What did improve the fuel economy for you?

[tjts1]

I've been through and achieved an automotive degree, so when I hook up a scanner which will read live data, I can see that the fuel trims are slightly off, but not alarmingly. The O2 sensor seems to be putting out the proper average voltage ( 0.45v) but I can't see how fast it switches, so Im not sure how old or new it may be. With the average being about right, I would imagine that it's working OK. MAF sensor, thats also something which seems to work properly with throttle position change. I can see the flow through the MAF increase numerically on the scanner as I press the accelerator.

What is your LTFT? Mine was at -9.4% a few months ago when i first got the ELM327. A month after changing my O2 sensor it was at -10.2%. Almost wish I had a WBO2 on this car. Both the old and new O2 sensors seem to switch kind of randomly. It never seems to sit near 0.5v. Its always at < 0.1 or 0.9v. The only time I've ever seen a true switching patter was at idle with the engine fully warmed up. I'm tempted to put a WBO2 on this car just to see whats really going on.

[rspi]

If I were you, I'd run 3 tanks of 91+ octane and see if it changes on the last tank. These computers lag with adjustments sometimes. Running 87 does retard the timing to aviod knock. If I had a NA, I would NEVER run any gas under 91+ octane rating.

I really can't imagine why you are getting low fuel unless you have aftermarket spark plugs in the car. I tried that once and within a week noticed my mileage under 20mpg. The other day I got 25 around town.

The single most productive thing I did to help my gas mileage was to purchase a www.ScanGauge.com.

[tjts1]

I've seen many tanks in the low 30s on the highway and mid 20s in the city on 87 octane. The only time it drops below that is if it spend a lot of time in stop and go traffic. As long as the engine is not pulling timing, whats the point of paying for more octane?

I'm just curious to see what others are getting on their LTFT. I just took another look at it just now and its showing -10.3%.

[RDEJR]

I will have to take a look again at LTFT.

I have a set of NGK Iridium plugs in it right now, that's what was in it when I got it. Being that they are iridium, they are supposedly "non-adjustable" gap, and are currently at .040". Should I gap the iridium plugs to .028" like the copper plugs should be, or is there another plug that I can get which is the same-ish as the original Volvo plug?

I'm wondering if that may play a small part, and I know the spark plug topic is like a can of worms. If I were to go Autozone, and I decided to buy standard copper plugs and gap them to .028", what would they be? Bosch Super Copper?

.028" seems incredibly small... I'm accustomed more to older rigs where you start at .035" and go up from there depending on your ignition system.

[asimba2]

According to fueleconomy.gov, the turbos are rated at 17/24 mpg, non-turbos at 18/26. I am finishing up Stage 0 (just need to check spark plug gap as the last item on the list) and I average 25-26 mpg highway with my turbo, which is 1-2 mpg higher than the rating. In the city though I get 2 mpg less, at 15 mpg. It's so hard to compare mileage between cars, but I KNOW why my city mileage is so low. I cold-start the car, drive 1.8 miles to a park and ride, shut it down just as it has come up to operating temperature, then I do the exact same thing going home from work and again between the gym and home. When the engine is not warm the ECU is still in open loop mode and the air/fuel ratio is richer than normal. For every mile PAST the 1.8 mile commute, my average mileage starts to increase because now the air/fuel ratio is where it's intended to be. My point is, keep your tires inflated, keep the engine in tune and drive reasonably, your mileage is what it is.

I can increase my average MPG if I take a longer route to work, but I've burned more fuel in the end. I have also found that accelerating at a very slow pace does not save fuel compared to accelerating at just a normal rate. It's basically the difference between 10 MPG for 10 seconds of acceleration or 5 MPG for 5 seconds (or whatever)...as long as my acceleration isn't pedal to the metal, I can't measure a difference in economy between normal acceleration and agonizingly-slow-tick-off-the-people-behind-you acceleration.

And for what it's worth, ethanol has had the biggest negative effect on my mileage due to its lower BTUs compared to gasoline. And joy oh joy, it's also eating our rubber fuel hoses like nobody's business.

Coroplast
http://farm4.static.flickr.com/3150/269 ... 11f1_o.jpg
http://farm4.static.flickr.com/3288/269 ... 6eb1_o.jpg
http://farm4.static.flickr.com/3245/268 ... eb75_o.jpg

Regarding this, did you notice an improvement in economy? I would think that would make a difference.

[rspi]

Volvo estimate of fuel mileage, when these cars were new, was 18/24 T5, 19/28 N/A. So the FuelEconomy.gov is about right, especially since people are putting their actual numbers in there.

If you drive less than 10 miles then let the car sit for more than 3 hours, etc., I'm surprised you get more than 12 mpg. You have to drive the car up to temp before it will get it's rated mpg.

@ RDEJR: Man, your problem are your plugs. Don't buy AutoZone, Bosch, or any other plugs, get OEM Volvo plugs. Heck, the plugs you have probably cost more. Drop those OEM plugs in there and start saving money. If you get 10% better gas mileage, you will pay for the plugs in 3 tanks of gas. On the highway, you will likely jump about 30% - 50% of your mpg and heck, those plugs will pay for themselves in 1 tank of gas. I pulled a set of NGK's out of my 960, installed some OEM plugs and went from 21 mpg to 25 mpg. There may have been a few other factors involved but I was driving like you. Like an old lady. Get those plugs changed and you'll hug yourself at night.

I do agree with Asimba a little about the passive gas pedal thing, especially if you have a turbo. But you do what to keep the throttle a little low. I drove passive one tank and agressive the next and it didn't make much difference, maybe 1 mpg. Now the thing that does make a big difference is some hypermilling techniques. Taking my foot off the gas 10% sooner coming to a light saves gas. My ScanGauge II really helped me actually see those differences.

[rspi]

Here are the plugs you need: http://www.ipdusa.com/products/4878/113 ... k-plug-set

[s70glt novice[Will]]

With the exhaust (stock other then that) i gained 1-2 mpg. With my ARD Green, i now get 15 mpg. (dont worry, i think we all know why ) The wires, plugs and cap and rotor helped ALOT.

IMO, get a "tune up" kit from FCP Groton. Worth it for not having to hunt down all the parts.

[tjts1]

Coroplast
http://farm4.static.flickr.com/3150/269 ... 11f1_o.jpg
http://farm4.static.flickr.com/3288/269 ... 6eb1_o.jpg
http://farm4.static.flickr.com/3245/268 ... eb75_o.jpg

Regarding this, did you notice an improvement in economy? I would think that would make a difference.

On the highway, definitely. It was well worth the effort.

RDEJR
Lose the iridium plugs. Get the volvo plugs or NGK equivalent copper core. Gap to spec. 0.28 is spot on.

[erikv11]

I will have to take a look again at LTFT.

I have a set of NGK Iridium plugs in it right now, that's what was in it when I got it. Being that they are iridium, they are supposedly "non-adjustable" gap, and are currently at .040". Should I gap the iridium plugs to .028" like the copper plugs should be, or is there another plug that I can get which is the same-ish as the original Volvo plug?

I'm wondering if that may play a small part, and I know the spark plug topic is like a can of worms. If I were to go Autozone, and I decided to buy standard copper plugs and gap them to .028", what would they be? Bosch Super Copper?

.028" seems incredibly small... I'm accustomed more to older rigs where you start at .035" and go up from there depending on your ignition system.

To beat a dead horse: get rid of those plugs. I've been driving a 96 NA for 10 years, these two plugs give identical (excellent) performance: Bosch coppers at 0.028 or Volvo only. The Bosch are much cheaper and you can buy them at Autozone, they just don't last as long as the OEM ones ...