I was getting 32 mpg with my OEM steelies. Decided I didn't like hubcaps and got a good deal on OEM alloys. Now I'm getting 30mpg. Is it the weight difference? Difference in circumference (reading fewer miles traveled on the odo)? Change in driving habits since we've had the vehicle for 2 months? Other?

 

not sure about the weight of the steelies, but the OEM alloy wheels are 17.4 lbs each. that's a heavy 15" wheel

 

Probably your driving style I have 17" wheels on my car that weight 21lbs each and I found out this past weekend that I can get 40+ mpg on the highway so I doubt it is the added weight.

 

there's so many variables in MPG. it's not even funny. changing the overall diameter of your wheels will change your speed, which will change your miles traveled. also, you NEVER fill the tank to the exact same level. so that throws off your readings.

 

I can't say that I have had ever had that low of mileage around the city. I'll vote change in driving habits.

 

I agree, change in conditions. I try my hardest to be consistent with my driving but you can't control things around you especially people

 

Yeah, that's why I went through a couple of tanks before raising the issue. The before and the after have been very consistent across multiple fill-ups. Could still be the excitement of having cooler looking wheels tho'.

 

lol. dude, do you have a scangauge? if you care about mileage, you'd LOVE a scangauge

 

I'm pretty sure the OD on the two are different
Look it up on a tire site
P175/65-14 and
P195/55-15 sport I think this a larger around and will change the speedo/odometer

 

I"ve been following the scangauge threads closely for just that reason but wanted to get through my mp3 player adventure before springing for another gadget. I've been looking at the laptop adaptor/software that can be had for around $80. I think it gives you more parameters and the display is better although is less handy for full time use due to size.

 

According to this site U.S And Metric Tire Size Information Calculator the difference is about 2%. Not enough to account for a 6% change in mpg.

 

I checked the trip odo against my gps and the odo is reading around 8% under. It was on the money before the swap so that explains the mysterious decrease in mpg. I'm not sure how a 2% change in circumference could result in an 8% decrease in mpg though. Is the GPS a good odo calibrator? Any way to calibrate the Fit odo? Thanks RG

 

Pull one off and weight it.
I have a Sport and can weight a Sport wheel.
Maybe a user can weigh a steel wheel with hup cap.

Trust in GOD but everyone else bring the data.

 

Thanks, but after using the GPS to check the odo, I'm convinced it isn't the weight. Can the odo/speedo be calibrated on these cars?

 

"Neg-rep'd by Claymore" Crew

What's that about????

 

I copied it from another member's sig - I got neg rep'd by claymore and now consider it a badge of pride so I put it in my sig too. Based on your exchange with claymore in the EGR thread, you'll be part of the crew soon.

 

Probably but the weight fartherest from the hub is really the cause. If you on wider tires or larger diameter tires the added weight at the outside diameter is the reason for lost mpg. Of course if your diameter changed are yopu correcting odometer reading to get correct mpg?

 

yah, the drag from the tires might be the issue here. also temperature.

the tires are different sizes between the 14's and 15's even though they
are similar in circumference and width.

also wat psi are you running on the 15" alloy's? alway helps to run 2psi
more than wat's on the doorsill. most times manufacturers put the psi
for comfort, not so much for performance.

 

I wasn't correcting for the odo change because I wasn't sure how off it was. Can I reasonably use the GPS to calibrate the odo? Based on my initial look, I'm off by 8%.

 

I'm running @ 35 psi.