Hi

I've got a 1.2tsi 105, used to get 48-52mpg on my 14mile 'a' Road commute to work, I'm now getting 43-44mpg.

I did have winter tyres on, 15" steelies and a cone air filter.

Recently put standard 17" alloys back on for, dare I say summer and the mpg has dropped.

I have made sure tyres are at correct pressure and removed the cone filter and reconnected the OEM filter and still not back up to old mpg.

My driving style hasn't changed, temp has gone up a few degrees if anything.

Could the tyres make that much difference to efficiency as nothing else has changed?

Any ideas would be appreciated

Jon

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The latter figures are roughly what I've always got on standard 17" alloys, never used winters so haven't got any experience of them.

Was the rolling diameter of the winters the same as the 17 inchers, could've been messing with the calibration of the computer if they weren't.

As far as I'm aware the rolling diameter was the same, tyres aren't my thing really. I can put the sizes up and maybe a tyre guru....George.... May be able to tell me (that's not a dig)

If that's what your averaging Gaz then so be it. I'm going by the computer so you might be right about the difference. I wasn't sure if the mpg was worked out by the exertion/labour of the engine or if it took tyre rotation into account.

If that's the case I'm putting my filter back on, I miss the hearing the turbo spooling up!

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I'm sure the computer just divides the amount of fuel used by distance covered so if the diameters are different then the miles covered and the travelling speed would be different also.

Would be good to make the induction sound a bit sportier, maybe look into it at some point.

I'm sure the computer just divides the amount of fuel used by distance covered so if the diameters are different then the miles covered and the travelling speed would be different also.

Would be good to make the induction sound a bit sportier, maybe look into it at some point.

 

Hmmmm. Anything suitable for a derv induction wise? I really want to have a subtle sportiness to mine.

The universal cone on mine cost the princely sum of £15 so not Bank breaking. You get the sound of the turbo spooling, a slightly deeper engine Note and a definite 'tish' when you let off the gas, not as good as a BOV by any means.

I'm not sure what the engine bay looks like on the derv so couldn't say if my set up would work, there is a pic of it on another thread, looks a bit messy but I had just cobbled it together as a trial.

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This is the pic

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Edited 27 April, 201412 yr by jonro2009

What width of Tread is now on the ground compared to the winter tyres,

& What is the tyre pressures you are now running.?

 

Even with tyres that are 205/40 R 70 you can get a Brand that has your car doing 2-3 MPG less,

even when the are the same total diameter/rolling circumference.

 

Tyre have different Wear Rates, Traction, Economy & Noise ratings because they have different Compounds and treads.

 

http://kouki.co.uk/utilities/visual-tyre-size-calculator

 

No need for

'as far as i am aware the rolling diameter was the same'

 

Could you not have just compared physically the 2 different Wheels/Tyres side by side?

I don't have the winters with the car just now, they are being stored.

Like I said I'm not familiar with tyres and rolling diameters etc.

Using the website you linked George, here are the results....

Would this account for the different readings on the maxi dot since the tyre change?

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If the tyres were as shown by the numbers,

but sometimes when actually measured side by side the tyres will be less than the percentage difference.

 

As it is, if you are on Standard Filter & Standard tyre size, just see how the real MPG is Brimmed to Brimmed,

see if your mileage covered tallies with GPS.

 

I find i get better MPG with Winter Spec Petrol Oct - March when its not really a hard winter.

I did this Winter.

 

george

I'll do that cheers.

So it's a multitude of variables to take into account.

I'll keep an eye on things, I filled up the other day so will do a check at next fill up.

It's amount of miles covered divided by fuel used in gallons to get your true mpg, correct?

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4.456 litres to a gallon.  

near as damn it 9 litres 2 gallons.

 

40 litres near enough 9 gallons.

 

So if you brim it easy enough to zero the miles, brim it next time, and see how many litres used.

(no gallons show on petrol pumps. never have for a long time.)

Have always found I get better mpg on my winter wheels. In my case (on a diesel), around 5mpg, though as George suggests, there are other factors at play too.

Tyre choice makes a huge difference. Even on the standard 17s I've seen a drop of around 3mpg switching from continental to Pirelli.

I'm on continental now, my winters were nankang. Guess I will just put up with it then. Good to know what's going on though, if the didn't look so crap I'd leave the winters on....

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Bigger (overall diameter) wheel/tyre combinations mean you travel further but the car doesn't know; likewise smaller ones and the car travels less.  It is this figure that the car uses for the mpg calculation.

 

According to the trip computer, has your commute journey suddenly got shorter, per chance?

 

Also, wider tyres (205 vs 185) generally have a higher rolling resistance - and also the brand and type of tyre changes this too.  You could have a few percent difference there, add in a few more from the tyre size, and that could be a large amount of the difference you've seen..

Never had more than 43 average m.p.g. according to the trip computer out of my 1.2 TSI 105 Monte, running on Continental standard 17" wheels and tyres.

Bigger (overall diameter) wheel/tyre combinations mean you travel further but the car doesn't know; likewise smaller ones and the car travels less. It is this figure that the car uses for the mpg calculation.

According to the trip computer, has your commute journey suddenly got shorter, per chance?

Also, wider tyres (205 vs 185) generally have a higher rolling resistance - and also the brand and type of tyre changes this too. You could have a few percent difference there, add in a few more from the tyre size, and that could be a large amount of the difference you've seen..

Thanks

I haven't noticed a difference in distance but can't say I have checked. I'll look next time I drive to work. I'll also check the true mpg brim to brim.

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Is this too obvious?

Winter...air con off.

Now...on 

Today certainly,  Scorchio.!,  

 

Later this week freezio!

Is this too obvious?

Winter...air con off.

Now...on

You would expect the MPG to get better after the winter not worse though.

As far as air con is concerned, why would the use increase in April, he doesn't live in Tenerife or Cyprus, he lives in the far north of Scotland.

You would expect the MPG to get better after the winter not worse though.

As far as air con is concerned, why would the use increase in April, he doesn't live in Tenerife or Cyprus, he lives in the far north of Scotland.

It was just a casual suggestion,I've not done a detailed appraisal of local weather conditions.

The OP will know when he uses air con and when he doesn't,not you.

19 *oC this afternoon,   lovely,

Road Temperature 39 *oC

 

AC on,  MPG difference N/A,  Nothing, Ziltz.

I averaged 44mpg from my VRS this morning on my 22 mile trip to work. Best so far from the 743 miles she's done from new.

Phil.

I averaged 44mpg from my VRS this morning on my 22 mile trip to work. Best so far from the 743 miles she's done from new.

Phil.

I don't use the air con at the moment, it was only 11° here today. I rarely use it tbh unless it's roasting, so that's not often! Fair suggestion though XK140

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