Ok so here is may story a little background for me in a nutshell I have been a mechanic for 10 years a former Honda tech and currently a reserve officer and Hyundai tech.
So doing the part time police officer gig on the weekends I travel a lot so I decided to buy a 07 HCH.

After I got it I noticed it wasn’t getting very good mileage. I did some looking on the Internet and found the 33mpg horror stores on a few hybrid forums and I figured I just made a 16k dollar mistake. I had the battery dump issue and still do and the low SOC The terrible update had been performed before I bought it.
So to make a long story short I called Honda customer relations 2 times with no real answer and the first guy acted like he could care less about my car that is supposed to get 40+ in town that was actually getting 29 to 32 mpg in town.
The IMA battery stayed at 5 to 3 bars ALL the time never ever ever ever saw 6 bars much less 7 or 8 so I figured the IMA battery was toast or the nasty update was screwing it. 4 trips to the Honda dealer I worked at once upon a time with no real results other than the “we checked it no problems found “ routine I decided to do a little experiment.

I set out a 14.5-mile track though town that included some stop and go traffic and hills with some straight stretches too.

Here were the results
2010 new off the lot HCH 45.3 mpg
My 2007 HCH 32.6 MPG

After driving my HCH for 1000 + miles I was use to the way it drove I noticed a large difference in the way the 2 cars drove the 2011 felt like it just rolled better.
Going up hills it would charge the IMA id never see that in mine so my next experiment was to ask the dealer if they would swap wheels with me, they thought I was nuts but they did it for me.

The results were astonishing!
First run with my car I did the 14.5-mile track at 44.8 mpg with a lot of lunchtime traffic at 12:00 noon I could not believe the difference! The car just rolled better, after that I waited till 6 pm did it again with a whole lot less traffic 49.2-mpg holy crap! The IMA charge stays at 6+ bars now and rarely do I see 5 WOW!
Mainly because the car rolls better it charges the battery now. Still have the battery dump but it recharges fast.

I never thought in a million years tires would make such a difference the Yokohamas the dealer put on prior to selling the car were brand new but apparently the rolling resistance they have the poor HCH thought it went back and forth to work up hill both ways.
I now have Kumho eco Solus HM KR22 tires aired to 40 psi.
Tirerack.com labeled them as a Low Rolling Resistance tire so I got them after putting them on I went to their website and found that they are a 100k mile tire but not a true LLR tire that irritated me highly as well. I should have got the ecowing but still the mileage im getting is great compared to what it was.
Hope this info helps



Log showing mpg after tire change IS stands for Interstate H for Highway C for City



low mpg Yokohamas



New tires



Best I did

 

Leave it to the dealer to put non-LRR tires on a hybrid! Trying to save some money no doubt. My experience and from everything I've read tire type and pressure are the two most important factors in why the Civic hybrid attains anywhere near 40 mpg or better. I have the OE dunlops that need to be replaced. Two of them leak slightly, and I can always tell when they are low by my mileage. If your tires' sidewall psi rating is higher than the 40 you're running at go to max and see another jump in MPG. I heard of some running their tires at 50 psi. I run mine at the max of 44 psi

 

yea they are rated at 44 i figured 40 would be safe

 

Great experiment! Explains my poor in-town mileage(~35) tho' I still get 55mpg on highway in my 2003 HCH. I'm going to pump up the pressure and see what happens. Oh, I've had the "battery" issue many times with the symptom being not starting even tho' it reads 12.5volts cold and 14-15volts hot which is sposed to be correct.See ya later!

 

I Read this last week, and decided to test it, My car had new tires when i bought it but i didnt think about weither they were lrr or not, well they arent, which explains my 22 to 27 mpg range (besides a bad battery) My tires are rated for 51 psi, so I Took them to 46, and Immediately noticed a difference in how the car felt rolling, felt easier, and my mpg went from 22 to 27 ish city to 37 to 39 city and 42 hwy with teh ac on (its normally 100+ here), and with the ac off, 44 city and 49, Thank you for showing us this as I never would have realized not havining lrr tires was a big issue with my car

 

Sounds more like a tire pressure issue than a lrr one. I have non-lrr tires and still get 41.5 mpg--with a bad battery. I like the low noise and smooth ride that the Kumho KR21s give at 44 psi.