LT vs LTZ MPG

[Watchdoc]

browing the fuelly Sonic's I noticed the LTZ's were getting roughly 3mpg worse than the LT models with the 1.4 turbo.

Keep in mind, this is a very small sample of cars so take my observation with a grain of salt.

I'm guessing the LTZ weighs slightly more since it comes with a spare tire and heavier wheels with wider tires.

If this observation holds true and the Sonic's mpg is so sensitive to tires and unsprung weight, then Cruze Eco wheels and Ecotopia tires might make a dramatic difference.

 

[RichieRocket]

browing the fuelly Sonic's I noticed the LTZ's were getting roughly 3mpg worse than the LT models with the 1.4 turbo.

Keep in mind, this is a very small sample of cars so take my observation with a grain of salt.

I'm guessing the LTZ weighs slightly more since it comes with a spare tire and heavier wheels with wider tires.

If this observation holds true and the Sonic's mpg is so sensitive to tires and unsprung weight, then Cruze Eco wheels and Ecotopia tires might make a dramatic difference.

Watchdoc, maybe people with LTZ's just drive them harder

The 17" wheels will add drag, for aero drag: 205 vs. 195 width and those 17" 5-spoke wheels chopping thru the air, less chop on the 15" 5-spoke.

Not sure how rolling resistance would compare, depends on tire compound and construction, not sure about width.

You are right though, the sample size is too small...

 

[theenico]

I'm guessing the LTZ weighs slightly more since it comes with a spare tire and heavier wheels with wider tires.

My LT came with a spare tire.

 

[Eric Smit]

My LT came with a spare tire.

+1.


-Eric Smit

 

[wingman]

I have no spare on my LT. But when I went from the stock 15's to 17's on a 225/45 I lost that 3 mpg.

 

[theenico]

I wonder if the spare tire to inflator kit was a running/interim change.

 

[Sonic Boomer]

Hmm, The larger diameter should result in less rolling friction, but I guess the wider tire (increasing the contact patch size) increases it (along with the larger air resistance). Still, I wouldn't expect to see ~10% loss!
I wonder what the change in gearing from the larger diameter wheels does.

Wingman, are you compensating for your odometer readings? I know this is not an accurate assumption, but if you were actually going from 15 diameter to 17 diameter, you would travel about 12% farther for each revolution of the wheel after rubber and lower profiles on the 17's, I would SWAG it at around 5% or so.

 

[Ferdie]

You're right


I have the LTZ and the dad of my girl the LT

he gets 6.1L on 100km and i get 6.5L on 100km

the manuel said its the same but that's not true

 

[RichieRocket]

Hmm, The larger diameter should result in less rolling friction, but I guess the wider tire (increasing the contact patch size) increases it (along with the larger air resistance). Still, I wouldn't expect to see ~10% loss!
I wonder what the change in gearing from the larger diameter wheels does.

Wingman, are you compensating for your odometer readings? I know this is not an accurate assumption, but if you were actually going from 15 diameter to 17 diameter, you would travel about 12% farther for each revolution of the wheel after rubber and lower profiles on the 17's, I would SWAG it at around 5% or so.

Sonic Boomer, all three of the Sonic's stock OEM tire's rolling diameter are close (within 0.2"):
From Tire Rack:
195/65-15 24.9" dia
205/55-16 24.9" dia
205/50-17 25.1" dia <1% difference

The 15" versus 17" is for the rim, not tire...

For wingman's 225/45-17, not sure what brand, looking at Tire Rack, that diameter of performance tires in that size are in the 24.9" to 25.1" range. So no need to adjust the speedo/odo.

The aero resistance comes from 1) the air having to go around a wider tire and 2) the larger spokes in the open rim chop thru more air
That's why I was thinking of making smooth hub caps out of cheap Aluminum pizza pans for use on long highway trips

 

[SteveSonic]

You're right on the money, RichieRocket, about the tire diameters.

Tire rolling resistance is caused by several factors with most internal to the tire's construction. CleanMPG found the RR of the stock tires on the LTZ to be horrible. That along could account for the mpg differences seen btwn the models.

I'm going to be on Fuelly very soon to test my own claim about averaging over 40 mpg in my 1.4T HB.