I'm getting 10-11MPG with a '91 N/A with 99,000kms with only an exhaust and HKS filter. I may WOT on a daily basis, and drive 100% city but that's still ridiculous. I got 10.7mpg on my last fill-up and 11.3 on this fill-up.

My 9000lbs '05 Diesel Ford gets 7mpg better than your car...yeah thats brutal lol, sorry to hear that

The car seems to be running great so I don't understand how it's possible. So I'm planning on replacing everything fuel related to see if it solves it. I may need to spend a few hundred dollars, but it'll save me in the long run. If I can get 5-10mpg more I could be saving 20-40 dollars every 8-14 days(when I fill up). I only got 20.5 MPG 100% highway averaging around 90kph.

Start with the basics. Plugs, plug wires, fuel filter, injector cleaning, air filter, ditch the cat or replace it

Is your 02 sensor good or hooked up?

I haven't checked if its good or even hooked up because I don't even know where its located. I also haven't been able to find an s5 o2 replacement that is plug and play, they all require wiring which im not capable of doing.

im ordering new wires and plugs tonight and will be replacing the fuel filter today as well. Car died on me when I started it this morning and it flooded slightly since I had to give it gas to start it and it smelled like gasoline afterwards. Im assuming new plugs and wires will help?

Just an update. I still get 10-12 mpg in the city but I got 28mpg on my drive home(to see family) averaged 100kmph, drove 320kms. Now this is the real kicker... I averaged ~32mpg on the way home during a huge snow storm. It took me 30 minutes longer but I also stopped for a bathroom break. I was one of the many who said it wasn't possible but you can't deny the fact I drove 300km and only used 22 litres of fuel. (187 miles and 5.8 US gallons = 32mpg).

My mind is blown. I was constantly slowing down and speeding up because of the random times where the snow was so bad I couldn't see anything at all.

Thats very interesting. I have the exact opposite problem, I get 18-18.5 mpg regardless of what I do. I can drive 70 mph on the interstate for 250 miles.....18.5. Or I can drive all city and romp on it and I get 18.3. I don't get it.

I'm using the simulated narrowband output from my Innovative WB O2, and the values look to be the same as the readings from the stock O2, so I don't think that's the problem. The problem seems to be that the milege doesn't improve on the highway like it should and the 02 sensor is the first guess, but that doesn't look like the case.

I wish I got 18mpg regardless. I only drive on the highway once a month at most. Other than that I'm never in 5th gear. I got back last night and drove 50kms since and already used up 1/4 tank of gas. Compared to when I got 300kms on a 1/4 tank. I will add to the fact that we got 6ish inches of snow over night and it's still snowing as I speak and the roads this morning where inches of slush and powder. I couldn't get grip if I tried, so my tires span all day. That and I went for a little drift around the Walmart parking lot at midnight, aha.

When I used to own a 97 Civic SI(Canada) with an automatic transmission I got 10-11km for every litre of fuel no matter how I drove, where I drove, etc. Always got 400-450kms per tank. I would get lucky every now and again and got near 500kms on a tank when driving from Sudbury to Toronto.

This is not surprising at all. It sounds like your o2 sensor is working just as it should. The only time the ECU will go into closed loop mode and conserve fuel is when you are driving at speed for an extended period of time (o2 sensor is used for this). If you cruise on the freeway for 100 plus miles and are smart with your right foot 30mpg is easy in a NA FC.

When you do all your driving in the city the ECU will never go into closed loop mode (o2 sensor is not used) and the ECU is always using the preset map for fuel and timing. The fuel map is pretty rich to start with.

Are you aware of the deceleration fuel cut the ECU does with the car in gear, the rpm's above 1500 and the throttle closed? Using that to your advantage will save fuel. A technique that would no doubt be used by accident at freeway cruising speeds without knowing it.

So if I am say in 4th gear doing 70km/h and there's a red light coming up or a stop sign, instead of rev-matching downshifts 'til 2nd gear then come to a stop or just put it in neutral until stop I could just let it slow itself down in 4th or 3rd until near stop and that would save fuel? I rev-match all my downshifts so I feel like that also uses more fuel considering the throttle blip. I know about the fuel cut during deceleration but I probably don't utilize it.

I'm getting 22.5 on the highway

I always decel in the gear until it gets down to 1500 rpms then shift into neutral. If you are deceling in 4th you will lose speed less quickly than if you were deceling in 3rd and therefore travel further without using any fuel. If you pay attention you can really take advantage of the fuel cut.

I'll take advantage of this and report with results. Because of this shitty weather I've done 65kms and used up 1/3 of a tank.

I have a GTUs gas 0 dead battery and neds a rebuild

More info on your setup? I was thinking of trying this on my old haltech, but I'm not sure where to start.

Im getting about 220 miles a tank in my s4 n.a. Most i ever got was 240ish. It has a full tune up but i havent cared enough to look into it further.

I am curious about one thing though. Since im running 17's that throws the speedo off calibration slightly so how bad could it affect my trip meter?

^-----Depends on your tire size. I have 18s, but I picked up 35 sidewalls to keep the speedo accurate. 17s should use 40 I believe. I know the weight of the 18s affects me too... but I cant comment on how.. I just know it does, it feels like it. Wheels+tires=about 30lbs a corner. ooof.





I got an app on my phone, I just punch in numbers and let the machine take care of it. No user error.

With that being said, I still wonder if something is wrong with my car, or needs ANOTHER major tune up... I dont know...

Totally bone stock.
Highway car only.
Always keep it under 3500-3800 RPM
Mostly cruise to save on gas, but I definitely get wild hairs up my butt often... (When you come up on more than one LARGE sweeping high speed slope on a deserted highway, it's really hard to not find 3rd gear and hit 120+ before you even enter the turn...)

(Remember that I have GTUs gearing... I get limited by how fast I can actually drive with this mindset, I dont want to open up the 2nd ports.)

app says the last 3 months average came out to 17.257mpg. Last month was 17.318. I started getting 18.5mpg for 3 tanks, but the last 3 fillups came out to 16-17mpg... Maybe my driving changed.

Says I get 320 miles a tank, and it cost me $70 a day to own this car. My daily has the same size tank and EASILY gets 400-420 a tank.

Something is wrong with my car(s), lol.

I keep it under 3800rpm 90% of the time, I bring it past to get the secondary injectors to come in every so often and redline every here and there for carbon build up. I get 10-12mpg city still. Even though as I posted earlier I got 28mpg highway on the way home and 32mpg on the way back.

I honestly don't think there's a damn thing we can do with these cars economy wise. They're rated at what, 18mpg city? If you're getting 16-18 city I'd just be happy there.

We just got a lot of snow here and therefore the roads have been covered for a few days so because I went drifting for a bit and my tires spin often trying to accelerate from a stop so I've done 170kms and I'm almost at 1/4 tank left.

20mpg highway

Small port, BNR4, Wolf3d, and 91 octane

I get about 20mpg in my '88 N/A

I get a steady 20mpg, mixed driving. I don't drive hard on the street, but then i don't try to get low mpg's either.
Lowest i have seen was 24mpg on a full tank.

Oh and the car is a 86 with stock S4NA engine, emissions removed and free flowing exhaust. Weighs in at 1200kg wet.

my fuel mileage is ∞ because it doesnt run

I have a stock 1988 N/A se and I get 17 city 28 highway

10mpg on an agressive streetport with a gt4088 and big injectors (1200cc primary, 1680 secondary)..... too big but its what came in the car, so its what i am running. tunning with an e6x