Issues with 2015 WRX gas mileage

2576 Views 5 Replies 5 Participants Last post by yethi, Oct 21, 2017

Blue Rex 15

Discussion Starter · Oct 17, 2017

Hello everyone. First time Subaru owner here. I just picked up a 2015 WRX last week and so far am loving it. I had a question though. Gas mileage lists 21 in city and 28 highway, with a 15.9 gallon tank. I filled up my tank with 93 Octane Shell V-Power and reset my Trip A and got just over 250 miles on a tank. That's just under 16 MPG. Seems really low. Also, I let my tank run until the fuel light came on then probably drive another 15 miles or so before I filled up, and when I did, the car took just under 14.5 gallons. Should I have anything checked to see why I'm losing fuel economy or is this normal?

I posted in the Subaru sub-Reddit and got some suggestions but nothing for certain so I thought I'd try here since it's more specialized to my actual car. I was told to check O2 sensors, try blasting out the fuel injectors, possible bad aftermarket ECU flash from the previous owner, etc. I'm on my second tank of gas now (same type of gas, different filling station), so we'll see how it goes, but I have a feeling it will probably end up the same. Anyone else know what might be causing this or what would be the first (and cheapest) things to check?

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JaySin

· #2 · Oct 17, 2017

First, before jumping into the trouble shooting, maybe try using Fuelly.com and/or their smartphone app and use it to track your next 3-4 fill-ups and see what it calculates out for you. The reading on the interior gauge is about 10% generous, FWIW. I drive all city and use Shell as well. I'm avg 20.8 mpg over almost two years.
I wouldn't jump to conclusions quite yet. Maybe it was sitting there awhile before you bought it. Maybe there were some crazy people test driving it. Lots of factors.

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Blue Rex 15

Discussion Starter · #3 · Oct 17, 2017

I'll have to download the app and see. The car is a 1-owner vehicle and was only sitting on the lot for probably 3 days or so before I went there. I was the only person to test drive the car as I put a down payment on it and they put it inside of their shop until the next couple of days later after that when I went to pick up the car and give it a look over before closing the deal on it. Just seems like with everyone else citing 20MPG or more in the city and I'm getting sub-16, something would be going on. I have experienced any of the rev-hang that other people said was a problem with these so that's what led me and a few others I asked to thinking it might be a weird ECU flash. I will have to try the app though. Have been driving the car very conservatively this tank and not getting on it at all to see how much, if any, difference it will make.

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Firefighterjake

· #4 · Oct 17, 2017

I usually figure on around 325-350 miles before needing a fill up . . . while I don't hand calculate or use Fuelly I typically get around 30 or 32 mpg according to the car computer which I know is a little optimistic, but definitely not as little as 16 mpg though. Something doesn't sound right.

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XJman

· #5 · Oct 17, 2017

Without knowing your driving habits I can only take stabs. Try a lighter foot. If that doesn't help look at possible boost or vacuum leaks.

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yethi

· #6 · Oct 21, 2017

Blue Rex 15 said:
Hello everyone. First time Subaru owner here. I just picked up a 2015 WRX last week and so far am loving it. I had a question though. Gas mileage lists 21 in city and 28 highway, with a 15.9 gallon tank. I filled up my tank with 93 Octane Shell V-Power and reset my Trip A and got just over 250 miles on a tank. That's just under 16 MPG. Seems really low. Also, I let my tank run until the fuel light came on then probably drive another 15 miles or so before I filled up, and when I did, the car took just under 14.5 gallons. Should I have anything checked to see why I'm losing fuel economy or is this normal?

I posted in the Subaru sub-Reddit and got some suggestions but nothing for certain so I thought I'd try here since it's more specialized to my actual car. I was told to check O2 sensors, try blasting out the fuel injectors, possible bad aftermarket ECU flash from the previous owner, etc. I'm on my second tank of gas now (same type of gas, different filling station), so we'll see how it goes, but I have a feeling it will probably end up the same. Anyone else know what might be causing this or what would be the first (and cheapest) things to check?

I have a pretty even mix of aggressive driving, City and highway. I still have never gotten less than 280 miles for a 14 gallon fill up. That's the least mpgs i got for a tank (20mpg) I usually average 22 and the computer shows 24.

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