Can somebody work out the MPG of my car???

andy_fozzy

andy_fozzy

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Recently had the air con fixed in my car.
Some of you may recall my thread about it.......
Anyway, it turned out that the compressor was faulty. Had it replaced for a new one for £380 all in.
The last muppets wanted £650 + VAT :eek:

Anyways, going by advice on the a/c thread, and the chap who fitted it, I should keep the a/c on ALL THE TIME.
Fine by me, but I'm a bit concerned that it will use more fuel.

So, I put a full tank of juice in, reset the clock and kept the a/c on at all times.

I don't know how to tell if my results are good, bad etc.

There was £50 of diesel in the tank.
I done 410 miles, mostly motorway and I have dropped my speed allot.
(I used to wang along at 85-90 mph but now rarely go over 70)

Obviously I don't expect exact answers, as I cannot be exact on the price of the fuel at the time, EXACTLY how much was in there, EXACTLY how many miles.........

Just a rough-ish idea would be great :thumbs:
 
To work out mpg you need to know the volume of fuel used, i.e how much fuel went into the tank after the 410 miles....

Then divide 410 by the volume of fuel (assuming fuel is in litres) that will give you miles per litre.

Multiply that answer by 4.55(ish) to get miles per gallon

Simples ;)
 
You need to refill the tank, take a note of the cost per gallon/ltr, the total paid and the total mileage you have done, then it can be worked out!
 
TinaC said:
To work out mpg you need to know the volume of fuel used, i.e how much fuel went into the tank after the 410 miles....

Then divide 410 by the volume of fuel (assuming fuel is in litres) that will give you miles per litre.

Multiply that answer by 4.55(ish) to get miles per gallon

Simples ;)
Click to expand...

Eh???
AFTER the 410 miles?

Well I put another £40 in this morning :D
 
or the average extra consumption is anywhere between 2-8% extra with your A/C on. Most A/C fitters recommend that it is use it least for a few minutes every week, it is only to keep the lubricant in the A/C moving and not letting the seals dry out then losing the refrigerant

Dave
 
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The guy is right, you should actually run your AC full time.

I run mine full time and notice no difference, although at 13MPG it hardly matters does it! :lol:

If you are worried about loosing 1-2MPG or so though, just make sure you use it frequently - especially during Winter.

Can't help regarding calculations as I'm useless at maths. :D
 
Cheers guys.

So would you say his sounds about ok?

I haven't noticed much of a difference TBH.
And I'm not worried about it. Just curious!
 
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How much you spent putting the fuel in is only necessary should you want the cost per mile....

The method is, fill tank take no notice of amount just wince at cost. Run car as usual. fill tank again, notice volume of fuel and miles travelled. Use these figures as above.

miles x 4.55
volume
 
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TinaC said:
How much you spent putting the fuel in is only necessary should you want the cost per mile....

The method is, fill tank take no notice of amount just wince at cost. Run car as usual. fill tank again, notice volume of fuel and miles travelled. Use these figures as above.

miles x 4.55
volume
Click to expand...

Ah ok, thanks allot.
Might give that a go later :thumbs:
 
what car is it ?

i dont notice any difference with mine whether a/c is on or off
 
On-off switch? Yes, is that unusual.....????

It's a Focus 52 plate, 1.8 tddi
 
mrgas said:
mines a 1.6 tdci focus , like i said it doesnt appear to make any difference with air con on
Click to expand...

So far so good with me too.
A full tank lasts about a week, which it did last week with a/c on.

:thumbs:
 
Fill your tank, give me the car and we'll see how far I get before it runs out of fuel, mpg = amount in tank divided by how far I get :)
 
andy_fozzy said:
On-off switch? Yes, is that unusual.....????

It's a Focus 52 plate, 1.8 tddi
Click to expand...

i have worked it out to about 45mpg which is about right on one of these
are you sure its a tddi and not a tdci as they did not use the tddi engine for long
 
andy_fozzy said:
Anyway, it turned out that the compressor was faulty. Had it replaced for a new one for £380 all in.
The last muppets wanted £650 + VAT :eek:
Click to expand...

Ford said the same to me when mine went tits-up last year, but then the guy whispered confidentially that I'd be better off sourcing the parts privately and getting another garage to do the work... lol

Finally got round to sorting it last month: new compressor and condenser cost me £38 and £22 respectively, with new parts bought off ebay and the work (inc. 12-hour pressure test and full re-gas) cost me £150 at a garage near my dad's in Devon...:thumbs:

Most car manuals state you should run for at least 30 minutes per month, but weekly use is recommended especially in winter months, which is when most people forget to use it - it doesn't have to be set to 'cold' for the fluid to circulate... mine comes on automatically when I selct 'de-mist' - which is nearly all the time when it rains or during cold spells...
 
Arkady said:
mine comes on automatically when I selct 'de-mist' - which is nearly all the time when it rains or during cold spells...
Click to expand...

I could never figure out why Fords do that, why would you want ice cold air blowing on a window to de-mist it?
 
It's not just cold air, it's DRY cold air and it's the DRY bit that clears the screen.
 
Nod said:
It's not just cold air, it's DRY cold air and it's the DRY bit that clears the screen.
Click to expand...

:thumbs: Exactly...

...one more time - it doesn't have to be set to 'cold' for aircon to work - it also dehumidifies the air, especially if you select 'cabin' as opposed to 'outside' for the intake option...
 
Arkady said:
Ford said the same to me when mine went tits-up last year, but then the guy whispered confidentially that I'd be better off sourcing the parts privately and getting another garage to do the work... lol

Finally got round to sorting it last month: new compressor and condenser cost me £38 and £22 respectively, with new parts bought off ebay and the work (inc. 12-hour pressure test and full re-gas) cost me £150 at a garage near my dad's in Devon...:thumbs:

Most car manuals state you should run for at least 30 minutes per month, but weekly use is recommended especially in winter months, which is when most people forget to use it - it doesn't have to be set to 'cold' for the fluid to circulate... mine comes on automatically when I selct 'de-mist' - which is nearly all the time when it rains or during cold spells...
Click to expand...

JESUS Rob :eek:
Where did you get a new compressor for £38???? :suspect:
 
Arkady said:
:thumbs: Exactly...

...one more time - it doesn't have to be set to 'cold' for aircon to work - it also dehumidifies the air, especially if you select 'cabin' as opposed to 'outside' for the intake option...
Click to expand...

Indeed.

The chap who fixed mine said that the cold air is a bi-product of air conditioning.
The idea of air con is the de-humidifying.
 
terryuk said:
i have worked it out to about 45mpg which is about right on one of these
are you sure its a tddi and not a tdci as they did not use the tddi engine for long
Click to expand...

Yup.
Deffo the tddi.

Although I haven't a clue what the difference is :D
 
Steep said:
I could never figure out why Fords do that, why would you want ice cold air blowing on a window to de-mist it?
Click to expand...
My quick demist (Mondeo mk3) comes out luke warm not ice cold and clears the front screen in just a few seconds.
 
andy_fozzy said:
Turning it off for long periods apparantly stops the seals drying out. Leaving it on keeps the system 'healthy'........
Click to expand...

I think there's a disconnection between what you're thinking and what you're writing.
 
andy_fozzy said:
Leaving it on apparantly stops the seals drying out. Also leaving it on keeps the system 'healthy'........
Click to expand...

This is true

Sadly leaving it on permanently is also likely to put more wear on the compressor bearings.

I generally run it on a weekly basis and for demisting in winter.
 
Using the local garage price of 116.9 per litre, your £50 would have netted you 42.7716 litres of fuel which equates to 9.408 Gallons (UK).

Now, driving for 410 miles and assuming you used every drop of that £50 worth (and nothing more) then your fuel comsumption would have been miles/gallons = 410/9.408 = 43.57993 mpg.

THat's not too bad in all fairness, but that sort of maths is based on a fair few unknowns (price, miles and actuall amount of fuel used).

K
 
andy_fozzy said:
JESUS Rob :eek:
Where did you get a new compressor for £38???? :suspect:
Click to expand...

ebay...I did a double-take as well...only dropped the cash after I'd spoken to him on the phone. He was selling a shed-load of new Mk2 Mondeo parts which just happened to fit the Cougar...:thumbs:

I now have icy-cold lovliness at the push of a button - perfect now that it's no longer 37C here in Germany and back to the usual cold, rainy Summer weather we've come to expect...:suspect:
 
i fill my 1.8tdci and get around the same out of it without the aircon on, i just use air con sometimes, if its hot as it has been then its on but really needs a regas, its not as cold anymore and it smells a bit...
 
matty said:
i fill my 1.8tdci and get around the same out of it without the aircon on, i just use air con sometimes, if its hot as it has been then its on but really needs a regas, its not as cold anymore and it smells a bit...
Click to expand...

I usually switch it off about 5-10 minutes before the end of the journey and switch to full-blow to dry the pipes out a bit.
I've found that the condensation breeds all kinds of nasties otherwise...:gag:
 
Had turmoils with my focus air con too.

Apparently it is a known design fault that the compressor is ridiculously fragile and is sat right where stones get flicked up to. Mine apparently has a stone hole in it and the garage want £434 to fix it.

Tempted to do what Rob suggests and source parts elsewhere but worried how it may affect the warranty on rest of car?
 
You dont have to run the aircon all of the time - sounds like an urban myth to me.

Good quality a/c parts are designed to withstand a wide variety of usage patterns.

You should however use your a/c periodically (even if only for short periods) to stop what is effectively mould building up in the system due to condensation in the pipe. When this forms it causes an unpleasant damp smell from your a/c.

To measure fuel economy properly do the following:

Fill the car up with fuel until it is full. Reset your trip counter to zero. Drive until the car is low on fuel. Then refill the tank until it is full again. Then do the following calculation:

(Miles on trip counter / number of litres taken to refill the tank) * 4.54

Each time your refill the tank reset the trip counter to zero and start again.
 
ka$h said:
Using the local garage price of 116.9 per litre, your £50 would have netted you 42.7716 litres of fuel which equates to 9.408 Gallons (UK).

Now, driving for 410 miles and assuming you used every drop of that £50 worth (and nothing more) then your fuel comsumption would have been miles/gallons = 410/9.408 = 43.57993 mpg.

THat's not too bad in all fairness, but that sort of maths is based on a fair few unknowns (price, miles and actuall amount of fuel used).

K
Click to expand...

Nice one, thanks mate.

Just wanted a rough idea, like you said, a few unknown's such as did I use EVERY drop of the £50 fuel?
No not really!! I re-filled when the needle got almost to the bottom, so not all the £50 was used.........

And it wasn't 100% exactly 410 miles, of course.
But hey ho, got what I wanted which was a rough idea :thumbs:
 
Arkady said:
ebay...I did a double-take as well...only dropped the cash after I'd spoken to him on the phone. He was selling a shed-load of new Mk2 Mondeo parts which just happened to fit the Cougar...:thumbs:

I now have icy-cold lovliness at the push of a button - perfect now that it's no longer 37C here in Germany and back to the usual cold, rainy Summer weather we've come to expect...:suspect:
Click to expand...

Fair play to you mate, that's a cracking bargain :thumbs:
 
smoothedit said:
Had turmoils with my focus air con too.

Apparently it is a known design fault that the compressor is ridiculously fragile and is sat right where stones get flicked up to. Mine apparently has a stone hole in it and the garage want £434 to fix it.

Tempted to do what Rob suggests and source parts elsewhere but worried how it may affect the warranty on rest of car?
Click to expand...

This is indeed true.
It's right next to the drivers side wheel on my Focus, and is completely un-protected.
There's nothing to stop stones, water and god know's what else smashing in to it :bang:

The man who done mine says he could make a living on fitting new compressors to Focus's alone.
The reason he could do mine very reasonably was the fact that he buy's compressors in bulk, as he's know's he will use them!
 
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