S197 S/C'd 4.6........MPG

[UK-Stang]

A question for all S197 owners with a S/C'd 4.6 3V:

What is your average MPG when motorway cruising at 70MPH?

I have had a consistent decline in my MPG over the last year or so and it's not due to any 'spirited' driving! I used to get between 23-25MPG when cruising at 70MPH and I am now barely getting 17MPG, the plugs, oil, filters etc have no more than 1200 miles on them and I use Shell VPower unleaded.

Before I had her S/C'd I used to get about 300 miles from a tank and of course I realise that once the blower went on and I put 3:73 gears in that wasn't going to stay the same so it droped to about 270ish. However, now I get about 190 miles from a full tank!!!

I realise that any 'dropping the foot' action has a huge effect so that is why I'm only looking at motorway driving. In towns I get about 10-12 MPG.

I'm stumped as to why it's so low.....or is it?

Any comments/suggestions welcome!

Cheers,

 

[skwerl]

On the highway I can get 20+ mpg if I keep my foot out of it. I averaged 19.9 on my trip to Tampa and back a couple weeks ago when I went to have lunch with Kelly (BMR Tech). Around town I seem to average about 13-14. Taking off from stop lights uses a lot of fuel.

Also, are you measuring in American gallons or Imperial gallons? They are not the same so comparisons can be skewed if most of the commenters are not aware of the difference.

 

[chandlern]

On the highway at 70 usually around 23-25mpg, in town anywhere between 10 and 19 depending upon how I drive. Theres quite a bit that could lead to the drop in mpg, trans, rear, dragging a caliper, etc.

 

[RED09GT]

A friend of mine's car had a similar problem. He reflashed the tune and his fuel economy got back to where it had previously been.
Also, are you running an oil catch can or separator? If not, the oil buildup in the manifold and intake ports may be part of the problem.

awesome autocorrect malfunctions brought to you by tapatalk

 

[bcb06gt]

O2 sensor maybe. If its reading is slightly off (biased), then an increase in fuel could be being called for during cruising.

 

[marcspaz]

Bro... I had a heavily modified NA 4.6 that only got 8-9 MPG Consider 10 or 12 good.

You can try to do a reflash and relearn to clear your tables and let the computer realign itself. Some times the adaptive tuning gets out of whack if the tune changes dramatically or frequently in a short time period.

Do this...

Drive your car until it is at normal running temperature.

Disconnect the battery for about 10 minutes.

Reconnect the battery, but don't start the car.

Reflash the car with your tune.

With the vehicle at a complete stop, set the parking brake.

Put the gearshift in position P (automatic transmission) or the neutral
position (manual transmission), turn off all accessories and start the
engine.

Run the engine until it reaches normal operating temperature again

Allow the engine to idle for at least one minute.

Turn the A/C on and allow the engine to idle for at least one minute.

Drive the vehicle to complete the relearning process. The vehicle may need to be driven 10 mi (16 km) or more to relearn the idle and fuel trim strategy. If you do not allow the engine to relearn its idle trim, and fuel trim strategy, the idle and drive quality of your vehicle may be adversely affected until the trim is eventually relearned.

After you drive the car for about 10 miles, turn the engine off and reset your fuel economy data to zero and then go for a ride. See if it improves.

 

[Mattamus]

I have a little m90 with 4.10 gears. I get around 20-21 @70 driving from SoCal to NorCal regularly. I only get about 12 in town but that is a direct result of my occasional lead foot.

 

[UK-Stang]

Thanks for the help guys, I'll give a reflash of the tune a go a go!

 

[VectorPat]

I only get about 19 at best on the hwy, city is probably around 13-14

 

[808muscle]

All my driving is city style, m90, cams, auto, 4.10 gears and a heavy foot. I'm lucky if I get 160 miles on a tankful. My other two vehicles get 8-9 mph so the stang is mpg friendly in my eyes.

 

[Five Oh Brian]

My '07 GT automatic had a Vortech S-trim blower, 4800 rpm stall, and 4.10 gears. Only got about 11 mpg city and around 21 mpg highway (at 70 mph). At 60 mph, mileage was better at 23-24 mpg on flat ground.

 

[BruceH]

A question for all S197 owners with a S/C'd 4.6 3V:

What is your average MPG when motorway cruising at 70MPH?

I have had a consistent decline in my MPG over the last year or so and it's not due to any 'spirited' driving! I used to get between 23-25MPG when cruising at 70MPH and I am now barely getting 17MPG, the plugs, oil, filters etc have no more than 1200 miles on them and I use Shell VPower unleaded.

Before I had her S/C'd I used to get about 300 miles from a tank and of course I realise that once the blower went on and I put 3:73 gears in that wasn't going to stay the same so it droped to about 270ish. However, now I get about 190 miles from a full tank!!!

I realise that any 'dropping the foot' action has a huge effect so that is why I'm only looking at motorway driving. In towns I get about 10-12 MPG.

I'm stumped as to why it's so low.....or is it?

Any comments/suggestions welcome!

Cheers,

O2 sensor maybe. If its reading is slightly off (biased), then an increase in fuel could be being called for during cruising.

More than likely it's the o2 sensor since it was better at one time and slowly went down.

Can you datalog your fuel trims? My guess is that both ltft and stft are high and adding fuel that doesn't need to be there.

 

[UK-Stang]

More than likely it's the o2 sensor since it was better at one time and slowly went down.

Can you datalog your fuel trims? My guess is that both ltft and stft are high and adding fuel that doesn't need to be there.

Both O2 sensors are new....only done 300 miles since replacing them.

 

[lostsoul]

winter blend?

 

[BlackWidowStang]

20+ on the highway. I stopped keeping track in the city.

 

[tigerhonaker]

My MPG was somewhere around 17-18 MPG at 70 MPH with cruise set.

But if I messed around any at all it dropped instantly.

In the City probably around 11-12 MPG with stop and go situations and heavy traffic.

Terry

 

[scramblr]

I've squeezed 17mpg on the highway. Avg is 14mpg though.

 

[Swarzkopf]

Same thing used to happen with mine - it was adaptive fueling still enabled in my tune. I guess it's there to net you better gas mileage in the long term, but it was actually ruining mine. I disabled it. Now I get a steady 13/14 MPG in traffic driving and have gotten as high as 23 on the highway. Not spectacular, but I think it's decent for the power the car makes.

 

[b00stedgt]

I Have A Similar Set Up And See Around 12 For Local Driving And 19 For Highway.

 

[johnnyv8]

OP, who tuned your car? I know when I got my car tuned the first time by a local tuner, he kept it really rich to keep it "Safe", but the car drove like shit and got terrible gas milage. Since I got Lito tune, the car drives a whole lot better and I get about 250ish to the tank, not bad for the way I drive.