Michelin Primacy MXM4 tires have worse gas milage than the MXV4*

[JEDI]

*mxv4 tread at 3/32"
mxm4 at full tread (10/32")


mxv4 (3/32" tread) was giving me 33mpg the past 6 fillups. (300miles/week)
these new mxm4s have given me ~30.5 mpg for each of the 2 full fillups i've had w/it.

both were inflated to 40psi.
no other changes to the car.

the mxm4's so called 'Green-X' tech that claims better gas milage.
A+ to the marketing guy!

so why does less tread give better mpg?!

 

[Ferzerp]

What is your tire diameter? As they wear, your indicated speed is faster than it really is (not by 10% though). Sure the effect is small, but it is present.

That would account for something like a ~2% difference if your total diameter was 20" for example.

edit: also, you really need many more datapoints than 2 tanks worth of fuel since driving style has a huge impact on mpg.

 

[JEDI]

What is your tire diameter? As they wear, your indicated speed is faster than it really is (not by 10% though). Sure the effect is small, but it is present.

That would account for something like a ~2% difference if your total diameter was 20" for example.

edit: also, you really need many more datapoints than 2 tanks worth of fuel since driving style has a huge impact on mpg.

16" tires.

same driving: work + groceries + gym + friends
nothing out of the usual

 

[Ferzerp]

16" total diameter, or 16" wheels?

 

[JEDI]

16" total diameter, or 16" wheels?

whats the diff?

tire size:
205/55/r16

 

[NutBucket]

I think he was asking if the new tires are the same size as the old ones.

My $0.02 is that tires play a huge role in fuel economy and I'm not all surprised you noticed a difference. That being said, I would not expect the "improved" version to have increased rolling resistance over the previous version. You may want to talk to your tire guy and it may be worthwhile to call Michelin and ask them.

 

[phucheneh]

He's asking about rolling diameter. Which can and does differ betweeb tires of the same size and brand. Look at the 'specs' page on Tirerack.

 

[Howard]

Yes, I too have them and the LRR part seems to be grossly exaggerated at best.

 

[Kelvrick]

My MXV4's say green-x on them too...

 

[BassBomb]

If you are in winter prone areas the gas may have switched over to winter version, some loss there

Also the old tires are less grippy so they'll have better mileage strangely. The new tires are a lot safer and more grip.

And as people have said, the change in diameter just from the wear can result in some mileage differences (assuming you kept the same actual tire size).

 

[Ferzerp]

the change in diameter just from the wear can result in some mileage differences

Well, apparent mileage, but little effect on actual mileage. As your tires wear, your speedometer reports a higher speed and your odometer clocks more miles, so you calculate higher mileage.

 

[thomsbrain]

Taller tread blocks = more tread squirm = more lost energy. Plus changing weather conditions/gas blends can make big differences. Colder weather means longer warmups and worse gas mileage, even if you don't need the A/C anymore.

 

[rommelrommel]

40 psi sounds high?

 

[fr]

I would get the same drop in MPG due to winter blend in CA. I switched from Fusion HRI to MXM4 and noticed no change in MPG from the tires.