Mpg

[lingling1337]

I replaced a gummed up pcv valve and picked up 3 mpg. Awesome.

[JJr]

Just returned for a 1600 mile highway only trip 70-72 cruise crontrol, boost only for passing, 26.7 mpg, I normally get 15-17 in town with many hills in my commute.

[mkee87]

I get about 42mpg. I am however talking about myself. I walk about 42 miles to every gallon of beer I drink

[rob-2]

Just returned for a 1600 mile highway only trip 70-72 cruise crontrol, boost only for passing, 26.7 mpg, I normally get 15-17 in town with many hills in my commute.

 

Must have been flat. I went from 4500 feet to 7300 feet, down to sea level, and then back in 440 miles and got all of 21 mpg

[JJr]

Must have been flat. I went from 4500 feet to 7300 feet, down to sea level, and then back in 440 miles and got all of 21 mpg

 

Reno to Gilbert AZ, some hills after Hoover Dam and parts of AZ. Normally get about 25 mpg Reno to Bay Area and back.

[rob-2]

Reno to Gilbert AZ, some hills after Hoover Dam and parts of AZ. Normally get about 25 mpg Reno to Bay Area and back.

 

Maybe it's speed or tranny difference?

[dbrunone]

Geez 18mpg is normal for you guys? I can't remember the last time I saw lower than 22, and I'll get up to 28 on the highway in the summer. Usually get 26-27 on heavy-traffic highways to and from work

[Max Capacity]

Filled the wagon Friday on the way home, it sat all weekend while we took the Spec B to VT. Drove the wagon to work today, with about 35 miles on the tank, the dash is reading 28.2mpg. I was doing 65-68mph on the drive in.

 

The Spec had some mixed miles and sitting in traffic for a bridge closure yesterday, made a U turn in the grass and headed back north to take the backroads like everybody else, (lost over a 1/2hour there) it read 25.3 when I filled after 320+ miles.

[covertrussian]

My city MPG is around 17 now that it's warm + summer gas. That's actual, gauge MPG is always optimistic at 18-19.

 

Highway was around 27 actual, now with more tuning got almost 30 actual. Funny thing gauge read 27.4 when I got 29.60 actual.

[ripstik]

Funny thing gauge read 27.4 when I got 29.60 actual.

 

huh? interesting high at low MPG and Low at high MPG I wonder why.... wait was this after the tune? did it do the same for city mileage also after the tune?

[covertrussian]

huh? interesting high at low MPG and Low at high MPG I wonder why.... wait was this after the tune? did it do the same for city mileage also after the tune?

 

The gauge is simply inaccurate, it's only good for a baseline and should never be trusted as 100% correct. Even when my car was bone stock I've had the gauge be 15% off.

 

On average, the gauge is 7% off city (too optimistic), and -7% off highway (too depressing ).

 

It's not something you would see unless you constantly record this data. I note down city miles vs highway miles, ambient temperatures, tire offset (speedo innacuracy), AC usage, drive style and locations. I also use the same gas station and pump if at all possible for all of my cars.

 

End result is, I can see trends in gas mileage compared to external conditions or mods. This is how I knew when my local gas stations switched to winter gas. MPG on my FXT instantly dropped to 16 from 18 in November and back up to 18 in March

[rob-2]

The gauge is simply inaccurate, it's only good for a baseline and should never be trusted as 100% correct. Even when my car was bone stock I've had the gauge be 15% off.

 

On average, the gauge is 7% off city (too optimistic), and -7% off highway (too depressing ).

 

It's not something you would see unless you constantly record this data. I note down city miles vs highway miles, ambient temperatures, tire offset (speedo innacuracy), AC usage, drive style and locations. I also use the same gas station and pump if at all possible for all of my cars.

 

End result is, I can see trends in gas mileage compared to external conditions or mods. This is how I knew when my local gas stations switched to winter gas. MPG on my FXT instantly dropped to 16 from 18 in November and back up to 18 in March

 

I'm somewhat impressed by your data collection and then want to know how you have the time for this?

[nouse4aname]

The average shown on my trip meter is virtually identical to what I get calculating by hand and logging to fuelly. My commute must just be a perfect blend of driving environments to even out heh.

[covertrussian]

I'm somewhat impressed by your data collection and then want to know how you have the time for this?

 

Every time I fuel up I just write the tripo miles, total miles, and gauge MPG on the receipt and then input it into a spreadsheet (along with what I remember the driving conditions where for that week). Takes 10 minutes tops, so it's not bad really. It takes me much longer to take pictures, resize, upload and write posts in my build thread

[rob-2]

Every time I fuel up I just write the tripo miles, total miles, and gauge MPG on the receipt and then input it into a spreadsheet (along with what I remember the driving conditions where for that week). Takes 10 minutes tops, so it's not bad really. It takes me much longer to take pictures, resize, upload and write posts in my build thread

 

The raw data interests me. The collection doesn't change my driving habits or improve my MPG.

 

What's been the upside to collecting?

[covertrussian]

The raw data interests me. The collection doesn't change my driving habits or improve my MPG.

 

What's been the upside to collecting?

 

It's especially important when you are tuning, since running a little too much timing could lower your gas mileage. It's also important to gather raw data, and frequently, to see if a mod improved or decreased gas mileage.

 

Like when I did the Invidia up pipe I had to get a new O2 sensor and did a front wheel bearing all withing a couple weeks range without doing highway tests in between. Then when I actually got around to going I noticed my gas mileage dropped by 3mpg, At that point I just didn't know what to point my fingers to, this is why I've been trying to keep variables down since then.

 

I've only had the car since November, thus my data set is still fairly small, but this car renewed my interest in driving thus I've been driving a lot more. I have 50 fillups on the legacy, I've owned a Forester XT for over a year and it's still only at 36 fillups...

[rob-2]

Oh I'd just data log for that, not record MPG

[covertrussian]

Oh I'd just data log for that, not record MPG

 

Data log only goes so far, even the estimated fuel economy gauge in romraider wont be accurate (As accurate as stock gauge, but less useful because your only looking at calculated MPG from when you plugged your laptop in).

 

I've looked at logs for years and never could really see MPG improvements. Only time I would really get real feedback is at the pump. This was especially the case with one of my Nissans, I turbocharged the stock motor (9.5:1 compression), installed a better flowing intake manifold, side gapped plugs, and was trying to run stock amount of timing in cruising areas on it (36* or so). My MPG would be at 31-32 at best, I tried increasing timing in steps from 36* to 42* and MPG continued to just stay the same or actually drop.

 

Then I started thinking differently (you will always hear people say more timing = more gas mileage), well I realized that with a new intake manifold (stock from another motor) and turbo, the motor was much more efficient then it was bone stock. When you hit your efficiency peak, extra timing actually creates resistance for the pistons. At that point I started reducing my timing, I got it down to 24* cruising and my MPG jumped to 36-38mpg.

 

I'm not saying this will work on a Subaru though, EJ heads are not efficient, plus inefficient headers (that we all love though), plus tiny turbos. I'm slowly trying to work around these issues and documenting it for others to see.

 

Point of it being, looking at logs could get me only so far, sure you can try to guess it based on vacuum gauge, TPS, injector pulsewidth, etc. But that all is a lot harder to make sense of then simply doing one change, driving 120 miles, fueling up and getting the actual numbers

[chisav]

After I was retuned my mpg meter says around 22-24 depending on how much highway/city.

[lucasguarien]

MPG gauge, its just a lie for me..., i just use it as a parameter to know if what i'm doing its good for my "econo-driving".. haha.

[rob-2]

How accurate does it really need to be guys? I mean honestly if doesn't swing 50%, nor 25%, it's only every been off by about 1mpg for me, and maybe part of that is to blame for where the fuel cuts out.

[covertrussian]

How accurate does it really need to be guys? I mean honestly if doesn't swing 50%, nor 25%, it's only every been off by about 1mpg for me, and maybe part of that is to blame for where the fuel cuts out.

 

10-15% can be anywhere from 1mpg to 3mpg depending on how good your mpg is. The more your getting the more per percent you loose.

 

Let me get you some raw data to understand why it's important to have accurate data to tuning, in this case I am tuning AVCS tables.

 

Tune - Gauge MPG - Actual MPG

AVCS 0 - 25.8 - 24.65

AVCS 10 - 27.0 - 25.88

AVCS 15 - 27.4 - 29.60

AVCS 30 - 25.2 - 23.17

 

As you can see the gauge can go from being optimistic to not so much, just too inconsistent to really on.

 

But it MPG gauges do have their place, they force people to be more throttle conservative because they see their MPG dropping in real time.

[rob-2]

10-15% can be anywhere from 1mpg to 3mpg depending on how good your mpg is. The more your getting the more per percent you loose.

 

Let me get you some raw data to understand why it's important to have accurate data to tuning, in this case I am tuning AVCS tables.

 

Tune - Gauge MPG - Actual MPG

AVCS 0 - 25.8 - 24.65

AVCS 10 - 27.0 - 25.88

AVCS 15 - 27.4 - 29.60

AVCS 30 - 25.2 - 23.17

 

As you can see the gauge can go from being optimistic to not so much, just too inconsistent to really on.

 

But it MPG gauges do have their place, they force people to be more throttle conservative because they see their MPG dropping in real time.

 

The argument is flawed because the nozzles aren't accurate enough. As in they don't all stop at the same level every time.

 

At best we are getting approximately the right gas, and our mileage is within 3% of fact.

[K2e2vin]

Earlier today, temp around 69F and driving about 60mph on the highway, I was getting 33-37mpg(gauge) on flat ground! Still had my snow tires on too along with mud-flaps.

 

Boost/vacuum gauge helps a lot and as far as influencing driving techniques, IMO it works a little better than using the MPG gauge. Though, what I've noticed the most is I get crappy MPG with "abrupt" changes in throttle; I'm assuming tip-in is pretty rich.

[rob-2]

Earlier today, temp around 69F and driving about 60mph on the highway, I was getting 33-37mpg(gauge) on flat ground! Still had my snow tires on too along with mud-flaps.

 

Boost/vacuum gauge helps a lot and as far as influencing driving techniques, IMO it works a little better than using the MPG gauge. Though, what I've noticed the most is I get crappy MPG with "abrupt" changes in throttle; I'm assuming tip-in is pretty rich.

 

Boost.