Fuel Mileage Dropped Significantly after Dealer Maintenance - Subaru Crosstrek

Hi all,

Long story short I brought my 2013 Subaru Crosstrek into the dealer for a standard 30k maintenance and since getting it back I’ve had a significant drop in MPG’s. From 27-29 down to 21-23. They are trying to tell me its just because it’s winter, but I’ve had the car for two years - same work, apartment and parking situation, and never had this bad mileage. I bought the car in January 2013, and we had the worst Minnesota winter during 2013-2014 and I still managed 27-28ish mpg then. I think its something they did during the service but they can’t replicate the problem on their end.

Long story long:
30k maintenance included:

Replace filter with Genuine Subaru oil filter
Check and top off all fluids
Rotate tires and set tire pressures
Replace cabin air filter
Replace Spark Plugs (if applicable)
Replace Air Filter
Inspect Brake Pads and entire Braking system
Replace Brake Fluid
Check Axle Boots and Shafts (front & rear)
Check operation of clutch system (if applicable)
Inspect Steering and Suspension systems
Inspect Cooling system/Replace Engine Coolant as needed
Inspect Camshaft Drive Belt (if applicable)
Inspect Wiper Blade condition
Inspect Fuel lines and system operation
Inspect and Top Off Differential (front & rear)
Inspect and Top Off Transmission Fluid
Complete Multi-point inspection
Free car wash

They additionally replaced my engine air filter which they said was dirty (hadn’t been replaced in 2 years)

Here’s all my observations:
Ever since I got the car back, January 2nd, 2015, my MPG on the digital readout went form hovering between 27-29 down to 21-23, sometimes 18 and the highest is the upper 24’s. I brought it back into have them check it 3 times now. I live in Minnesota, every time they tell me, “it’s the cold weather, you cant expect better milage in cold weather”

1st time (Early February 2015): They diagnosed a sound in the transmission and replaced the entire transmission.
2nd time (End February 2015): They did a fuel consumption test and somehow managed 33mpgs as opposed to my consistent 21mpg. I think it may have to do with them starting it from a warm garage rather than cold starts (real world conditions I’ve had for two years)
3rd time (Today, March 1st): I noticed fuel gauge didn’t fill to full when I got it back, and intermittently will show a notch or even a quarter tank missing even though I know the tank is full. They couldn’t replicate that problem either today (intermittent) and are now refusing to diagnose my car further.

I’ve had the car two years now and never had mileage this low. I bought it in January 2013, and last year we had the coldest weather in a long time and I was still getting in around 28mpg. This can’t be the issue.

I asked them to check the MAF sensor, the air filter, and now the sending unit, and I have no idea whether they did any of that. I’m assuming not because check-engine light wasn’t on and they don’t want to be told what to check. The only reason I can find that they got 33mpgs during their fuel consumption test is that they start the car warm from a heated garage, and then parked in a garage over night - I never had heated parking in two years in Minnesota so there’s something new that is going wrong since the 30k maintenance that is affected by cold vs warm start.

Any thoughts at all as to how to proceed? They don’t want to do further trouble shooting and are assuming it’s my driving habits or the cold weather. I want to take it to a competing dealer for a 2nd opinion so that it’s still under warranty for any repairs. Where should I tell them to start looking??

Despite what you think of last winter, this February has been one of the coldest in history for the eastern half of the US.

My suggestion is to fill the car and put some highway miles on it. Refill and do the math on miles traveled vs gallons needed.

I wouldn’t put too much faith into a dashboard readout as those can sometimes go stupid. The ones in my Lincolns have always been near dead-on but now and them they will get goofy.

A proper scan of the engine management system is a logical first step. My feeling is that if your fuel mileage has really tanked by that much the CEL should be illuminated and there should be codes set due to rich running.

Low tire pressure can cause loss of fuel mileage but if that were the case the TPMS should be alerting you of it.
I have no idea how the dealer checked the mileage and came up with 33. That could be a line of BS or the truth.

The fact that the fuel gauge is reading incorrectly may be the cause of the appeared mileage drop.

The MPG displayed is based on an algorithm program.

An algorithm program is a self-contained step-by-step set of operations to be performed. Algorithm programs take in data information from different sensors and then make calculations based on the information from those sensors.

If any of the sensors, such as the fuel level sensor sends an erroneous signal to the algorithm program, the program will make a miscalculation.

I’d ask the dealer to find out why the fuel gauge isn’t reading correctly.


@Keith - we had 67 days below 0 between december and February 2014 last winter (Twin Cities MN), so I was just saying ultra cold weather vs this winter isn’t new. We had that polar vortex sitting on us last year :slight_smile:

@ok4450 I did track manually as well, and it matched up a little under the digital meter: first full tank I tracked =287.9 miles on 13.929 gallons = 20.67 mpg (at least 80 miles were highway in one day when I criss-crossed the metro area) Smaller range was 57.9 miles on 2.917 gallons = 19.849 mpgs

They weren’t seeing CEL’s which is part of the problem. The digital readout DID show 33mpgs when I got it back that 2nd time, I believe they are telling the truth. I think they drove it under warm startup conditions to get that though. For two years I’ve started in bare cold and was able to get 28, not 21, that’s my issue.

Also, I’m not sure if the fuel gauge not operating correctly is part of the problem or a different problem altogether. When I filled it to full, the meter was stuck on a little over 3/4 (put more than 2 gallons go in so it should have moved up to full) This was an issue they couldn’t replicate either :frowning:

@tester - they couldn’t replicate the gauge problem and are refusing to continue troubleshooting stating “who is going to pay for this?” I took photos of it stuck at 3/4 but they said it’s just a photo and doesn’t prove anything. Super frustrating.

It may be the mpg display is wrong, not that you are getting lower mpg. Suggest as first course of action to figure your mpg using the standard way, fill up & reset the counter, drive until the next fill-up, the compute miles driven/gallons used. Do this 3 times before assuming the mpg has decreased.

If the above test shows you are actually getting lower mpg (unlikely in my opinion), that is usually caused by a coolant temperature problem. Either the coolant isn’t reaching full operating temp due to a faulty thermostat (unlikely in a 2013) or the engine coolant temp sensor is faulty and makes the ecm think the coolant is too cold, when it actually isn’t too cold. If the ecm thinks the coolant is colder than it is, it will inject more gas than is needed.

Are there any diagnostic codes indicating a coolant temp problem? Is the dash temp gauge showing the same temp it has always shown? ; i.e. did you use a sharpie to put a mark on the gauge when everything was warmed up and correctly working?

Hi @GeorgeSanJose , I did do a full tank rundown and then a shorter tank and measured manually, when I get the car back I’ll do another full tank.

Here’s the results: First full tank I tracked =287.9 miles on 13.929 gallons = 20.67 mpg (at least 80 miles were highway in one day when I criss-crossed the metro area) Smaller range was 57.9 miles on 2.917 gallons = 19.849 mpgs

I cant do a engine temperature check- the subaru just shows 3 blue wavy lines when temp is cold,and they go off when it’s “warm”.

I’ll make sure to mention the coolant thermostat at the next place I bring it to if my dealership doesn’t resolve tomorrow. The cooling system is something they checked during the 30k maintenance that has correlated with the start of my mileage problem. “Inspect Cooling system/Replace Engine Coolant as needed”

@slp27 I know you are frustrated and the dealer’ s personnel are too. I would suggest not showing anymore photos from your phone. Just a calm statement about your concerns even if you have to refer to notes you have made.

Replace Spark Plugs (if applicable)
Check operation of clutch system (if applicable)
Inspect Cooling system/Replace Engine Coolant as needed
Inspect Camshaft Drive Belt (if applicable)

If applicable? As needed? What did they actually do?

I don’t have access to your car’s specs, but if you have a timing belt and they changed it, they may need to recheck the cam timing. Clearly they’ve decided that you’re imagining the problems, but a vacuum check should be enough to confirm a mistiming of a camshaft. If it is mistimed, you may be experiencing poor performance as well, but it may be hiding under the poor mileage.

You’ve done a great job providing details, but see what they actually wrote down about the timing belt and post it here. If they did change it, it was really really early… but they definitely would have the charges on your copy of the shop order.

Meanwhile, if one of you guys knows whether this has a belt and if so whether it would have been changed this early, post in. I’m perfectly comfortable to be told that it doesn’t, or that they would never have changed it this early, but the answer to the question would ease my mind.

@“the same mountainbike” I don’t see anything about a timing belt:

Here’s whats on the actual invoice as things they installed/replaced or charged me for - the above was copy pasted from their website.

Major Service Interval:
Top off power steering, window washer, brake and clutch fluids, tire wear patterns and condition, adjust pressures, test front and rear lights/turn signals. Service disk brake pads, calipers and drums. I spect front and rear axle boots and axle shaft joint portions. Inspect brake lines, check operation of parking brake system. Inspect clutch and hill holder system, steering and suspension systems for wear and damage. Replace standard spark plugs. Inspect plug wires, replace air cleaner element. Replace engine coolant. Test pressuer cap. Inspect cooling system, hoses and connections. Replace automatic transmission fluid. Replace rear and front differential (gear) oil. Replace fuel filter. INspect fuel system lines and connections.

Additional Line items:
Gasket, Brake Fluid, Gear Oil, Window Wash, Filter (fuel?), Element Air (Engine air filter).

Also they replaced my entire transmission the first time I brought it in following this maintenance when I complained about fuel mileage.

It’s entirely possible the cooling system service has done something to upset the coolant temp regulation and monitoring system. Good idea to ask the shop to double check all that. It’s even possible a connector has been left disconnected or partially disconnected involving this system.

Thanks slp27. I don’t see anything on the list that might cause a drop in mileage. Sorry.

I know this sounds crazy, but are you certain the OD is engaged? I’ve seen it happen that an OD button on a Mazda was left unpushed and the vehicle owner, and elderly lady (my mom), couldn’t understand the vehicle’s change in performance.

Had my used car for 8 years last winter significant drop in mileage in the winter, had it all checked out, and all is fine, this year same thing, old or cold, running fine, blaming the cold, though 85k on the replacement 100k plugs, who knows.

@“the same mountainbike” - No, the Subaru doesn’t have an OD, just Drive and then “M” where I can do paddle shifting if I wanted to.

@GeorgeSanJose I keep doing more reading on cooling and this seems like a likely culprit. I have noticed when I have my car’s heat on 85 and it doesn’t warm up very fast, but I just attributed it to the low teen outdoor temps.

@barkydog they say all is fine for me too. I’ll see if they’re willing to check the cooling system like George suggested, but this particular location seems pretty unwilling to troubleshoot further.

Well maybe this will help, I bought my new Legacy last December. About this time last year I was getting about 31 mpg measured, 32.4 on the dash. Lately I’ve been getting around 27 measured, 29.5 on the dash. Hoping for better when things warm up.

I see nothing on the list that would affect fuel mileage negatively and assuming the driving habits have been the same the entire time I start to wonder if the fuel blend has changed and excessive cold is the cause of the lowered fuel mileage.
You might just tough it out until warmer weather and see what happens.

I understand you may be between a rock and a hard place but the dealer is also in regards to the “who pays for it” part of the equation. Even a 6 month old car with 10k miles on it doesn’t get a blank warranty check for inspection of this or that, replacement of widget A, and so on.

I worked for several Subaru dealers and SOA is notoriously chintzy about warranty reimbursements. The customer may not see this but the dealer and the mechanics do when they’re coerced into doing things for free.
This often leads to “then it ain’t gonna get done”.

I am driving 2015 wrx and have found a significant decrease in fuel mileage this winter in Maryland (third coldest February on record here). I have also found that the onboard fuel consumption reading is “optimistic” and that the engine takes an inordinately long time to reach optimal operating temperature. My background is working for a major German auto manufacturer dealership and have observed over the years that the German brand that I work with reaches full operating temperature in a very short span. Colder engine temperatures lead to less efficiency and higher fuel consumption. I called Subaru tech support about my concern and was told that everything was working within proper parameters . My dealership organization also includes Subaru franchises, and when I asked several Subaru techs the same questions I received the same answers. Sorry, but I don’t think your 30k maintenance has any bearing on your higher consumption figure. I would put more credence in weather related. If there were a fault occurring, your “check engine malfunction indicator” light should be activated. Pray for warmer weather and summer grade fuel.

“Also they replaced my entire transmission the first time I brought it in following this maintenance when I complained about fuel mileage.”

I am VERY skeptical about them replacing your “entire transmission” as a result of a complaint about a drop in gas mileage. Please get out your invoice from that visit, and post exactly what is printed on it, so that we can read it.