Ive only had my A4 for a week and a half, but I think Ive pretty much learned to drive it as easy as possible. Right now its telling me Im averaging 23.7 mpg. When I got it, it said 18.8? I believe, so I know Im easier on it than the previous owner. Coming from a truck, this is better than I ever dreamed of getting, but Im still curious what can be done (besides driving style) to increase mileage? I really dont care about improving power, I think its more than quick enough at the moment. EDIT: Read a couple of other posts, and one said that if the temp sensor is blitzing it will affect mileage. That would make sense, because some days it doesnt work at all, it just stays all the way to the left. The owner before told me that the car just wouldnt start one day, and the mechanic told them it was because the sensor was bad and started dumping fuel into the car, causing a loss of compression. So Im guessing they just pulled the plugs, drained the gas, and replaced them, but didnt replace the sensor. What does this part cost, and is it something I can do myself easily? Im fairly savey at mechanical work, but Ive always had american cars, so this is a little new for me. Also, can someone post a good tutorial for running seafoam through our cars?

 

year engine and tranny?

 

k&N intake. exhaust. some good looking headlight sometimes help improve gas mileage. haha. what year and model do you have

 

its in my sig. I went to autozone and had my codes checked, it threw us PO431 and a PO1423. whats to make of that?

 

haha sorry didnt even see that.


P0421 = warm up cat converter bank 1 below efficiency threshold possible causes are bad cat/ wiring/ HO2S sensor ( o2 sensor )
P0431 = bank 2 same problem

 

There are plenty of posts on this forum for seafoaming a 2.8, just gotta search around, thats how I found them

As for mileage improvements, I've gained about two to two and a half MPG from modding my airbox (a poor man's cold air intake system that has undoubtedly been just as effective, and in my opinion, better for the K&N since the filter is still housed so it doesnt run a risk of getting wet like a cone filter used on the typical CAI) so you might try that (theres a DIY in the DIY section on the main AF page) that explains quite effectively how to do the mod (its pretty simple anyway, and since you said you're pretty mechanically savvy, I doubt you'd have a problem with it)

another way to boost the mileage is, as you said, driving style. I picked up another one to two MPG by shifting quickly to keep the RPM below 2k, not accelerating hard, and by going the speed limit, which, contrary to popular belief, enables you to hit more green lights which requires you to stop less which we all know that stopping and going all the time is probably the biggest negative affect on gas mileage.

also, if you commute on the freeway alot, you might try (though i dont recommend this because of it's elevated level of you-might-end-up-killed factor) but you might try drafting, which involves getting behind a large vehicle, typically an 18 wheeler, and staying within 5-10 car lengths of it. at the higher speeds, the air is somewhat 'sucked along' behind the big rig at a close distance, and if you're in that backdraft, it pulls your car along with it, which can boost your mileage by about 40%, or so the msn.com article on 'hypermiling' claims, and 'hypermiling' is exactly what all these techniques are called these days, the aforementioned msn.com article (which had people reporting claims that they were drawing 60+ mpg out of a factory-rated 25 mpg car) is my source for all that i just paraphrased and though i havent tried the drafting yet, the other techniques that i mentioned first have had a definite impact on my mileage so its definitely worth adjusting the speed demon in us all to suit the rising necessity to see to it that a tank of gas will go as far as possible.

and lastly, while poking around in autozone the other day, i came across a small non-moving device called a tornado which, next time i have an extra fifty bucks and an hour of time, i will be purchasing and installing one. essentially, what that does is cause the incoming air to spin like, well a tornado, and the agitated, fast moving and spinning air causes the injected fuel to atomize more so that when ignited, you get a more complete combustion, which reduces hydrocarbon emissions and improves gas mileage 1-2mpg (so the package says) and i figure its worth a try, it must work since the package had a security cable around it. it just mounts right after the MAF so installation should be pretty basic. once i get one installed, ill post up and let everyone know how its working out.

 

Due to the codes, definitely look into O2 sensors. Also, you can add a few psi to your tires for lower rolling resistance. Get some good electrical contact cleaner and clean the connectors for all of your sensors (or as many as you can reach). If you haven't ever done so, clean the throttle body. Do a full Seafoam treatment on your car (oil, vacuum, and fuel). Take excess crap out of your car (all that miscellaneous stuff in your trunk, for example, if you have the pack-rat look and are carting all kinds of stuff around). All of those, plus the other suggestions, can combine to give you some decent mileage improvements.

 

when you got the codes scanned, did you have a cel on? if not, nothing should be wrong. if you get the cel for the same codes then it's time to replace the 02 sensors. also do a seafoam treatment. as for the tornado, it's useless on our cars unless you take everything apart and put it right in front of the throttle body. if you put it in the solid hose on the farther end to the throttle body, the air will lose velocity by the time it reaches the throttle body. i actually made one out of stainless steel but it was a crappy one so i'm gonna make it better and put up some pix and see if the mileage gets better

 

Another idea - buy new plugs, make sure they're gapped correctly, and install them. If yours have been in there a long time, it's unlikely they're working at peak efficiency. New ones can boost your mileage somewhat.

Hiwords, sorry I missed your call last night - was putting in the front springs. Job is done, height is a bit lower (not tremendously, since I think the strut height is the main determiner of ride height) but it is somewhat lower, the ride quality is firmer, cornering is flatter, and the reflexes are sharper. You should see the difference in beefiness though - the new ones must be 1/8" thicker. My impact gun was actually having to work hard to compress them enough to get them on the struts! Overall, a great budget upgrade.

 

The cel has been on for about 2 years according to the person I bought it from (I didnt notice it when I test drove it, its tiny). She said that the mechanics couldnt figure out why it was on, but she never had problems with it. I did a carfax report last week, and saw that it failed emissions at 75k, and then it was serviced, and passed a few days later. It was still under the 80k warranty at that point.

As far as 02 sensors go, what can I expect to pay for them and is it an easy job or will I have to set time aside for it? Same thing with the plugs. The manual says I need to use plugs from Audi only? I would like to put in platinums but I dont know what plugs the 2.8 really does the best on. And it looks like I have to remove the fuel lines to get the plugs out?

Ive done plenty of repairs on my previous vehicles (in fact, they never went to the shop), but they were all ford trucks so it was a different monster.