Hi all,

I have a 55 reg mk2 focus 1.6l petrol automatic gearbox. My mpg dropped a bit so I've cleaned out the throttle body and MAP sensor. 

Throttle response now feels smoother, and my mpg has risen a little bit but still not where I would want it. 

Thermostat and housing have recently been changed, along with the radiator hose, spark plugs, and front tyres, and a bit before that (3k miles ago) car had a service. 

What else can I do to improve the fuel economy? Looking for things that are basically free to do (like cleaning parts that get clogged up) or cheap (potentially get a new MAP sensor?). 

Below is before and after photos of my throttle body cleaning. 

Frankly I'm not after the best-in-business restoration, I just want a reliable car and to save money which I can spend on my daughter. 

 

Run it on E5 Super unleaded, Tesco is good value

Have it de-coked

Change transmission fluid and stick some of this in when you refill

https://lubegard.com/products/platinum/

On the fuel theme, there is an Archoil for petrol (gets premium fuel at less than the fuel station difference - work it out, but won't get rid of the E10 -E5 bit?)

I think "WE" rate the diesel version (don't expect much in the way of massive, if any MPG improvement) but I don't know about any experience of the petrol?:
https://www.amazon.co.uk/Archoil-AR6900-P-Advanced-Petrol-Synthesis/dp/B0727XC5BR?th=1

Yeah, I've not seen much about the Petrol one, because I only bother with the Diesel one.

The Diesel one is fantastic though

2 hours ago, DaveT70 said:

Run it on E5 Super unleaded, Tesco is good value

Have it de-coked

Change transmission fluid and stick some of this in when you refill

https://lubegard.com/products/platinum/

Lovely thanks, I'll have a look at this 

 

1 hour ago, Shearers said:

On the fuel theme, there is an Archoil for petrol (gets premium fuel at less than the fuel station difference - work it out, but won't get rid of the E10 -E5 bit?)

I think "WE" rate the diesel version (don't expect much in the way of massive, if any MPG improvement) but I don't know about any experience of the petrol?:
https://www.amazon.co.uk/Archoil-AR6900-P-Advanced-Petrol-Synthesis/dp/B0727XC5BR?th=1

Thanks hadn't heard of this 

I have now filled up with E5 with a fuel injector cleaner additive thrown in. We'll see what difference, if any, it makes. I usually run on E10 so no idea what to expect. 

Cold weather will also make the fuel economy drop. Get your intake and valves de-coked looking at the buildup on your throttle body, they will be being chocked by the carbon.

20 minutes ago, Neb_engineer said:

Cold weather will also make the fuel economy drop. Get your intake and valves de-coked looking at the buildup on your throttle body, they will be being chocked by the carbon.

Thank you. Had never heard of this. I'm sending enquiries to some places. What would you reckon this type of thing would normally cost? Also what type? Walnut blasting?

On 12/19/2025 at 2:31 PM, Eli_P said:

I have now filled up with E5 with a fuel injector cleaner additive thrown in. We'll see what difference, if any, it makes. I usually run on E10 so no idea what to expect. 

Your car is way, way too old for E10 anyway

UPDATE: Bought an OBDII reader and it found no faults, so I wondered if a more rigorous clean might be in order. Got some more throttle body cleaner and managed to get off even more grime from throttle body and MAP sensor. 

Plugged code reader in again after idling the car for 10 mins and still no faults. All good. Topped up petrol with more E5. 

Drove 60 miles home from my Moms house (I don't have private driveway to do work on but she does), and my mpg has shot up to 37 over that distance. I have personally never seen this car do more than about 28 previously no matter how many motorway trips I did to get the engine up to temperature. 

Throttle response feels fantastic compared to before the repairs I listed in the initial post on this thread. 

Couple of questions: is 37mpg over 45 miles of motorway and 15 miles of urban roads any good for this particular car? 

What's the chances of there being more very cheap tinkering I can do to push it closer to the 40mpg mark? 

2 hours ago, Eli_P said:

UPDATE: Bought an OBDII reader and it found no faults, so I wondered if a more rigorous clean might be in order. Got some more throttle body cleaner and managed to get off even more grime from throttle body and MAP sensor. 

Plugged code reader in again after idling the car for 10 mins and still no faults. All good. Topped up petrol with more E5. 

Drove 60 miles home from my Moms house (I don't have private driveway to do work on but she does), and my mpg has shot up to 37 over that distance. I have personally never seen this car do more than about 28 previously no matter how many motorway trips I did to get the engine up to temperature. 

Throttle response feels fantastic compared to before the repairs I listed in the initial post on this thread. 

Couple of questions: is 37mpg over 45 miles of motorway and 15 miles of urban roads any good for this particular car? 

What's the chances of there being more very cheap tinkering I can do to push it closer to the 40mpg mark? 

For the carbon clean out you can use 2 stroke red oil in with your fuel.. with yours being a petrol id only go with a 500ml/half litre every 2nd time of filling l did it with my partners Y reg 2.0 vw n it went a lot more better after a few uses. I constantly use it in my diesel van, air filter is another good bit to do if not been done.

Edited December 22, 2025Dec 22 by doggsbody

I would say you are likely now chasing small returns and to me a genuine 37 MPG on a run with a 1.6 petrol auto is pretty to very good?
Of course everyone will now come back with their 50 MPG plus results! 😉
I'd be interested in the carbon cleaning prices but suspect it may not be worth it unless you don't mind spending loads on an old vehicle which now seems to be running well?
Oh, and Forscan may show up codes that an OBD reader doesn't even see so need to be aware of that.

2 minutes ago, Shearers said:

I would say you are likely now chasing small returns and to me a genuine 37 MPG on a run with a 1.6 petrol auto is pretty to very good?
Of course everyone will now come back with their 50 MPG plus results! 😉
I'd be interested in the carbon cleaning prices but suspect it may not be worth it unless you don't mind spending loads on an old vehicle which now seems to be running well?
Oh, and Forscan may show up codes that an OBD reader doesn't even see so need to be aware of that.

I'll take that then. Time to stop chasing results and just enjoy the thing 

1 hour ago, doggsbody said:

For the carbon clean out you can use 2 stroke red oil in with your fuel.. with yours being a petrol id only go with a 500ml/half litre every 2nd time of filling l did it with my partners Y reg 2.0 vw n it went a lot more better after a few uses. I constantly use it in my diesel van, air filter is another good bit to do if not been done.

Thank you, I do like a DIY carbon clean as opposed to professional services for this old car 

2 minutes ago, Eli_P said:

I'll take that then. Time to stop chasing results and just enjoy the thing 

That's just me, others may give encouragement to continue! With 2-stroke, likely be ready for smoke! 😀
A regular service to manufacturers recommendation would likely help.

2 minutes ago, Shearers said:

Of course everyone will now come back with their 50 MPG plus results! 😉

I used to get way more than that in my 2.5 diesel banana engine.. but l was using straight forward bio fuel 😂 l could use the same amount of bio as norm n the bio would last nearly double the straight. But that was bio made by a man with a PHD in chemistry long gone those days though he had a stroke n had to give it all up the poor guy ☹️..

3 minutes ago, Shearers said:

That's just me, others may give encouragement to continue! With 2-stroke, likely be ready for smoke! 😀
A regular service to manufacturers recommendation would likely help.

No it's not encouragement to keep chasing that extra just a way of cleaning the carbon out without the massive exspence.

FINAL UPDATE: Needed a new blower fan resistor because my air conditioning didnt work on settings one or 2. Only place I could find it in stock was GSF Car Parts in Stoke on Trent (I live in Birmingham). Went this morning and fitted new resistor, A/C now works beautifully. 

Mpg on way home was 40mpg. For a 20 year old automatic car, I'm not going to expect anything better.

I think my project is now completed.

Thanks for your tips everyone.