Sh*tty Mileage Since Last Service
 

I recently had my '15 RS1 serviced at a local dealer, and ever since my mileage has not been up to par with what I was used to. Currently, I've got less than a 1/2 tank and I've only went 145 miles. Took a trip last weekend and got around 24mpg with mostly highway driving. I typically get 24mpg with my spirited drives around home.

Tire pressure is good. TRD intake is clean. No CELs or any indication that something is malfunctioning.

Any ideas????????? I'm at a brick wall, any help would be much appreciated.

Could be a lot of things/variables, foremost how are you calculating your mpg?

Personally I wouldn't worry about it, and it'll definitely not be due to the service.

Doubt it's due to a servicing screw up. You say you took a trip. Was this new territory? Elevation changes? Lotsa curves? I guess I am asking if you drove in a more spirited manner during this trip? Hit that loud pedal a lot?

They may have disconnected the battery reset the ECU and it is re learning. If your mileage doesn't come back to normal soon you may want to get it checked out.

Yes, give the ECU time to get brighter. ;-)

Wait, is 24-25 mpg not average? It's what I get.

DC the battery for like 2min. Then turn car on, idle for like 5min, then go drive for like 20-40 hwy miles at 60mph and youll see that itll be almost 40 (36+) mpg.

Then drive it like that for a few weeks, then drive it however you want. It'll eventually get lower with your avg though.

IMO, like posters above stated, it could be many things. For example:

I. Using 93 OCT will give me about 2-4 better mpg in highway, not sure city.
II. Car weight will impact mpg, so lose weight!
III. Cruise control is your friend
IV. wait about 100 miles after a tune up so ecu and engine goes back to its old self
V. Rarely brake when possible and keep a light foot!
VI. Sometimes, i've noticed my car runs better when in low pressure, altitude and sea level.

BTW OP, 145/6.5 (1/2 tank)= 24 mpg rounded up. That's about right for spirited. I am averaging 29mpg myself but I drive like a grandma and mixed with city.

Car mpg avg is not accurate. Either +5/-5 mpg ime.

Lastly, Twins are not a mpg machine. That's our lost cousin the Corolla or Camry.

I drive around without the spare tire....does that count :rolleyes:

I get 24 commuting on city streets
I get 34 highway hypermiling
I get 10 on the track

Some of these 'omg mpg' posters would probably say my car is broken.

It depends entirely on your driving circumstances, I wouldn't worry OP, you've checked everything you can according to the information provided, maybe you sat at more red lights than usual, maybe you did the trip at 85 instead of 65, too many variables to assess. You seem level headed, I'd search around the car for a rag leftover flapping in the breeze or blocking something and call it a day, doubt it's anything you couldn't detect. Also check your pressures with a real gauge, the light doesn't mean shit you could be at 28 psi or 48 psi in my experience without tripping the light. A 20psi swing could give you the fuel economy you're experiencing.
:burnrubber:

I'm sure it will! By .00001 mpg

The exact same thing happened to me. I was consistently getting 31 mpg on the highway. Took it in for the 37.5K mile service, and it dropped to 25 mpg. Over the last 7.5K miles it has slowly inched back up and settled around 29, which is okay because the speed limits are higher in Texas, and I've sped up accordingly.

I figured it was either the tire rotation or a computer reset. I just had the 45K mile service and haven't burned through an entire tank yet, so I'll be interested to see if it happens again.

ETA: Just to be clear, I'm not talking about the average shown on the dash. That number is bullshit. I'm talking about actual mpg as calculated for each tank based on miles driven and fuel burned.

Because 98% of my miles are highway with cruise set at 75 my MPG display has been sitting at 32 MPG since 2 weeks after I got the car. The calculated average has not waivered from 30. The rare occasions I play are so grossly over weighted by my long commutes they have virtually no effect in my average.

Maybe type of gas? This is not "my gas is better than yours" thread jack. I've noticed I get a few more mpg's out of Chevron 91 octane over the other types. I'm in CA so it's all crap. I never use the stock mpg calculator. I drive 220 miles/per day so this is something that I do keep track of daily. Maybe for shits n giggles I will fill up with all the different major brands to see if there really is a difference between fuel makes when it comes to mpg in an FR-S here in CA since I make the same drive 5 times a week.

Really appreciate all the feedback. Talked to the dealer and it looks like I'm just gonna drive it for a few more weeks. Hopefully it either corrects itself or a real problem surfaces.


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