Quoted MPG - how accurate is it?

Imperial

Full Member
Jan 10, 2006
121
7
In the first week of my new 64 plate1.4 Tsi FR. I only bought it due to the balance of MPG and 'nippiness'. My old car had a quoted average mpg of 64, the FR was quoted as an average of 60mpg. I could live with that drop. I actually used to get around 68-70mpg out of my old one, but for the same journey's I'm now only getting a quoted 55mpg out of the FR. I'm probably having to be even more careful with the FR to get it do that. I'm hoping the computer is wrong otherwise I might have made a mistake.:cry:
 

dan103

Active Member
Sep 18, 2017
112
21
55mpg out of the tsi it not to be sniffed at. My act fr averages between 45-50 mpg. mines no where near quoted.
 

Pew.

Active Member
Mar 23, 2012
1,451
142
Scotland
Manufacturer figures are done in "ideal circumstances" , which you'll rarely or ever get in real life.

They are a guide only, you can get more than their figures, you can get less.
 

Imperial

Full Member
Jan 10, 2006
121
7
Manufacturer figures are done in "ideal circumstances" , which you'll rarely or ever get in real life.

They are a guide only, you can get more than their figures, you can get less.

I realise that, which is why I was comparing 'average' figures before and after. Previously I could get better than the average figure quoted, now I'm getting worse than the average figure quoted for the same journey. Feels like more VAG miss-selling to me.
 

dan103

Active Member
Sep 18, 2017
112
21
I think its rare occurrence to get more than quoted. What was old car out of interest ?
 

Imperial

Full Member
Jan 10, 2006
121
7
I think its rare occurrence to get more than quoted. What was old car out of interest ?
Arosa tdi. Couldn't decide whether to stick with diesel or come back to petrol. Think I may have made the wrong choice!:redface:

It is a much nicer place to be compared to the arosa though.
 

dan103

Active Member
Sep 18, 2017
112
21
not sure what you were expecting going from a diesel to petrol. being 5mpg out on quoted figure isnt bad on a petrol.

if losing out of 5mpg is the wrong decision i would stick with diesel. As above have said all brochure figures and quoted are under ideal conditions or conditions that make the quoted figure the best. take mpg with a pinch of salt. I have never had one car that met its quoted mpg (All petrol)

As above honest john link is bang on for mine.
 

Imperial

Full Member
Jan 10, 2006
121
7
not sure what you were expecting going from a diesel to petrol. being 5mpg out on quoted figure isnt bad on a petrol.

if losing out of 5mpg is the wrong decision i would stick with diesel. As above have said all brochure figures and quoted are under ideal conditions or conditions that make the quoted figure the best. take mpg with a pinch of salt. I have never had one car that met its quoted mpg (All petrol)

As above honest john link is bang on for mine.


I was expecting to be within 4mpg of what I got in the arosa, certainly closer than 15mpg it appears it is now. And I also expected to be above the combined quoted mpg being as most of my miles are careful motorway miles. Our scirocco used to do in-excess of quoted average mpg when I used it for work. If I remember rightly my old Mk3 cupra would also on the journey I do.

It all depends on how you drive and the roads you use. My journey is consistent as I've been doing the same journey to work for 17 years (mostly motorway) in various cars. As I've said, the arosa and scirocco would achieve in-excess of the combined quoted mpg figure. I didn't think it was unreasonable to expect the FR to do the same. Is it?
 

KXL

KXL
Dec 15, 2016
1,581
197
London, UK
As the others have mentioned, quoted figures are done on a car 'treadmill' @ ideal temp, ideal wind (with fan) and ideal tyre PSI for max mpg. Plus also, no traffic! Plus all exercise buffs (like myself) know that running on a treadmill is way easier than running on the pavement/park, due to gradient, wind, surface etc. However what I can say is from experience, the previous generation cars quoted mpg was more accurate of real world driving, as manufacturers back then weren't as pressured to reduce CO2 + increase mpg figures.

Saying that....I would say it is very possible to achieve the figures (difficult, but it can be done) in the real word (if) when there is no traffic. Early on Sun AM or in the middle of the night. My 1.0 EcoTSI official figures are 53/64/72. When there is little or no traffic, 50+ mpg possible (once even did close to 60 in city), and combined of 64 too! See attached!

What you say is true though, it's easier to do the mpg in a diesel. My old Leon 2.0TDI DSG, 55/64/70 official mpg figures, i could easily get close to 60mpg without really trying on highways, and routinely got 64mpg on 40-50mph roads. On the petrol, i really needed to try hard to get close to official figures. I would say if drivers could hit the 'city' figures with their 'mixed' driving, this is already very good, as there is usually traffic, and traffic (esp crawling) kills mpg.

Out of curiosity @Imperial...assuming yours is 1.4 EcoTSI (ACT) and comes as standard the 17 inch 40 profile Tagus rims? Also all my mpg figures are with Shell Vpower 99 RON. Like for like they gave me 3-4 more mpg all things equal compared to Shell/Esso 95 (or so the trip computer says)
 

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dan103

Active Member
Sep 18, 2017
112
21
I think it is unreasonable to assume every car your going to buy will achieve in excess of their quoted fuel consumption.

If you have worked out your mpg manually and its a deal breaker as said above sell up and get something else otherwise drive like a granny to get those extra 5 mpg. end.:drive1:
 

camelspyyder

2 SEAT-er
Jun 26, 2014
1,305
175
In the first week of my new 64 plate1.4 Tsi FR. I only bought it due to the balance of MPG and 'nippiness'. My old car had a quoted average mpg of 64, the FR was quoted as an average of 60mpg. I could live with that drop. I actually used to get around 68-70mpg out of my old one, but for the same journey's I'm now only getting a quoted 55mpg out of the FR. I'm probably having to be even more careful with the FR to get it do that. I'm hoping the computer is wrong otherwise I might have made a mistake.:cry:

Most of the SEAT fuel computers I've had are 6-10% optimistic, so it's possibly even worse than you think. You need to do a few brim to brim runs and work it out.

Small petrol turbo's are wildly over quoted on mpg by the manufacturers. My 1.2 TSI could never get within 5 (and normally 8-10) mpg of the factory overall figure, even with AC off and driving like a nun. My 1.0TSI is even worse. Whereas my last 2 older diesels - the FIAT JTD was always spot on the EU figure and the older mechanically injected Mitsubishi actually beat it by 8-10mpg.
 
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Imperial

Full Member
Jan 10, 2006
121
7
I think it is unreasonable to assume every car your going to buy will achieve in excess of their quoted fuel consumption.

If you have worked out your mpg manually and its a deal breaker as said above sell up and get something else otherwise drive like a granny to get those extra 5 mpg. end.:drive1:
Well u r entitled to your opinion, but I disagree. It is reasonable to expect 2 different cars driven in the same way on the same route to achieve the same % performance v's manufacturers figures. Out of the cars ive driven this is the first one that hasn't. End. I bet you are a pleasure to be around.

Thanks to the others who have managed to offer some explanation though on the possible reasons. I'll see how it goes over the next few weeks and maybe try some super unleaded.
 

dan103

Active Member
Sep 18, 2017
112
21
Well u r entitled to your opinion, but I disagree. It is reasonable to expect 2 different cars driven in the same way on the same route to achieve the same % performance v's manufacturers figures. Out of the cars ive driven this is the first one that hasn't. End. I bet you are a pleasure to be around.

Thanks to the others who have managed to offer some explanation though on the possible reasons. I'll see how it goes over the next few weeks and maybe try some super unleaded.

You said the above " the arosa and scirocco would achieve in-excess of the combined quoted mpg figure. I didn't think it was unreasonable to expect the FR to do the same. Is it? "

not "It is reasonable to expect 2 different cars driven in the same way on the same route to achieve the same % performance v's manufacturers figures"

Hence my response its unreasonable to expect every car to achieve greater than the quoted but yes i agree based on same journey driven the same way % performance vs manufacturer guide can possibly be achieved across the board.

I am thanks very much. :cheeky:
 

camelspyyder

2 SEAT-er
Jun 26, 2014
1,305
175
Well u r entitled to your opinion, but I disagree. It is reasonable to expect 2 different cars driven in the same way on the same route to achieve the same % performance v's manufacturers figures. Out of the cars ive driven this is the first one that hasn't. End. I bet you are a pleasure to be around.

Thanks to the others who have managed to offer some explanation though on the possible reasons. I'll see how it goes over the next few weeks and maybe try some super unleaded.

Super unleaded in the 1.2 gave me 6% more mpg - but at a 9% greater cost :(
 

KXL

KXL
Dec 15, 2016
1,581
197
London, UK
Super unleaded in the 1.2 gave me 6% more mpg - but at a 9% greater cost :(

That's right, but manufacturers when doing official mpg / Co2 tests will do whatever it takes (although, dieselgate showed this is exactly the case) to push mpg as far as possible and CO2 as low as possible to put on their specifications. Wonder if non-Turbo cars are more accurate in mpg figures what you could realistically get in real world when compared with on paper mpg.
 

Imperial

Full Member
Jan 10, 2006
121
7
Just filled up. Had 57mpg indicated but 52.5mpg actual. I know most would be happy but I'm disappointed. It's about 10 less than I was hoping for. Filled up with super to try that but I can't see it being worth it. Might be a short lived ownership this.:doh:
 

camelspyyder

2 SEAT-er
Jun 26, 2014
1,305
175
I've just coaxed mine to a genuine 50 average, but I can't see it ever bettering that.
Certainly not going to get the EU 65+ overall figure, but EU figures have moved further and further from reality over the last 30years.
Years ago I drove a super lightweight diesel like your last car. it did 60+mpg on the commute and still over 50mpg on the every weekend 800 mile trip at 90mph. Modern petrols can't do that.
Not impressed with your 9 % error on the dash readout either.
 
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