Over the years, I've changed tires on a lot of vehicles and have never really noticed any adverse MPG effects from it.


Back in August, I replaced all 4 tires on the my 2007 Fit Sport. Prior to the tire change I had logged about 14k miles and averaged about 33.5 mpg. Over 49 tanks of gas, I got below 31mpg twice and both were on big mountain trips with a full car and mountain bikes on the back. I was running 39psi in the front tires and 35psi in the rears.


After the tire swap, I've only gotten over 31mpg once and I'm averaging around 30 mpg. I've played with tire air pressures anywhere from 32psi to 44psi and I can't seem to find anything that makes much of a difference. Had the alignment checked and a couple things were out but not by much. If anything, the alignment actually hurt my fuel economy. My daily commute is about 55 miles round trip and it's there are a few lights but it's mostly smooth flowing 45-70mph roads.


Any opinions on this? I've never seen a 10% decrease in fuel economy just by switching tires. This is about 3 times what a low rolling resistance tire advertises over a normal tire and my last tires weren't even low rolling resistance tires.

 

I've read that new tires will give you a mileage hit at first until they wear in enough to smooth everything out. But that's a pretty big drop.

What tires did you have and what did you switch to?

 

I wish I could remember exactly what the original tires were but they were cheapo's and rather no namers. The new tires are cheapo's as well and are GT Radial Champiro VP1.


The one thing I have noticed about these tires is that the fronts always look different. One day they look like they need air and the next they look fine. They're currently at 42psi so I find it kinda odd that they can look bulged at times with that kind of pressure. Maybe they have really soft side walls that are more noticeable with temperature changes. I'm in GA so the daily temperature swings aren't that severe.

 

CMFs berforming badly and/or erratically. That makes sense.

 

Well at the rate I currently put miles on this car, I guess the consolation is that these tires won't be on the car more than 2-3 years.

 

there are 2 things at work. are the new tires heavier? if they you will see a definite drop in mpg. simple physics the heavier the tire the harder it si to rotate. if your new tire is greater in diameter there's another part of bigger diameter & heavier tires are harder to rotate.
second thing at work could be the gas; an increase in ethanol contamination will also lower mpg.
the only thing that can help but not much is greater tire pressure. try 43 psig.
ps we've seen guys opting for really wide tires like 225/50x15 section getting mpg's in LOWER 20's.

 

^^ Along with what mahout said (tire weight, width, and fuel energy/quality) there's how much friction the tire has with the road.
LRR tires offer lower friction aka poorer traction. They are generally narrower than traditional or performance tires (again width)
so they are aerodynamically more efficient. The FT-86 twins ran a damn Prius tire, which was a contributing factor in their 34 MPG HWY
rating. There are also variations in overall diameter within a given tire size, effectively changing your final drive ratio
(195/55/R15's aren't all exactly 23.4" tall).

 

Ignoring power conversion, power transmission losses in the vehicle, and driving habits. The next two losses are wind (air) resistance and then rolling resistance of the tires.

Rolling resistance of the tire has mostly to do with construction materials used and tread design. I run 2 snow tires on my Colorado in in the winter. I immediately see about a 15 % mpg loss when I switch to them. That is only switching two of the 4 tires. That mpg immediately returns when I switch back to my normal LRR tires.

For your next set of tires I suggest that you look at Yokohama Acid Ascend if they make them in your tire size. We had them on a 2009 Fit Sport and saw about a 4% improvement in mpg over the OEM junk Dunlops. They were a good all season tire in the snow with good dry pavement traction.

 

I keep scrupulous MPG records on our CR-V as I use it for business.

Over the first 20K miles, MPG gradually improved, and we attributed it to engine break-in. WRONG.


It was the tires getting old. New tires knocked the MPG down 4 - 6%.


This has repeated every set of tires (always replaced in fours).


Tire Rack even has a tech article on this.

http://www.tirerack.com/tires/tirete...sp?techid=177&

 

the oem tires are LRR. what tire sizes are you using? 195/55?