05 legacy gt gas mileage questions

So I recently just picked up a 05 legacy gt. This is my first car and really don't know much about them. But anyways the previous owner did a couple power mods to that included a catless dp and up, and a intake. The owner said he had a mild tune done to compensate for the mods that were installed. But he "didn't" remember who did it. The car drives and runs fine, but I'm just a little worried because my daily drive to school is 10 miles in the city there and back, and somehow I only average 15mpg, and that is me driving as efficiently as possible. Could the tune that the previous owner put on it be causing this? Or does 15mpg seem about normal?

15MPG if pure city, in a tuned vehicle is a little lower than I would expect, but not by much.

My DD is 32 miles one way mostly highway both my cars will get 24 mpg or better. In all my years here I’ve learned these cars don’t do well with your kind of DD.

Take it for a long drive on the highway at least 10 miles or so weekly.

I get about 18mpg mixed driving (primarily city).

I get about 18 mostly city and 24-28mpg on hwy dependent on speed.

Even with colder weather coming, there is no need to let these cars warm up in the driveway. Just start it up and drive it easy for the first few miles.

Our NA 2006 gets about 18-20 in a short trip city condition with 1-3 mile trips. The 2002 H6 gets about the same, but is also running a heavier than spec oil to quiet down noisy timing chain.

 

So, 15 is likely within reason for a tuned vehicle in super short trips. Check tire PSI, brake calipers for sticking.

My commute is about 16 miles round trip, all stop and go. I get an average of 19 MPG summer and 17 in the winter. Like Max I get 24 if all highway driving. Car is an OBXT with a 16G Td05 turbo, catless up and catted dp.

15 mpg seems pretty low to me. I average 26 mpg with about 80% highway driving and pure city I get around 20-22 mpg. Pure highway I get close to 30 mpg but it seems like my fuel economy isn't the normal haha

19 city, 24 highway for me on my DD, ('08 stage2 outback w/ VF52). Boost=crap gas mileage in our cars

If you can pull the ROM from the ECU, via a tactrix cable, then we can see if you actually have a tune or not. I would be hesitant to drive something that the previous owner didn't know the real history of. 15mpg is low if you're staying out of boost.

5eat in a lgt will see about 18mpg mix between city and highway. All city about 15mpg. All highway about 24mpg.

Sounds about right, maybe a little on the low side but depending on the mods and tune it doesn't sound crazy low. These cars don't like a lot of city driving. Especially short trips before the engine warms up they use even more gas, and idling just pisses it away. In my '05 I average about 22mpg this time of year and do roughly 75% highway miles, the rest around town. Not much actual "city" driving. On long highway trips in warmer I have gotten as good as 25mpg, but just farting around town I get much less. In cold weather in an actual "city" setting with lots of stop and go I don't get much better than yours.

Stock with Catless Up-pipe.

 

23 at best highway trips (usually carrying bike on back)

 

17/18 around town.

I actually have a very similar daily commute, start the car, drive 4-6 miles, shut it off. This is harsh on all cars, and all cars will have crappy gas mileage turbo or not.

 

Since I also have an 05 5MT my numbers will mean more then 5EAT numbers.

 

When I was stock to mild stage 2, I would get up to 18-19mpg when it's warm and down to 15-16mpg when it's freezing out.

 

Nowdays on stage 3 setup, my car is getting 20-21mpg when warm and 17-19mpg when cold. I bet I could get the same numbers on the stock turbo with my current tune.

Stock engine, no tune. 20 miles to work and I average 21.6mpg. 15mpg sounds too low.

I have owned 8 subies and 5 lgts. Along with working on thousands. 15-18mpg city is normal for a 5eat 4th gen lgt. You can get more, but you have to consciously work at it.

Stock engine, no tune. 20 miles to work and I average 21.6mpg. 15mpg sounds too low.

 

20 miles one way = 40 miles a day, that's a heck of a lot better then 10-20 miles a day that OP and are doing. Cold starts are the enemy of theses cars.

 

I have owned 8 subies and 5 lgts. Along with working on thousands. 15-18mpg city is normal for a 5eat 4th gen lgt. You can get more, but you have to consciously work at it.

 

OP's profile says he has a 5MT.

5mt can get slightly better mileage. A specb 6mt can get 30mpg freeway if driven just right.

5mt can get slightly better mileage. A specb 6mt can get 30mpg freeway if driven just right.

 

Right, I just saw you referencing 5EAT a few times, figured you missed that OP's car is a 5MT .

 

I really wanna test drive a Spec B, I've been getting 27-29mpg on my 5MT LGT since day one, thus I wonder what a Spec B would do with me driving it. I don't hypermile or do any trick driving, just set cruise to 70mph, accelerating to 75mph when passing, but I never go into boost.

 

With city MPG test I don't go into boost either, but where I live there is a bit of traffic, 0 mile above 50mph, lots of hills, and lots of cold starts, so my city MPG is always much lower then average.

Staying out of boost is a big part of it. Difficult to do on the stock tune as most 5mt are at about 3000rpm at 70mph and on boost (2psi-3psi). You are getting very good results with your 5mt.

Staying out of boost is a big part of it. Difficult to do on the stock tune as most 5mt are at about 3000rpm at 70mph and on boost (2psi-3psi). You are getting very good results with your 5mt.

 

Yeah that's what I noticed too, for a while I thought it was due to a small turbo, but it's actually because of the wastegate tables. Thus I believe zeroing out the partial throttle wastegate duty cycle table is what helped me on the stock turbo.

 

It helped to the point that getting a bigger & laggier 16G didn't help gas mileage at all.

Cant say I have seen mpg increases from a 16g. Nor an 18g. Most customers looking for turbos in that size range are what I refer to as "stop light assassins". I actually enjoy the power delivery of these turbos. It can be quite a bit of fun when top speed is not the goal.

 

 

 

In the end, the cars were never built for fuel efficiency. Even the N/As dont get great mpg (I get about 26mpg hw in my 03 Forester XS 5MT). Subaru did not start working to increase that until Toyota got involved.

Right even 2009 NA Outbacks are still pretty bad. In 2010+ the finally started doing much more respectably (even non CVT models).

 

Anyway, 15MPG is not that far from normal for these cars in 100% city driving

I keep a log. Here's what I get assuming I can post Google drive links.

 

I'd say 2-3 months ago I put on a vf39, FMIC, EBCS, ELH, 3 inch down pipe, and water methanol injection kit. I do not drive efficiently, often bringing her up well over 6000 rpm. She drinks oil like an alcoholic at an open bar.

 

According to the maths I'm getting an average of 18.2 and change mpg, which seems high. Mixed driving, but mostly city. 8 mile commute 1 way to work. Also a grocery getter. Haven't driven her much this month as I'm breaking in the STI engine.

 

https://docs.google.com/spreadsheets/d/1FKUAeArsfXYZ24tDWjtVIpiXP9YZUdSd_6jUFWO82FA/edit?usp=drivesdk