Gas milage

I assume you've taken into account things like weather conditions, possibly low tire pressure or slightly different tire size and logged the difference over more than one tankful.

One possibilty is the engine temp sensor (not temp gauge sender) The ETS can fail in such a way that it prevents the ECU from leaning the mixture out. It basically thinks the engine is cold and the 'choke' should be set all the time. It can fail and NOT set a check engine light I think.

Carl

You don't say over what sort of mileage the change has occured. Everything in previous responses sounds good. IME gradual deterioration is more likely caused by a consumable item needing changing, sudden deterioration by a component failure or loss of adjustment. Cheers

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mmm, thermostat?

Uncle Ben wrote:

I have my vote for all of the above---

Thermostat, air filter, tire inflation/condition.... any chances you're running the car longer to warm up in the mornings? also take into consideration changes in local fuel supply... my 98 hates ethanol and runs poorly on it to prove it.

lastly...any check engine light/codes pulled? Even intermittent (and self clearing) could indicate a problem to be checked more closely.

It never hurts to install a fresh air filter, but in my experience it's not going to make much difference unless the one currently installed is really dirty. I'd try the plug wires first, and get a good set that fits well, particularly the cap at the coil end. This is a common issue on the 2.2l motors, especially as they get older. You will be amazed at how much better your car will run if you replace plug wires that _are_ starting to go out . . .

Beyond that, check the engine coolant temperature sender as someone has already suggested (check by replacing it; only about a $10 part IIRC). There may be two temperature sensors on your car (the second one works the instrument panel gauge), if so, be sure to replace the right one. Also run an OBD II diagnostic and engine compression test.

FWIW, oxygenated fuels can (will) cause mileage to drop as well; usually around 10%. I'll assume you have already taken this into account.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

This is just to acknowledge the 6 generous people who are trying to help me regain the good milage I used to get in my 1999 Leg. OB. At last I am getting around to trying out their suggestions.

1. I don't know whether the problem arrived suddenly or over a period of time, since I don't check milage often enough.

1. I have now replaced the air filter and will find out soon what effect that change causes. I have a regular appointment on Wednesday evenings that takes me 240 miles. (The old one looks pretty black to my untutored eye.)

2. I have new plugs and have ordered new ignition wires, The plugs are so deep into the engine compartment that I will get my mechanic to make the replacement.

1. The other suggestions will also require the mechanic's help, so I'll report later if any temperature sensor replacement has any effect. I doubt it because a too-rich mixture should cause some smoke out the back if it is severe.

2. Tires are new and the change in diameter is in millimeters of tread. I am looking for a 20% effect, so I doubt that one.

Thanks again to you guys.

U.B.

Air filter. --

Wow! With a new air filter, I made my Wednesday night trip of 240 miles. The gas milage increased from 24 mpg to 32 mpg. Quite a return on my $8 investment. I have learned to change the air filter every 150,000 miles whether it needs changing or not! :-)

Plugs --

I won't have a good test before next Wednesday, but I learned something interesting. For 8 years I thought I had a 2.2L engine, it turns out that I have a 2.5L engine. As such, it is recommended to use platinum plugs. Four platinum plugs run $100+ ! And the wires cost another $100.

I chose the non-platinum plugs, but I had to take the high-priced wires. Next Wednesday I will again measure the milage. But my goal of 30 mpg has already been met with just a change of air filter. It is hard to believe that the new plugs will take the mpg from 32 to 40!

I won't report again unless there is an unexpected result.

U.B.

150,000 on an air filter? A little sooner would be good too. :)

Since you're already in the market place buying things, care to make an offer on a bridge? Only joking.

The prices for plugs and wires, umm, does that include installation, or is that going to cost you extra? I don't suppose your mechanic mentioned how platinum plugs are going to raise your fuel economy so well? If it were this easy, FHI would use those plugs in all their vehicles to get around classifying some as trucks to meet mileage requirements. You might find out the brand of plugs you are being sold and post here, as some really do not work well in Subies.

Your costs sound a little padded to me.

If you are putting performance wires in instead of standard I could see $100, but you have to understand that low resistance wires tend to hit a coil harder and tend to require a coil that can recoup faster than the standard. I would figure it to be similar with a coil pack setup as your Subie would have.

For the $200 in plugs and wires you are looking to spend, you could pay for

3 or 4 standard plug/wire sets.

On the other hand, when the air filter in my brother's BMW was as black as night, he had similar problems. Course, after he tuned-up the motor the transmission went.

~Brian

The platinum plugs are recommended by Subaru for the 2.5L engine, so I'm safe there. Installation is extra, and well worth the price, because to install the plugs you have to disconnect the engine mounts and raise the engine -- or something like that. Standard labor charge is for 1.5 hrs.

No, it's not *that* hard. I did all four in about 30 minutes, and I've never done them on this car before. And I'm no mechanic, either.

-John O

Thanks, John. The mechanic I dealt with is highly touted in these parts for honesty and knowledge, but this was the first time I used him. Maybe I'm getting educated!

Replacing them does require the removal of the air filter assembly on the passenger side and the washer fluid resevoir on the driver's side. Maybe it's easier for them to mess with engine mounts instead? Either way, it's a PITA to replace the plugs, so install good ones that will last.

-John O

On Feb 15, 11:11=A0am, "John O" Replacing them does require the removal of the air filter assembly on the

John, after studying under the hood a while, I think you've got it. My mechanic has already put in the low-priced plugs. In 30,000 miles they should be ready to be replaced and I am going to try your method.

Thanks very much.

U.B.

You're welcome, but I can't take the credit...someone else here mentioned it and posted some good instrux long before me. :-) I bought a 3/8 knuckle adapter and a short extension that allows some flex, anticipating this was going to be trouble. Turns out that the plug socket and ratchet were all I needed. It was tight, but it worked. I bought the Stanley set of sockets at Walmart.

-John O