing?? Short, stop start journeys and diesels will struggle to get decent MPG

If its mainly motorway then id check your tracking and tyre pressures to start with. Then lok at the engine side of things. The biggest culprit is the MAF sensor. Equally if your car has done a highish mileage id clean out your EGR valve

[golfmk4owner]

Well on that particular tank i did a fair bit (about half) of motorway driving! Why do diesels struggle for mpg in cities then?
But more to the point, even if i can get better by cleaning egr etc, why is my computer still saying 54mpg?! Absolutely nowhere near!

[Hurdy]

The best way to be accurate with a MPG check is use the trip computer for the mileage only and reset it every time you fill up. Keep the receipt and check the mileage against the fuel you have just put in to top it back up again. Simples.

With a Modified Golf R - 1500kg and AWD, I don't look at the miles per gallon as it would make me wince - I'm out for Smiles per gallon

[Rhyso]

Diesels struggle as they take longer to warm up and thus are less efficient until they do so

A 140 should see an easy 450+ miles to a tank 

[dTEA]

As said in previous threads I used to get 300+ but I never ran it from full to empty light. That's mixed driving.

In the new un then I get between 240-270 but again I'm having fun and I do think the DSG box makes a difference. If you are worried about fuel and do motorway driving I'd personally stay with the TDI. Depends on why YOU want one...as Hurdy said Smiles per Tank

[golfmk4owner]

The best way to be accurate with a MPG check is use the trip computer for the mileage only and reset it every time you fill up. Keep the receipt and check the mileage against the fuel you have just put in to top it back up again. Simples.

As i said in my post, thats exactly what i did. It worked out at 38mpg. It's all very well saying you wont get as good until theyre warm etc, but even so that's nowhere near what people say they get at a minimum, and AGAIN why is the computer telling me that that tankfull averaged 54 when i workout it out and proved it was 38?

[JC]

jesus, I get more than that in my lardy vectra cdti, and I rarely get to see 6th gear on my daily commute 

did managed 72mpg on the way to Germany  though 

[golfmk4owner]

jesus, I get more than that in my lardy vectra cdti, and I rarely get to see 6th gear on my daily commute 

did managed 72mpg on the way to Germany  though 

Lol. But was any of that calculated mileage though mate? Because to be honest now, any figure that anybody tells me they get I wont believe unless it's calculated. Those computer readouts are utter sh*t i have learned.

[JC]

i have kept a comprehensive record on a spreadsheet  since i owned the car. over 22k

 Always fill it up, then reset, and record it. just dont work out how many gallons you have used, then how much you have spent on fuel 

worst tank full was 41.8mpg

best was 57.1 but that included some spirited driving in germany after a long slow drag down there