Large Drop in MPG all of the sudden, help!

[Unexplainedbacon]

Hi All,

2012 bone stock GTI with 82k miles was averaging 27mpg per tank, last two tanks I've gotten 22mpg. No change in traffic, driving habits, or any other factor I can recall. What could possibly account for such a substantial decrease?

 

[SoWalGTI]

82k. Ever have a carbon cleaning performed? I'd say your due. Did you change your fuel filter at the recommended intervals as well?

 

[GTIinthree]

I just had a drop in my average as well but not as dramatic. I was averaging 24-25 mixed driving and when I got a tank that I only got 21 I assumed it was because my HPFP went out and they dumped some fuel. The next two tanks after that were 21. I drove her harder for a tank and she bumped up to 23 but then the last two tanks were back to 21. I checked my Fuelly for this time last year and I was running around 25 on average.

I only have 33K so I highly doubt it's carbon buildup. I do have some short trips around town but I still drive 15 miles to work each way three times a week averaging 65-75.

Sorry to hijack but thought I would throw mine on here too incase more people are having this issue. If it's an issue I'll delete my post.

 

[damagi123]

im at 59k and my avg mpg has went from 27 to 21 as well. it happened about 6 months ago but it literally happened overnight

 

[sterkrazzy]

Just like others...I used to be able to get 28-32 mpg on the way to work regularly and then one day for no apparent reason it dropped down to like 23-24 mpg and it was like that for a while. I have no idea if it was something I did to the car to fix it, but eventually I started getting my normal mpgs again.

 

[lilonespaz]

How do you all get this mileage? Ive only ever gotten like 20-22mpg

 

[sterkrazzy]

How do you all get this mileage? Ive only ever gotten like 20-22mpg

You drive with the ac off? I don't really like how the car drives with AC on and it kills my mileage. On the same drive with AC on I only get like 24-25 mpg, but turn the ac off and I can get 28-32 every time. Plus I like to drive with the windows down, so I just keep the AC off all the time. Even when its 100 degrees outside, I don't mind it.

 

[Tjbell]

Max a/c in the summer, I get 27 combined. mostly 2 lane 50 mph, on the ride home its all traffic. 27 miles each way.
I randomly get 22 ish but I cant figure out why, I don't drive any different, and I have tracked the fuel economy over the last 8k miles

 

[dbizzle22]

MPG is so YMMV. Tire brand/model/remaining treadwear, alignment status, highway or streets, traffic during those drives, how heavy your right foot is, incline and decline in roads you drive, ambient temps, etc etc.

If everything really is exactly the same, then look at tune ups like tire condition, spark plugs, air filter, gas quality (don't they give out different types depending on time of year?). That type of thing.

 

[lilonespaz]

You drive with the ac off? I don't really like how the car drives with AC on and it kills my mileage. On the same drive with AC on I only get like 24-25 mpg, but turn the ac off and I can get 28-32 every time. Plus I like to drive with the windows down, so I just keep the AC off all the time. Even when its 100 degrees outside, I don't mind it.

Yeah i ride with the ac on about 3/4 of the year. I live in Florida its 95+ for most of the year lol and humidity is like 80% or more for half the year. the other half is like 65% or higher. We dont have really dry air.

 

[U-20T]

27mpg highway with A/C last night and this is 255 sticky tires, dsg and awd.

 

[sterkrazzy]

Yeah i ride with the ac on about 3/4 of the year. I live in Florida its 95+ for most of the year lol and humidity is like 80% or more for half the year. the other half is like 65% or higher. We dont have really dry air.

Man up!! I'm in SWFL

 

[PenguinGTI]

I have a APR CAI, the filter is covering under a carbon fiber box. I won't able to see dust built up until. After 15k miles, mpg down to 26 on highway, after I clean the intake filter, mpg up to 30 on highway.

Guys in this forum just helped me on engine vibration. I tried to help. Not 100% sure.


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[damagi123]

I have a APR CAI, the filter is covering under a carbon fiber box. I won't able to see dust built up until. After 15k miles, mpg down to 26 on highway, after I clean the intake filter, mpg up to 30 on highway.

thats totally worthwhile advice. ill clean my filter and see what happens

 

[Injen1us]

It's already been addressed all the factors that go into mileage.... but one no one talks about is braking. I basically try not to ever brake. Rev match and downshift is much more efficient. I try not to slow down if on a freeway or highway. Everytime you brake you have to recover that speed.

Doubt this is op's problem but it is worth mentioning