MPG question

[Bigbusa]

My 180k mile 1996 obs 2.2L auto is getting 17.5 mpg city. It is below freezing here so that will probably lower the MPG some. Still, 17.5 mpg seems pretty low.

 

What should I check and/or replace on my engine for better MPG? It was tuned up with new wires at 160k miles. I just replaced the air filter too. Tire pressures all checked.

 

On a positive note, I can't believe how easy it was to replace the rear rotors and pads! Remove the wheels, remove a bolt on the caliper, flip it up and pull it off. Remove 2 bolts on the pad holder, slide it out, put in new pads, reinstall holder, slap on new rotor, squeeze caliper piston with a clamp, install it, adjust parking brake star wheel with my finger and slap on wheels. 15 mins tops per side.

 

Are the front brakes this easy? I'm doing them next.

[Skip]

lazy A/F ratio sensor**

 

winter fuel blend

 

CTS not up to stuff

 

brakes hanging up

 

to name a few

 

 

 

 

 

 

** sometimes called an 02 sensor.

[Bigbusa]

lazy A/F ratio sensor**

 

winter fuel blend

 

CTS not up to stuff

 

brakes hanging up

 

to name a few

 

 

 

 

 

 

** sometimes called an 02 sensor.

 

 

skip thanks for the advice. Brakes aren't hanging up. That I know.

 

O2 sensor possibly ...but I do not have a check engine light indicating a problem.

 

What is the CTS?

 

Winter fuel blend ... possibly an issue but I can't control that.

[Skip]

you're welcome Busa

 

kewl on the brakes

someone else recently posted that was his problem

just paaing it along

 

wheel bearings and alignment were also mentioned

 

 

Lazy 02 will not trigger the CEL

Since you just bought this car

I will assume you do not know

the age of the 02 sensor.

 

Might be a good starting point?

 

CTS - Fuel Injection Coolant Thermo Sensor

also if just not quite up to stuff will not

throw a CEL.

You could pull a spark plug and look for a rich mixture.

 

All my Subarus (too many to say) all loose 2 or 3

MPG in the winter.

[screwbaru2]

old pcv will bog an engine also the pcv hose sometime gets clogged.

[idosubaru]

you mentioned ignition wires, the plugs should be replaced too...were they already replaced, is that why you didn't?

 

fuel filter, air filter are good ideas too.

any check engine lights recently?

have the valves ever been adjusted - they are recommended at 100,000.

at least the 97's have adjusted valves...not sure if the 96's have HLA's, if so they may not need adjusted.

 

brakes hanging up.

an important thing to remember about skip's suggestion is that you may not notice anything abnormal with the brakes. you want to make sure you regrease the caliper slides with BRAKE SPECIFIC caliper grease, not ordinary grease. they sell it at the stores, often little packs at the counter for a brake job. the slides loose grease over time and the brakes will drag...not enough to cause any issues, but enough to reduce gas mileage. i've seen mileage go up 2-3 mpg on a perfectly running vehicle after a brake job.

 

yes the fronts are basically just as easy. you should remove the brake fluid reservoir cap to make sure the pushed fluid has a place to go and doesn't blow the seals in your master cylinder. the fronts are just a bit bigger, but easy.

[zrbrat]

Maybe the tire pressure is lower because of the colder temps? Might be a combination of different things also.

[Subarupusher]

My 100K 1996 Impreza Outback 2.2 Auto gets 22-24 with the winter blends.

 

Definitely something holding yours back. I think my bearings need servicing soon so maybe that is a possiblity for you if they have never been looked at.

[ericem]

old pcv will bog an engine also the pcv hose sometime gets clogged.

 

Definitely agree with that mine was really clogged up when I replaced most of the PCV system.

[Bigbusa]

ill check that today. thanks

[Bigbusa]

lazy A/F ratio sensor**

 

 

 

 

 

** sometimes called an 02 sensor.

 

I bet youre right! My check engine light just came on tonight.

 

Earlier today I made an appointment for a state inspection sticker ...tomorrow. If I unhook the battery, hook it back up and start the car, will the check engine code go off... at least temporarily?

[zstalker]

lazy A/F ratio sensor**

 

** sometimes called an 02 sensor.

 

A/F sensor =/= O2 sensor

 

O2 sensors and Air/Fuel sensors use a different type of sensor in the exhaust stream, and produce a different type of voltage output.

http://www.aa1car.com/library/wraf.htm

this sin't to say that it may be getting old (if your car even uses an A/F sensor), but just to clarify

[uniberp]

A/F sensor =/= O2 sensor

 

O2 sensors and Air/Fuel sensors use a different type of sensor in the exhaust stream, and produce a different type of voltage output.

http://www.aa1car.com/library/wraf.htm

this sin't to say that it may be getting old (if your car even uses an A/F sensor), but just to clarify

 

Also, engines are noisier when very cold, and I think the knock sensor picks up more rattle and retards the ignition more in winter. I firedu up the very cold Legato and took off quickly in a hurry a couple weeks ago and it still hasn't reset to normal, feel like. It hasn't forgiven me yet. And gas mileage is down to around 22.

[Skip]

agreed Z -> semantics

 

why I said "sometimes"

 

It is common vernacular to call them

"Wide Band 02 sensors"

 

from your link

Wide Range Air Fuel (WRAF) sensors, also called Wide Ratio Air/Fuel sensors,

Wide Band Oxygen Sensors or Air/Fuel (A/F) Ratio Sensors,

are replacing conventional oxygen sensors in many late model vehicles

 

 

Both types monitor the 02 content

and the ECU uses this to calculate

the approx A/F ratio.

 

The Wide Band is a variable output

(think volume control) where as

the Narrow band is almost like an on/off switch.

 

Good link by the way.

[rick_hake]

Tests have shown a mileage increase of 2 to 3 mpg with the use of Synthetic Oil. It seems pretty expensive, but the extended drain intervals make it work out to an advantage in price over petroleum based oils.

Because of the expensive nature of the Synthetics you wouldn't want to use them if you have an oil leak. The stuff is super slippery so if you have a very small leak you could end up haveing a big leak.

As in petroleum based oils some are better than others so if you decide to go this route be sure to compare the test data available to get the most bang for your buck unless you just don't care, but if you want the best mileage you want the best synthetic.

Rick

[subaruloverbrad]

I just made an trip from bristol VA to the southern edge of PA in my auto full-time 4wd 1991 Legacy and got an average of 31.6 mpg with body damage 234K miles and a i belive slighty out of alignment frontend (pulls to the right) Something must def be wrong.

[OB99W]

I just made an trip from bristol VA to the southern edge of PA in my auto full-time 4wd 1991 Legacy and got an average of 31.6 mpg with body damage 234K miles and a i belive slighty out of alignment frontend (pulls to the right) Something must def be wrong.

Yes, but Bigbusa was talking about New York City (stop-and-go) mileage. While 17.5 mpg could probably be improved on a bit, that's "Big Apple" mileage versus your highway "orange" 31.5 mpg.

[subaruloverbrad]

oh ok here in bristol its not so stop and go. i hate ny traffic.

[idosubaru]

31.6 in an AWD automatic...WOW.

 

i'm not entirely surprised since an XT6 can get 28 mpg with 6 cylinders and 145hp in the same combo - AWD automatic. but i haven't heard many people quote those kinds of numbers for AWD EA stuff. but of course....not many people drive entirely highway miles either.

[Reveeen]

31.6 in an AWD automatic...WOW.

 

i'm not entirely surprised since an XT6 can get 28 mpg with 6 cylinders and 145hp in the same combo - AWD automatic. but i haven't heard many people quote those kinds of numbers for AWD EA stuff. but of course....not many people drive entirely highway miles either.

 

I get 36-38 here (careful highway) '91 2.2T AWD auto, I would consider myself LUCKY to see 18 in the city, in winter.