Hi All

Just wanted to share an experience with you, which might save you some money

When I changed to winter tires I immediately saw a decrease in fuel consumption, and when I changed back to summer tires again, I saw increased consumption – my wheels are 225/40-18. Some of it is due to the aerodynamics, which you can only deal with by changing width/rims… So since I use my car for everyday commute at the moment – and possibly for the next 3-4 months, I decided to look for an “eco alternative” (or as eco as it gets for a 2,0 TFSI). I stumbled upon the Pirelli Cinturato P7 as such an option for large low profile tires and decided to change from my worn out Michelin Pilot Sports to these new “magic” tires.

I have to admit that I am very pleased with their performance. Grip during rainy weather is obviously much better since the thread is deeper now, but dry weather grip sideways is also better (tested as top speed roundabouts with different diameters). In terms of acceleration and braking, they are very close in dry weather and I have been able to measure an average 0-100 (km/h) time difference of 0.15 in favor of the new tires – let’s call it a tie.

In terms of the fuel economy I previously drove 35km to work with an average of 13.2-13.5 km/l (31-31.7 mpg). Now, with the new Pirellis, I have an average of 14.5 – 14.8km/l (34.1-34.8mpg) everyday, same route, same speed – the same difference has shown during 5 full tanks.

The speed varies from 60-100km/h in those 35km, and it is the only sure measure I have for the fuel economy, but it still shows a clear difference. For me, personally, this means a saving of 1200DKR/£128 per year for the commute to work – so let’s hope the performance/economy continues throughout the life of the tire

Well, that's the same as I experienced, but I don't know about the difference between the new tires and the winter tires - time will tell :think:

Less unsprung weight on a smaller wheel and larger profile tyre - that will make a big difference to performance and economy. Try running 15" steelies with fatter tyres on a VRS that would normally have 18" s on it and see how much better it goes.

Also winter tyres should be a harder compound so less rolling resistance but at the same time colder weather brings about longer warm up times and greater volumetric efficiency so the car can take in a greater volume of air as it's more dense and thus inject more fuel. Means you shouldn't have to press the throttle as much to get the same levels of performance but I'm gearing my knowledge towards petrols and stoichiometric ratios to which diesels don't apply per se.

Less unsprung weight on a smaller wheel and larger profile tyre - that will make a big difference to performance and economy. Try running 15" steelies with fatter tyres on a VRS that would normally have 18" s on it and see how much better it goes.

Also winter tyres should be a harder compound so less rolling resistance but at the same time colder weather brings about longer warm up times and greater volumetric efficiency so the car can take in a greater volume of air as it's more dense and thus inject more fuel. Means you shouldn't have to press the throttle as much to get the same levels of performance but I'm gearing my knowledge towards petrols and stoichiometric ratios to which diesels don't apply per se.

You are right about all the theory behind what affects fuel consumption in the winter compared to summer...

With this topic, on the other hand, I just wanted to share my findings in regards to a summer tire vs. summer tire comparison - during summer

Have you factored in that you fitted your Winter tyres when the Ambient temperature was lower.

Not talking tyres here really..

thinking,

Stating in the morning and instead of 5 minutes untill your Thermostat opened at 88-90 degrees celcius it was maybe 10 minutes.

You started the car & defrosted,

& the engine ran and zero miles were covered.

Your Heater, rear screen, lights and radio were all on, heated mirrors as well maybe.

You were driving slower, like every one else, but not getting a good economy with your MPG.

If you went only 5-10 miles your Oil maybe only got to 50 degrees celcius.

Did you even get 25 mpg before stopping & the car cooling down again.

20 miles maybe before you were running oil at 88 degrees and getting up to your usual Summer MPG.

So more than just tyres or Air Conditioning to think about really.

george

Have you factored in that you fitted your Winter tyres when the Ambient temperature was lower.

Not talking tyres here really..

thinking,

Stating in the morning and instead of 5 minutes untill your Thermostat opened at 88-90 degrees celcius it was maybe 10 minutes.

You started the car & defrosted,

& the engine ran and zero miles were covered.

Your Heater, rear screen, lights and radio were all on, heated mirrors as well maybe.

You were driving slower, like every one else, but not getting a good economy with your MPG.

If you went only 5-10 miles your Oil maybe only got to 50 degrees celcius.

Did you even get 25 mpg before stopping & the car cooling down again.

20 miles maybe before you were running oil at 88 degrees and getting up to your usual Summer MPG.

So more than just tyres or Air Conditioning to think about really.

george

Please read my first post again

I changed tires this summer and got that improvement. Nothing to do with winter, snow, aircon and the like...

Changed tires in July - measured 1½ month prior to change and 1½ month after change. So if I am not mistaken I didn't drive through the winter while measuring. The temperature here has averaged between 18 and 25C mostly...

Yes i did read.

I did not see where you said when you said you changed to Winters and saw a decrease in Economy

& when you changed to Summer.

(my bad that i thought you were talking Winter & Summer seasons and not Summer only)

& sorry i was making a general reply and not really to your OP, sorry.

**I noticed you never mentioned Tyre Pressures in the original post,

or ambient or road temps only rainy or dry roads..**

Our UK temp seems to have been since last October till now, -10 to 32 degrees celcius.

Local to me was 4 degrees celcius the other night, so looks like its Winter tyre again soon,

just as well i have kept them on since last year.

Narrower tyres and slower speeds have nearly always given me better fuel economy over the years, regardless of the tread,

& adjusting tyre pressures to the temperature and tyre choice. Also driving style.

unless that was Narrow Mud Tyres that is.

http://ntda.co.uk/im...reLabelling.pdf

http://www.bbc.co.uk/news/uk-18663023

Soon we are all going to have Tyres & Economy, noise, rammed down our throats.

george

No problem

I just thought: "Well... Let's try those "green" tires" and they work

Narrower tires + slowing down = a definitive winner.

Less unsprung weight on a smaller wheel and larger profile tyre - that will make a big difference to performance and economy. Try running 15" steelies with fatter tyres on a VRS that would normally have 18" s on it and see how much better it goes.

Also winter tyres should be a harder compound so less rolling resistance but at the same time colder weather brings about longer warm up times and greater volumetric efficiency so the car can take in a greater volume of air as it's more dense and thus inject more fuel. Means you shouldn't have to press the throttle as much to get the same levels of performance but I'm gearing my knowledge towards petrols and stoichiometric ratios to which diesels don't apply per se.

Are you sure about that?? I thought they were significantly softer as the tread needs to move around to generate the grip, I also thought this is why they will wear out so quickly if you try and run them outside of winter as the warmer weather means they will just wear out as they're so soft?

Yeah you're right. God knows what was going through my head. Need coffee.... :-)