95 Legacy 5 speed, bad fuel economy. Suggestions?

[nicholi2789]

Alright. So a few months ago I bought a 95 Legacy 5 speed, AWD.sedan. It had 255,000 miles on it but the price was right (700$), and had a clean title so I bought it. It has a few mnor problems, like leaking a tiny amount of power steering fluid onto the exhaust so it smokes a tiny bit. and some minor engine oil leaks. But it starts every time, all the electrical stuff works (lights, windows, etc,). I've been driving it non-stop for over two months now and it has been a champ. I absolutely love it. It also had nice new Toyo tires on it and the suspension seems to be good. One thing I have noticed lately though is I'm not getting as good of fuel economy as I would expect. It costs me about 50$ to fill up ( I live in Oregon), and I usually get right at 15 gallons. I know it has a 15.5 gallon tank. by the end of that tank I'm usually at about 300-315 miles on it, which comes out to right at 20-21 mpg. I do a mixture of highway and town driving, leaning more in the town driving majority. I drive 7 miles to work and and 7 miles back every day, with about another 6-7 miles of in town driving on top of that. But I also do a lot of in town driving in between and on my days off. I'm not sure what it would get if I was driving highway miles all day every day. Presumably a lot better. In the car's defense, for the first month I had it I kinda hossed on it a little bit. Nothing outragous, just driving like a boy racer and shifting at about 4000 RPMs. I hadn't owned a stick shift car in about 5 years so I was pumped. Lol. Now I drive very sedately, shifting at about 3000 and not romping on it.

Now I have already taken care of the obvious things that would help with bad fuel economy. I've changed the air and fuel filter and running a bottle of Lucas injector cleaner through every tank, I've changed the oil, changed the transmission fluid, changed the knock sensor (because I had a code pop up), PCV valve, I even run 40 P.S.I. in my tires hoping the higher pressure will help a little. No such luck. One thing though, since the car has so many miles I've been running Castrol high mileage 10W/40. Even though it calls for 5w/30 or 10w/30. I figured with as many miles it has it's not gonna hurt. But I was thinking maybe the heavier oil could decrease efficiency and therefore fuel economy...? 

 

Now you guys tell me, is this about what I should expect or should I be getting better? I figured because it was AWD it would get a little worse fuel economy, but not this bad. The people I bought it from said it got 28 MPG but I just can't see that unless they were driving exclusively highway miles. I did find this here: http://www.fueleconomy.gov/feg/bymodel/1995_Subaru_Legacy.shtml and it says for my model about 19 mpg in town. Which is about what I'm getting if not a little less.

Any suggestions on what I could do to improve it? 

I look forward to your expert opinions. 

Thanks

Edited June 22, 2014 by nicholi2789

[coxy]

Do you know the Injectors are flowing at the factory spec, I just posted another reply where somebody has issues with running poorly after replacing injectors and suggested maybe the aftermarket injectors have too high a flow rating compared to stock.

 

Factory ECU will open the injectors a set time period based on look up tables for load revs and throttle position as well as Air Temp and Water Temp these settings are fixed and related to Injectors that flow a specified ammount of fuel per Milisecond, If however they have been replaced by aftermarket ones that flow more fuel per Milisecond than factory ones it will run rich and use more fuel.

 

that could be a place to start looking, a quick search should find somebody local who can flow test your Injectors to make sure they are flowing correctly and more importantly to factory specifications.

[nicholi2789]

Do you know the Injectors are flowing at the factory spec, I just posted another reply where somebody has issues with running poorly after replacing injectors and suggested maybe the aftermarket injectors have too high a flow rating compared to stock.

 

Factory ECU will open the injectors a set time period based on look up tables for load revs and throttle position as well as Air Temp and Water Temp these settings are fixed and related to Injectors that flow a specified ammount of fuel per Milisecond, If however they have been replaced by aftermarket ones that flow more fuel per Milisecond than factory ones it will run rich and use more fuel.

 

that could be a place to start looking, a quick search should find somebody local who can flow test your Injectors to make sure they are flowing correctly and more importantly to factory specifications.

Thanks good suggestion. I had honestly thought about the injectors, like maybe they were bad or something. But the car runs amazing. Once it warms up it idles right at 750 rpms and doesn't jump at all. It never dies and always starts first try. It is also so quiet you can barely hear it. It has power too, if I put my foot in it, it gets up and goes no problem. I have no history of its maintenance though. The kids I bought it from only had it for four months and knew nothing about it. Obviously whoever owned it originally took good care of it, judging by the clean interior, nice Toyo tires, brakes, suspension, and clean title.

I thought about maybe getting it compression tested too or buying tester. Maybe I'll just have them compression tested and injectors.

Edited June 22, 2014 by nicholi2789

[heartless]

checking fuel injector flow certainly cant hurt, but in all honesty, 20-21 for mostly city driving is about right according to the EPA fuel economy estimates for this car

 

http://www.fueleconomy.gov/feg/noframes/12124.shtml

[Scooner]

You might also want to try cleaning the idle air control valve, you said it idles great and runs great but it couldn't hurt to clean it if it has that many miles. I swapped in a 2.2 into my Loyale and it's gas mileage was pretty poor so i kind of dumbly took mine off and disassembled the entire thing and cleaned it. After putting it back on, it behaves like an entirely different car. When i say dumbly took it apart i mean there is a very simple way to clean it with it still on the manifold ha. There is a write up somewhere on here about it. That might help.

[Fairtax4me]

Very rare for injectors to go bad in these. You would have noticable power problems if the injectors were bad or clogged.

How old are the spark plugs?

How old is the Front O2 sensor? Front O2 sensor will read lean, causing the ECU to compensate by adding more fuel.

Get an OBD2 scanner that can read live data, or get a Bluetooth OBD2 adapter and compatible app for your smart phone. High fuel trims will tell if the ECU is adding fuel.

 

I get about 24-25 city mpg from my 96. A bit lower if the AC is running. 27-28 on the highway with the lift kit and 4.11 final drive.

 

You should be able to do 30 highway if you keep the rpms under 3,000.

[1 Lucky Texan]

if you could get freezefram data to see the fuel trims, that might help you decide if there's still some problem to track down or not.

 

I assume the tire size is the the same as listed on the door card?

 

A bottle of Techron 'could' help restore the injectors spray PATTERN. But i wouldn't use any fuel additive in each tank.

 

make certain the plugs are proper for the car and all the grounds are good. NGK is best for plugs and plug wires.

 

Maker sure you use the OEM type thermostat and that someone hasn't pulled yours out of the car.

 

Make sure you aren't dragging any brakes. make sure the wheel alignment is OK. those could be small 'parasitic' losses to mileage.

 

BUT, I think you are close to the best the car can do given your usage. The short trips means a higher total proportion of engine time is run when 'cold' and that means injector pulses are in 'choke' mode.

Edited June 22, 2014 by 1 Lucky Texan

[legacy603]

20/21 isnt bad I wish I got that in my 97 I'm getting right around 18 mpg with a wide open intake and exhaust and I punched it out 20 over I would say your right on the money for mpg

[nicholi2789]

if you could get freezefram data to see the fuel trims, that might help you decide if there's still some problem to track down or not.

 

I assume the tire size is the the same as listed on the door card?

 

A bottle of Techron 'could' help restore the injectors spray PATTERN. But i wouldn't use any fuel additive in each tank.

 

make certain the plugs are proper for the car and all the grounds are good. NGK is best for plugs and plug wires.

 

Maker sure you use the OEM type thermostat and that someone hasn't pulled yours out of the car.

 

Make sure you aren't dragging any brakes. make sure the wheel alignment is OK. those could be small 'parasitic' losses to mileage.

 

BUT, I think you are close to the best the car can do given your usage. The short trips means a higher total proportion of engine time is run when 'cold' and that means injector pulses are in 'choke' mode.

Thanks. I just replaced the spark plugs with just Autolite copper cores (that's what the book called for) a few weeks ago, no noticeable improvement in power, idle, or mileage. I also replaced the wires with the Napa brand lifetime warranty ones. I had heard that some subys had problems with NON-NGK wires but I haven't had a problem. I've also been thinking about getting a Bluetooth OBD 2 scanner anyways. Maybe I should start monitoring data. So you recommend using Chevron w/techron fuel? Really makes a difference? Wait, I've been fueling up at chevron

anyways. And yes it has stock tire size.

[1 Lucky Texan]

you can buy Techron otc at parts stores as well as Walmart, maybe target, etc. Just use it once as instructed.

 

 

I use it maybe every year or 2 before an oil change. Some years I use SeaFoam instead. I think they have an edge on some of the other additives but, i have no experience with Lucas. Certainly though, don't use it in every tankful. (is that what you said?) that money is better spent on good gas plus, over use might throw the A:F ratio off, dilute your oil or stress the cat conv.

 

Don't over-inflate your tires too much, You lose material in the center and therefore are not really 'saving' money overall. Plus, it can be dangerous. 2-3 pounds over is OK, maybe add 1 or 2 to that if fully loaded-out.

 

Any weight you can remove from the car will help and don't drive with the crossbars on the roof.

 

You said you chaged the knock sensor. Any chance you over-torqued it or the cable is stressed? Most folks wire brush the mount area, make sure the cable is positioned the same direction as the stock sensor. I THINK the torque is 17 ftlbs. (anyone?) more might crack the sensor.

 

Both of my soobs see 95% surface streets and they both average 20 mpg. My 06 WRX goes 11 mile to work, 11 miles back home, rarely any highway. Our 03 H6 sees even shorter 'grocery getter'- type trips with rare highway use. It gets 20-21 mpg. It never got better than 26mpg on a road trip/vacation. AND, they both run Premium.

Edited June 22, 2014 by 1 Lucky Texan

[idosubaru]

I would igonre it until you get a nice 200 or 300 mile trip - that would be far more accurate in determining anything relevant.

 

That's about right for in town driving.   particularly if you're in the mountains, heavy on the gas, always running late...lots of variables.

And it's summer blend gas now right?  And you're probably running gas with ethanol?

 

Brakes - dragging brakes are common due to old dirty/corroded slide pins. 

1. Clean the slides well, make sure all pins slide smoothly and are well greased.

2. Clean or replace the metal pad clips if they're twisted, rusty, gunked up.  they hang the pad and keep it from easily pushing off the rotor when you left off the gas.

 

Leaky injectors

 

Lazy front O2 sensor (rear can not affect mileage)

 

Air filter, PCV valve

[nicholi2789]

you can buy Techron otc at parts stores as well as Walmart, maybe target, etc. Just use it once as instructed.

 

 

I use it maybe every year or 2 before an oil change. Some years I use SeaFoam instead. I think they have an edge on some of the other additives but, i have no experience with Lucas. Certainly though, don't use it in every tankful. (is that what you said?) that money is better spent on good gas plus, over use might throw the A:F ratio off, dilute your oil or stress the cat conv.

 

Don't over-inflate your tires too much, You lose material in the center and therefore are not really 'saving' money overall. Plus, it can be dangerous. 2-3 pounds over is OK, maybe add 1 or 2 to that if fully loaded-out.

 

Any weight you can remove from the car will help and don't drive with the crossbars on the roof.

 

You said you chaged the knock sensor. Any chance you over-torqued it or the cable is stressed? Most folks wire brush the mount area, make sure the cable is positioned the same direction as the stock sensor. I THINK the torque is 17 ftlbs. (anyone?) more might crack the sensor.

 

Both of my soobs see 95% surface streets and they both average 20 mpg. My 06 WRX goes 11 mile to work, 11 miles back home, rarely any highway. Our 03 H6 sees even shorter 'grocery getter'- type trips with rare highway use. It gets 20-21 mpg. It never got better than 26mpg on a road trip/vacation. AND, they both run Premium.

 

No I didn't mean every tank full. Just the last time I filled up. I run ONLY non-ethanol premium. Ethanol gas is nasty stuff. I have no idea what was run in it the other 250,000 miles though. And no, when I replaced the knock I made sure it went in the exact same way as the old one and torqued it to spec which was 16 ft/lbs. I've always had really good experiences with Lucas additives. They are really popular here.  

[86BRATMAN]

You're actually hurting things running higher octane than required, not to mention wasting money on premium. I run my 97 5mt L on 87 non-ethanol exclusively. I average 27-28 in town and 31-32 highway.

[nicholi2789]

You're actually hurting things running higher octane than required, not to mention wasting money on premium. I run my 97 5mt L on 87 non-ethanol exclusively. I average 27-28 in town and 31-32 highway.

Yeah well, Premium is the only non-ethanol gas I can get in my town. I don't know if they even make regular non-ethanol gas but I haven't seen it. All I know is all my other cars ran terribly on ethanol gas and my chainsaws can't use it at all, unless I want unreliable saws. 

[1 Lucky Texan]

You may be wasting money running the premium, but I don't see how it could be harmful.

 

I certainly am no ethanol promoter, but I doubt your car would be harmed by using the regular with 10% or w;ever ethanol.

[86BRATMAN]

I've had vehicles that have ran worse with premium than regular, but if premium is all you can get without ethanol I'll support that decision.

[turboguzzi]

checking over a long trip/full tank of highway will give you a much better idea if you have bad mpg. city driving can have so many variables. if you get 26-27 highway then you dont have much to worry about.