why am i getting such crap MPG lately?

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m8arx

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my AMK S3 usually gets 25-26mpg average but in the last week it's plummeted to 20-21mpg

i haven't changed my driving style/habits, i never go above 3.5k, always drive slowly and smoothly, using the same petrol station i always do.

what the hell is going on?

before anyone suggests it, i dont have vagcom to log/monitor anything with.
 
Without Vag com you can only guess and replace parts randomy, or find someone close to you with it that can scan your car but to me it sounds like its our mass air flow meter, im no expert on fault finding so you would definatly need this checked.
 
without logging the car on vag-com your not really going to find weather theres a fault or not, but could be maf maybe lamba sensor, temp sensor
 
the MAF on the car is only 5 months old mate - hope to hell it's not this.
 
was the maf a genuine one as afew people have gone through maf's quite quickly
 
Thermostat?
Does your temp reach 90 quickly and stay there?

My car used to do 25-26mpg, now on 21.7. Temp hovering at 80 most of the time.
Might replace the stat at the weekend unless there's an Aberdeen ASNer with Vagcom willing to help me out?
 
JS - no, it heats up slowly as normal, same as it always has.

i've not noticed anything different in the way it drives at all.

the cold weather is interesting, but i don't ever drive the car fast.....it's got to be the slowest driven s3 in the uk lol
 
Cold weather situations will always use more fuel and needs more as it takes longer to heat up but once up to temp should return normal mpg but overall will use more fuel in winter.
 
my mate has a leon cupra r and he's averaging 29mpg even in this weather and he drives his full chat a lot of the time - so i'm not sure about the cold weather having THAT much of an effect.
 
A few possibilities to consider, colder weather, heater on longer, ditto heated seats, wipers. Clocks moved forward so headlights used longer.
Sensor faults, have you done the math with a topped up tank to see what your actual use was?
 
heaters aren't on any longer than they normally are. don't have heated seats. wipers haven't been used because it's been dry for weeks up here. i work 8.30 - 5 and live a 5 minute drive from home so the lights are on for a maximum of 5 minutes at night.

not done a full tank but the computer is usually spot on.
 
^^^ you said it warms up slowly, should be at 90 within 5-10 mins really how long does it take?
 
aye it takes about 5 minutes to get to 90 and stays. it takes me 5 minutes to drive to and from work and by that time it's heated up and sitting at 90.
 
My un-mapped AMK S3 usually returns 32-33mpg on the DIS with my normal 32mile round trip to the golf club at weekends, but in winter this drops to ~31, as it has the last month or so. Usually I'll get ~36-37mpg on a journey up to the Lake District @72mph on cruise, but the other week only reached 34mpg, so I guess the cold weather does indeed affect it.

Cheers,
 
AudiS3-Turbo said:
29mpg at full chat allot of the time.....hmmm,clearly something wrong with mine then.
Click to expand...

hard to believe mate in my car if i floor it everywhere i get like 19 mpg even before remap it was about 23mpg


mine has been droppping recently but like others put it down to cold weather.
 
well the cold weather can suck my plums. betting a loan of a launchmaster in a day or 2 so will plug it in and see what the score is
 
My MPG goes down in the cold weather. However this tends to correlate directly with my foot also going down....

Cold air.... ahhhhh. Saw 0 degrees IAT on the motorway this morning.... :thumbsup:

Also I am still returning 26.4 MPG average, and I have a VERY heavy foot.
 
Breezey said:
^^^ you said it warms up slowly, should be at 90 within 5-10 mins really how long does it take?
Click to expand...

My car seems to take forever to heat up, I let it tick over until the the revs die to normal idle then I drive it. Sometimes I can be driving 20mins before it's warm.
My car is unmapped. Just has milltek turbo back and cai, I struggle to get Anything over 22-23 mpg around town. And that's a 150 1.8t a3!

Would the stat cause this?

Jordan
 
Last edited:
denser cold air winter so in theory shouldn't be over fueling to compensate.

if you have access to vagcom carry out logs on the maf airflow and check lambda function. clean & readapt the throttle body.

also look for any perished pipes around the engine bay.

change oil, air filter, plugs, if its due
 
Jordan1.8t said:
My car seems to take forever to heat up, I let it tick over until the the revs die to normal idle then I drive it. Sometimes I can be driving 20mins before it's warm.
My car is unmapped. Just has milltek turbo back and cai, I struggle to get Anything over 22-23 mpg.

Would the stat cause this?

Jordan
Click to expand...

Could be a contributing factor yes. I am loath to say it would be the entire cause, as split vac hoses normally feature too.
 
The air is colder, denser, so the car should need less fuel then in the summer, when its thiner.
Have you looked at the simple things, like filters?
when was its last service?
 
cookstein - i've always wanted one and owning an s3 isn't all about speed because lets be fair compared to a lot of cars these days they're not the quickest....but i love the look and comfort of them hence why i got one :)

i do occassionally give it a boot but i leave it to the motorway on a rare occasion, never around town.

i simply can't understand why the cold weather could have a 5-6 mpg difference......there must be something underlying causing the issue. i'll see what i can see on the launchmaster.
 
doing some reading about Cold air VS MPG.
It appears that the advatages of the denser air (containing more oxygen) is out weighed by the denser air creating more drag on the cars body, longer for the car to get to temp and the fact that electric items will need to be running for longer and possibly hardder than in the summer.

There is evidence that the altornator effects MPG of a car depending on how much current is needed.
all lights, heaters, wipers, fans, seats and so on, switched on will put more resistance on the altornator which will in turn effect the MPG on the car.

All theses factors added to a possible dirty air filter (for example) could cause the MPG that your seeing.

Here is some more reading if your interested.
 
cheers axios but i've already stated that the lights are on for 5 minutes max every day, don't have heated seats, the heaters are not on any more than normal, and the wipers haven't been used for weeks as it's been dry up here.

going to take it a drive tomorrow on the motorway for a while and see what i get and if it increases then i'll stop worrying, if it doesn't increase then i'll get it plugged in on monday.
 
that fair enough mate, it is a very good looking car, but still had to ask :)

My first though would have been the thermostat, when stat broke my mpg dropped by about 4 mpg. But you say your car heats up normally...

My DIS average MPG is currently siiting at 26.4, bit too low for my liking. It used to be around 29-30 when i first bought the car a couple of years ago
 
m8arx said:
cheers axios but i've already stated that the lights are on for 5 minutes max every day, don't have heated seats, the heaters are not on any more than normal, and the wipers haven't been used for weeks as it's been dry up here.

going to take it a drive tomorrow on the motorway for a while and see what i get and if it increases then i'll stop worrying, if it doesn't increase then i'll get it plugged in on monday.
Click to expand...

Not a problem.
I was just using the heated seats and so on, as an example.

I'm stumpted for ideas apart from checking the simple/free things first and then working your way up.

If there is a fault, it be interesting to see what it is. :)
 
yeah cheers for all the advice guys - i'll definately update this thread once i've had it scannedand found the culprit :)

i have just thought of something though - my temperature gets to 90 by the time i get to work from the house or vice versa, which has always been the case, but i popped the bonnet this morning and the inlet and turbo pipe where still fairly cold but i don't know if this is down to me simply not booting therefore the heat from the turbo isn't heating up the pipes/engine bay in general as much as it shouldd do?
 
how far is your drive to work? If you drive below 3.5K rpm then i wouldnt have thought your turbo was doing much work so prob wouldnt heat up too much
 
yeah cool thought that - it is no more than a 5-7 minute drive depending on traffic. i live 2 miles from work.
 
well, you will never get a good mpg average if your all your journeys are short cold ones. But, still doesn't explain why its dropped recently. Maybe it is just the cold weather
 
yeah i understand that and it's always been no lower than 25.8/9, but this is a massive drop.

i'll see what happens over the weekend
 
Well mine is an AMK and i dont think i ever get over an average of 21mpg unless i'm on a decent run, normally the usual commute of 5 mile each way in stop start traffic gets me 21mpg, i thought it was the norm, or could something on the car be toasted?
 
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