Tires and MPG?

The changing of the seasons and the subsequent tire/wheel swap has paid an unexpected dividend.

My MPG (according to the OBC) has gone from 23.2 to 27.8 since the changing of the tires.

There are some other qualifying factors.

1. Roof rack is generally on with the summer tires far more than the winter package.
Based on my own observations, the rack seems to subtract 1.5-2 MPG.

2. Temperatures are lower. A/C is only used for occasional defrosting and now and again
to exercise the system.

Surprisingly, average speed remains relatively constant, around 45mph.

Summer Package

Michelin Pilot Super Sport (go flat) 225/40 18" front 255/35 18" rear on the ever
popular 193M BMW wheel.

Winter package

225/40 18" Dunlop Wintersport 3D (RFT) all 4 corners on Sparco Pista wheels.

Has anyone else noticed a change in mileage between summer and winter setups?

jummo

Jummo,

Maybe the difference between summer & winter gas? That change in mpg is surprising to me.

Mine never varies more than 1-2 mpg unless on an extended road trip. g/l

More likely it has to do with a possible shift between winter and summer petrol formulations, and/or difference in fuel quality from tank-to-tank. Rolling resistance is a factor in tires but the difference is not that big, only a few tenths of a l/100km.

Originally Posted by jummo

The changing of the seasons and the subsequent tire/wheel swap has paid an unexpected dividend.

My MPG (according to the OBC) has gone from 23.2 to 27.8 since the changing of the tires.

There are some other qualifying factors.

1. Roof rack is generally on with the summer tires far more than the winter package.
Based on my own observations, the rack seems to subtract 1.5-2 MPG.

2. Temperatures are lower. A/C is only used for occasional defrosting and now and again
to exercise the system.

Surprisingly, average speed remains relatively constant, around 45mph.

Summer Package

Michelin Pilot Super Sport (go flat) 225/40 18" front 255/35 18" rear on the ever
popular 193M BMW wheel.

Winter package

225/40 18" Dunlop Wintersport 3D (RFT) all 4 corners on Sparco Pista wheels.

Has anyone else noticed a change in mileage between summer and winter setups?

jummo

Sorry, jummo...your switch to winter tires has resulted in exactly the opposite expectation for winter tires that are less fuel efficient than non-winter tires. Winter tires are horrible for rolling resistance...NO tire manufacturer in their right mind makes any claims for winter tire fuel efficiency. There are OTHER reasons for your DRAMATIC improvement in fuel efficiency...it's certainly NOT your fuel INEFFICIENT winter tires!

Originally Posted by pointandgo

Sorry, jummo...your switch to winter tires has resulted in exactly the opposite expectation for winter tires that are less fuel efficient than non-winter tires. Winter tires are horrible for rolling resistance...NO tire manufacturer in their right mind makes any claims for winter tire fuel efficiency. There are OTHER reasons for your DRAMATIC improvement in fuel efficiency...it's certainly NOT your fuel INEFFICIENT winter tires!

I'm not claiming that winter tires are more efficient, nor did I say the manufacturer said they were.

I merely noted that my fuel consumption has improved by almost 20%. This coincided with the switch from summer to winter mode for my car.

I find it curious, not that I am complaining, mind you.

It would seem to me that there are likely other factors. Colder temps? Seasonal gas blends?

I don't know, that's why I asked the question. I also noticed a similar decrease last May when making the switch to summer mode.

It never ceases to amaze me at the incredible knowledge of proper winter driving equipment
possessed by people who live in places where it doesn't actually snow.

It seems like such a waste, when so many people around here seem utterly clueless when the roads are bad.

Please note that I refrained from excessive use of capitol letters in anticipation of a potential
shortage.

With all resources, conservation is a good thing.

I am jummo, and I approved this message.

jummo

Hey Jummo, how was that trip to France? See any flamingos?

Originally Posted by GarySL

Hey Jummo, how was that trip to France? See any flamingos?

France was incredible, but we didn't see any flamingos! We toured several ski factories and each day featured a major vin et fromage session. And then a 3 hour dinner.

When the business part was done, we headed to Chateau Neuf Du Pape, down the Rhone Valley,
across the coast to Italy, where we spent a few days in the Cinque Terra.
Wow!

Back to the topic, we've had 17" of snow here at Casa jummo the last 2 days. The snow tires are earning their keep, along with the snowblower, roof rake etc.

Keep it coming and Go Broncos!

jummo

I have posted this before, but I have consistently seen better fuel economy with winter tires versus summer tires. This was true on my Subaru Legacy GT, my Infiniti G35X and now with my current 335. All cars had larger diameter summer tires (not that it should matter). I am 95% sure my area (Vermont) uses the same fuel summer or winter.

Some of this is probably due to the fact that I drive slower on winter tires but still. On this car the summer tires are staggered and winters are not. I just changed to winter tires 2 weeks ago. I made my same trip to NY and I saw 29 to 30mpg. On summer tires I get 27 to 28 mpg. If history repeats I will consistently see close to 30mpg until summer tires go on. I think it's also due to wheel weight and the previously mentioned AC usage. Just my two cents though.

Originally Posted by mossman35

I have posted this before, but I have consistently seen better fuel economy with winter tires versus summer tires. This was true on my Subaru Legacy GT, my Infiniti G35X and now with my current 335. All cars had larger diameter summer tires (not that it should matter). I am 95% sure my area (Vermont) uses the same fuel summer or winter.

Some of this is probably due to the fact that I drive slower on winter tires but still. On this car the summer tires are staggered and winters are not. I just changed to winter tires 2 weeks ago. I made my same trip to NY and I saw 29 to 30mpg. On summer tires I get 27 to 28 mpg. If history repeats I will consistently see close to 30mpg until summer tires go on. I think it's also due to wheel weight and the previously mentioned AC usage. Just my two cents though.

It's elementary my dear Watson. "Softer" compounds (high performance tires, snow tires) generate more heat...otherwise called "hysteresis loss." This results in poor fuel economy. Rubber chemistry and the laws of thermodynamics all rolled into one!

Snow tire rubber compounds are heavily "extended" with oils to keep them flexible in low temperatures. Terrible for "normal" temperatures! That's why they normally wear much quicker than "non-winter" tires. The heavy "siping" or "slits" in the tread detract from their fuel efficiency also. You may notice that "super fuel efficient green" tires now being offered on the market for hybrid cars have nearly "sipe-less" tread designs.

The compounding of new "green" tires contains "silica" or other ingredients to reduce "hysteresis," NOT the softening oils found in snow tires.

Originally Posted by pointandgo

It's elementary my dear Watson. "Softer" compounds (high performance tires, snow tires) generate more heat...otherwise called "hysteresis loss." This results in poor fuel economy. Rubber chemistry and the laws of thermodynamics all rolled into one!

Snow tire rubber compounds are heavily "extended" with oils to keep them flexible in low temperatures. Terrible for "normal" temperatures! That's why they normally wear much quicker than "non-winter" tires. The heavy "siping" or "slits" in the tread detract from their fuel efficiency also. You may notice that "super fuel efficient green" tires now being offered on the market for hybrid cars have nearly "sipe-less" tread designs.

The compounding of new "green" tires contains "silica" or other ingredients to reduce "hysteresis," NOT the softening oils found in snow tires.

I understand what you are saying but other things are playing into this. As a matter of fact I am currently half way through my 5 hour drive back to vt. Temp is in high 40's low 50's. I am getting 28.6 mpg on extreme winter contact. I never see that high on summer ps2's. I have been doing roughly same speed. The winters are narrower. Wheel weight is less. Something other than tire compound has a bigger influence. Like I said my last 3 cars showed same thing. All this assumes car calculation is equal.

Pictures worth 1000 words. Haha.

Another fresh pic. Time to finish my drive. I never tire of driving this car. Be back later. :-)

After several more hours my trip is complete.

I know comments ended here a while back, but I am averaging ~19 MPG with my winter Blizzaks. This seems oddly horrendous. I have a '10 335xi.

Is this normal?

Originally Posted by agbasher

I know comments ended here a while back, but I am averaging ~19 MPG with my winter Blizzaks. This seems oddly horrendous. I have a '10 335xi.

Is this normal?

Yes. I think some of the reasons for this are covered (above).

I'm not surprised. The roof rack affect aerodynamics therefore the increased wind resistence causes more fuel to burn. Also, the winter set has 4 equal rims, the summer has larger rear rims, therefore the summer wheels are heavier. Another reason for the inferior mileage. It appears there is not much you can do about it since you drive the same average speed.