Does Winter Fuel Lower MPG?

[oldsoul]

Ok, so I'm probably weird, stupid or missing something here. I'm not denying the science of MPGs and fuel with this. However...
Here in northern MN, my experience has been that THE BIGGEST factor in lower winter MPGs are tires, tire size specificity. Period. I run 16" factory wheels from a Passat and slightly over sized Continentals in the summer. During the winter I have 15" VW wheels (forget what they were off of) with significantly undersized tires (came off a Honda Fit, $100 for a barely used full set is hard to pass up). Summer tires put my speedo dead on, winter tires put it about 4%off. Last fall my car sat from late August(full tank of summer fuel) until late October when I put snow tires on. went from 43MPG down to 36MPG. Every year is a similar story. winter tires on, MPGs drop. summer tires go on, MPGs shoot right back up.

Now, I know my situation is fairly unique. However, I am also a heavy truck driver. We see almost no difference from summer fuel to winter fuel there either. Therefore, in my experience at least, the whole BTU argument seems a bit overstated. Longer warmup times would also make sense, if it actually played out as significant. I'm on the highway(65ish) within 3-4 minutes of startup year round, I'm up to temp within a 3 mile range regardless of ambient temp (-40 to 90). I am absolutely convinced that tire size will effect fuel consumption more than anything else, other than dramatic weight changes(ie dropping 50% or doubling your weight). To further demonstrate my point, we have five Peterbuilt trucks. Same engines, same transmissions, same drive axles, same tires. Three have 11x24.5 inch tires, two have 11x22.5 inch tires. That's about a 2 inch difference in height(I know the math looks wrong, tire sizing is weird). The trucks with the taller tires get around 3-5 percent BETTER fuel economy, despite being several years older.

My advise, if you want better fuel economy, get taller tires.

 

[PradoTDI]

Another thing I'll add, snow tires will significantly increase rolling resistance over summer tires, too.

Driving conditions could have an effect, too, my commute to work is only about 10 miles, all at speeds under 50mph. In the winter my coolant temp never reaches the middle of the gauge on my way to and from work.

 

[pompa dooz]

Ok, so I'm probably weird, stupid or missing something here. I'm not denying the science of MPGs and fuel with this. However...
Here in northern MN, my experience has been that THE BIGGEST factor in lower winter MPGs are tires, tire size specificity. Period. I run 16" factory wheels from a Passat and slightly over sized Continentals in the summer. During the winter I have 15" VW wheels (forget what they were off of) with significantly undersized tires (came off a Honda Fit, $100 for a barely used full set is hard to pass up). Summer tires put my speedo dead on, winter tires put it about 4%off. Last fall my car sat from late August(full tank of summer fuel) until late October when I put snow tires on. went from 43MPG down to 36MPG. Every year is a similar story. winter tires on, MPGs drop. summer tires go on, MPGs shoot right back up.

Now, I know my situation is fairly unique. However, I am also a heavy truck driver. We see almost no difference from summer fuel to winter fuel there either. Therefore, in my experience at least, the whole BTU argument seems a bit overstated. Longer warmup times would also make sense, if it actually played out as significant. I'm on the highway(65ish) within 3-4 minutes of startup year round, I'm up to temp within a 3 mile range regardless of ambient temp (-40 to 90). I am absolutely convinced that tire size will effect fuel consumption more than anything else, other than dramatic weight changes(ie dropping 50% or doubling your weight). To further demonstrate my point, we have five Peterbuilt trucks. Same engines, same transmissions, same drive axles, same tires. Three have 11x24.5 inch tires, two have 11x22.5 inch tires. That's about a 2 inch difference in height(I know the math looks wrong, tire sizing is weird). The trucks with the taller tires get around 3-5 percent BETTER fuel economy, despite being several years older.

My advise, if you want better fuel economy, get taller tires.

I'll go out on a thin branch and state for the record (though I'll deny everything in court) that myriad factors contribute to varying degrees to fuel consumption. You'll use the least amount of fuel by simply not starting the engine but also go zero distance unless you park on a hill. Even walking to the liquor store uses a copious amount of energy.

Lets face it, the universe is an evil bustard.

 

[kjclow]

Ok, so I'm probably weird, stupid or missing something here. I'm not denying the science of MPGs and fuel with this. However...
Here in northern MN, my experience has been that THE BIGGEST factor in lower winter MPGs are tires, tire size specificity. Period. I run 16" factory wheels from a Passat and slightly over sized Continentals in the summer. During the winter I have 15" VW wheels (forget what they were off of) with significantly undersized tires (came off a Honda Fit, $100 for a barely used full set is hard to pass up). Summer tires put my speedo dead on, winter tires put it about 4%off. Last fall my car sat from late August(full tank of summer fuel) until late October when I put snow tires on. went from 43MPG down to 36MPG. Every year is a similar story. winter tires on, MPGs drop. summer tires go on, MPGs shoot right back up.

Now, I know my situation is fairly unique. However, I am also a heavy truck driver. We see almost no difference from summer fuel to winter fuel there either. Therefore, in my experience at least, the whole BTU argument seems a bit overstated. Longer warmup times would also make sense, if it actually played out as significant. I'm on the highway(65ish) within 3-4 minutes of startup year round, I'm up to temp within a 3 mile range regardless of ambient temp (-40 to 90). I am absolutely convinced that tire size will effect fuel consumption more than anything else, other than dramatic weight changes(ie dropping 50% or doubling your weight). To further demonstrate my point, we have five Peterbuilt trucks. Same engines, same transmissions, same drive axles, same tires. Three have 11x24.5 inch tires, two have 11x22.5 inch tires. That's about a 2 inch difference in height(I know the math looks wrong, tire sizing is weird). The trucks with the taller tires get around 3-5 percent BETTER fuel economy, despite being several years older.

My advise, if you want better fuel economy, get taller tires.

Have you measured the odometer by gps with each set of tires to see if you're readings could be due to one tire giving greater distance than the other?

 

[oldsoul]

Have you measured the odometer by gps with each set of tires to see if you're readings could be due to one tire giving greater distance than the other?

It was actually using a known distance. However, even if I had used the odometer, the winter tires would have shown a longer distance, being smaller.