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WRX Quest for MPG

I use my 2008 WRX for onsite tech calls, with which I rack up 40k-50k miles a year.

This means a minimum annual fuel cost of $4709, at current cheap gas prices.

I had been getting 21-23 hyw. The dealer and Subaru basically told me that was expected and to suck it up.

Monday I reset the ECU and installed K&N Air Filter and have averaged 27mpg.

Still I remember last years gas prices and have been looking for a good E85 mod and or any other Tuning that could be done for better MPG.

Tuning is not my area of knowledge and ever web searches have been near fruitless.

I only found one place in AZ (I’m in MN) that looked interesting.

AZ Eco-Tune (

Cost for modification $2999

Dyno-Comp (Stage-2E): Performance Package:

Kit Includes:

?Magnaflow Full Exhaust System $699

?COBB Down Pipe (With High Flow Cat) $595

?1000cc injectors (for E85) $595

?Drop In High Flow Air filter Element $54.95

?Cobb Access Port $695

?(*Includes: E85, Ethanol, “Dyno-Comp” Pro-Tuned map), Claimed +2 to +6 MPG, just from ECU mod, not others.

Eco-Tune, 25-28MPG over all using E85 @ $1.99gal

Est. Fuel Cost = $3184 @ 25mpg (savings $1525)

$2842 @ 28mpg (savings $1867)

Pay Off 2 years of less.

I mean to ask that company what they think they could do for E85 + EcoTune, with out worries of increasing HP could do.

However, as I said, I am lost in this matter and would like something closer or other suggestions. I really would like E85, for the subsidized price if nothing else.

Yes, the car runs decently right now stock on E85, but the damn engine light comes on dissabling cruise and traction control.

I was not aware that the WRX was a flex fuel vehicle designed to use E85. In fact, checking the list at, there is no mention of Subaru as a builder of flex fuel vehicles.

I suppose that’s why the check engine light comes on. You’re damaging your car by burning E85. I suggest you consider another vehicle if you insist on burning this stuff. Your WRX is designed to burn premium gasoline, not e85.

The WRX is not meant to be a mileage champ. It’s a performance car. You can spend all the money you want trying to change it, but it’s still a performance car and will never get great gas mileage.

If you can get 27 on the highway with a WRX, you’re doing pretty well. My Legacy doesn’t get much better than that.

I concur with everything that mcparadise stated.

In addition to the damage that you are doing right now from the use of E85, that K & N air filter is the potential source of additional problems.

There are many reports of damage to the Mass Air Flow sensor (MAF) on cars using K & N filters. Unless oil is applied very carefully and very sparingly to those filters, the oil has a tendency to foul the MAF. If and when that happens, you will wind up with driveability problems plus repairs that are not covered by warranty.

If you want to use E85, you are driving the wrong vehicle.
If you are looking for a gas mileage champ, you are driving the wrong vehicle.

It looks like you’re rationalizing giving “AZ Eco-Tune” $2999.00 for their work because it will pay for itself with improved gas mileage. I don’t think you’ll even come close.

In fact, if you rely on your car for 40K-50K/year for work, you can expect the Eco-Tune changes to likely cause you additional “tinkering” downtime, and additional out-of-pocket costs.

You are trying to remake the car. The WRX is a “performance car”, it was designed and factory tuned to deliver fast acceleration and power. That is what you signed on for.

Now you are going to spend more money in your quest. You will not get back any of your money on mods if you decide eventually to sell the car. Adding gismo’s and gadgets to improve mpg is a gamble. The claims often don’t match the real results. You are going to spend some significant money on the hope of improvement. If the greater mpg isn’t achieved and you sell the car for a higher model mpg vehicle all your mods will get you is zippo. All this does not make economic sense to me. Speed, power, and strong acceleration all take fuel. The WRX is basically a small economy car (Impreza) hopped up into a performance car.

I’d suggest you sell the WRX privately to get the most $$$ out of it you can. Then you can buy a Civic, or perhaps a VW Desiel if you want to max out your mpg. If your priority is mpg buy a car made to maximize mpg. You will lose less money switching cars than all the time, effort, and money it will take to make the WRX into a higher mpg car.

Back in 2003 my son was considering 2 cars, a WRX amd Honda Civic. The WRX was fast and cool. Definately a nice car. I told him to check his insurance rates for the 2 cars. I also stated my preference for the Civic based on reliability, no turbo, and much better mpg. He got the Civic EX with 5 speed stick. Still has it and loves it. He is a regional mgr and puts on tons of mileage. The others at his level drive BMW’s on lease and he just banks the money and keeps enjoying the benefits of his Civic. He just bought a house. A few times early on he said he’d wish he had the WRX, but haven’t heard that in over 5 years.

I would not try to convert to E85, for all the reasons listed above. I also doubt the mpg claims made for this set of mods, most are performance, not mileage, related. This is a high output turbo motor, messing with it has the potential to create a very expensive doorstop. Yours is a situation that begs for a high-mpg highway car. A Jetta TDI, with the appropriate suspension/wheel/tire mods, would be a very fun car delivering 40+mpg.

How fast are you going on highway? Keep it at 55MPH and your MPG will average around 25 using premium.

In your case if you like Subaru, seriously consider trading to a 2010 Legacy with the CVT transmission. It gets 32MPG highway with similar room as Honda Accord.

I should really know by know that forums in general will always go off track, topic, or focus on all the wrong details. Let me try and get us back on the same page. :slight_smile:

I never said the vechical was E85 currently. I Said that it runs fine on E85 in the one tank of gas I tried.

I drive a WRX as a cummuter car for a very specific reason. It is the best MPG car available that meets the criteria of AWD. I do not live in California. Repeat. I do not live in California. I know that sounds like an odd thing to say, but internet people seem to think driving conditions in CA are what they are everywhere. My job requires that I go out to some farm house in a blizzard I’ve never been to before on poor, unplowed rural roads. I spent alot of time researching a vehical. The WRX simply had the best highway MPG of any AWD that I could find. I was also the ONLY AWD + manual vehical under $40k.

I admit I am very dissapointed with the MPG. All my other vehicals I have gotten well over the Sticker MPG and even previous Impreza’s averaged 30MPG. I was mistaken that a turbo would not effect HYW MPG. I was thinking that was the whole point of a turbo would be that it allowed higher output when wanted of a smaller engine (2.5L), and when cruising would be using the same HP to cruise as a non-turbo engine and thus not use more gas. I was wrong.

About the MPG quest. It’s not so much about MPG. It’s about fuel savings. Last year when gas was $4.25gal here E85 was $2.40gal. That’s a 44% savings. Again I’m talking here in MN, yes we make it, it’s government subsidized, it was that much cheaper here. A proper modification to Flex Fuel would pay off very quickly.

About modifying the car, ruining resale value. Look, I’m putting on 50k miles a year. After one year the car is only worth $14k from the miles. The car is not going to be worth anything in 6y years minimum I plan to keep it. A car 300,000 miles on it basicly is going to be worth Zero.

Many of my co-workers drive AWD Vans, or SUVs or even full sized pickups. I really am looking to do better MPG.

The Link provided doesn’t go directly to what I was pointing to.
I was pointing at the Eco-Tuned STi. The post is in the bottom half of that page. I figured they could do some thing simular to a WRX, with out emphasis on HP.

OK, so now you’ve made it clear, replacing the WRX is not an option. So most of the above posts are on target - forget the E85 conversion, you’re playing with fire with a WRX. I don’t worry about resale, I worry it’ll fry your engine. And the ‘turbos make power when you need it, good mpgs when you don’t’ line has never proven true in all the tests I’ve seen. All the 4cyl turbos test out at 6cyl mpgs when making 6 cyl power. I know of no good option to improve your driving costs with your WRX, besides slowing down and less-agressive driving. Sorry.

p.s.-I drove a GTI in Anchorage for 12 years, never got stuck, so you can deal with snow in a non-AWD vehicle, given good tires.

In addition to agreeing strongly with what the true experts have already posted (it’s unanimous, don’t use E85 in this vehicle), I’d also suggest that if you think E85 would save you money you first read this article. Oh. I also agree that spending $3K++ to try to sqeak a few more MPG out of a properly running engine…any engine…is folly.

I’m curious, you’ve bought a road-rocket and then detuned it for better mileage. Why did you spend the extra money for a road-rocket in the first place?

I only see bad talk about E85 economy using the enviromental desaster that is a GM SUV. I doubt that a small car would so such behavior. Also that truck is made to run at 87 octane, if you run way higher octan in a vehical you get less power and less MGP. What about a engine the likes high octane and also is tuned for it?

The problem is not the choice of an SUV. The problem is that E85 has about 30% less energy per gallon than gasoline, so your mpgs will typically be about 30% lower. It’s been tested multiple times. The only way around it (to a small degree) is to design an engine from the ground up to use E85. Such an engine could run a higher compression ratio, and lose less than 30%. Of course, such an engine would self-destruct if you put gas in it…

I haven’t done anything to it yet.
I answered the why in a large post above.

I have to repeat that in Minnesota and area states most gas stations have E85. And around here the price is far lower than all those South West state examples. I can understand if your in California and the next station is in Vegas one would be leary.
The price difference last year was $4.29gal for 87oct, and $2.40gal for E85, that’s huge!

I am listening to all the negative comments about E85.

The 2008 WRX is rated for 19 MPG city and 25 on the highway, 21-23 MPG right on the money as to what you should be getting. It is a performance car, and is no means “the best MPG car available that meets the criteria of AWD.” I’m sure there were plenty of other non-turbo Suburus on the lot, there at least a have dozen other AWD cars that offer equal or better mileage. But I’m thinking that you wanted something a bit quicker and cooler. Nothing wrong with that at all, but you must remember there will be tradeoffs.

I wouldn’t bother with the E85 package. The only thing on that list that may make a difference is mileage is the ECU tuning. The other stuff is just traditional go fast bits. For $3k it’s not a particularly good value either. I also highly doubt the claims that the car will get better fuel mileage on E85 than gasoline simply because a gallon of E85 has something like 30% less energy in it that a gallon of gasoline.

Still 23 MPG out of a 2.5L turbo I4 isn’t that good. I have a supercharged V8 Mustang that gets 22-23 MPG on the highway and it’s engine is nearly twice the size.

I interpreted the “Monday I reset the ECU” as a detuning. Perhaps “retuning for mileage rather than perormance” would have been more correct. If I’ve interpreted the statement correctly, that would be what improved your mileage rather than the K&N filter.