EJ25 spark plugs and fuel economy

[LegaWaga]

So lately, my fuel economy in my 2000 Legacy Wagon had dropped poorly to around 20mpg, and even less at times. This is on a highway tank too. I knew I was overdue new spark plugs, so I decided to go that route. I got the NGK iridiums so that I can have some life on these plugs. I do a lot of driving. The computer and a google search said they OEM gap is .044. Both the plugs I pulled (v-powers) and the plugs I installed were at exactly .040. I did regap the new ones to the specified .044, though I have heard some recommend against it. Either way, I have noticed a slight improvement in power, and we will see how the rest of the tank goes.

I do also have a "short ram" intake, which I am also doubting, but it has been on the car for a little bit with no huge change in power or mpg difference. I will probably be replacing it with the factory intake again soon either way.

What are your thoughts on the wrongly gapped plugs, the intake, the mpg, or anything else. I need to get more than 200 miles per tank.

also, the motor has around 115K miles.

Thanks!

[Garrison]

Short rams don't do anything besides make noise, ditch it for a CAI setup, or OEM.

[LegaWaga]

With stock exhaust, does a CAI even improve anything? Mine doesn't even really make noise. :(

[Huffer]

You probably want to do an upper engine cleaner - Subaru has a service where they clean carbon deposits from the upper intake pre-cylinder.
Check your airfilter, your PCV and the EGR system. A poorly running EGR system can result in poor MPG.

[LegaWaga]

I forgot about the egr stuff. This is the newest car I own. Lol I will probably replace the egr valve and the wires to be safe.

[unsullied_spy]

Gapping an Iridium plug is very risky, the little Iridium piece is very brittle and can easily be cracked with a gapper. If your wires haven't been replaced recently replace those, run the V-powers (to eliminate chance of a damaged plug), dump a can of Seafoam in the gas, run some upper-end cleaner through it, and with the Seafoam in the gas (or whatever injector cleaner you like, I prefer Techron but it's spendy) go hold your foot on the gas for a good 0-70 or 0-80 run and that should blow some crap through it. EGR valve could be a culprit, but very spendy. Keep it cheap and simple until you've eliminated other posibilities, IMO.

EDIT: What speed you drive on the highway also affects fuel economy a lot. My 04 will do about 33 MPG if I keep it to 55 MPH, around 31 at 65, 29-30 at 75, and drops to around 27 at 85 all at 5,000+ ft. elevation. 115k miles is kinda low for a plugged cat, but it may be worth checking that out as well. If the cat is plugged you'll have a lot more backpressure and the engine won't breathe right, losing power and fuel economy. Also, the AFR sensor may be due for replacement. They typically seem to last 100k-120k miles and can cause a loss in power as well as fuel economy. Do the '00 models still have a MAF? If so some CRC MAF cleaner is in order, that stuff works wonders on higher mileage MAF sensors.