Old Lar

The "super" hypermilers on cleanmpg do have some bizaare ideas on getting exceptional mpgs. Many techniques I don't believe in ie turing off the car at traffic lights and driving at the minimum posted limits on the interstates. Neither actions are safe IMHO. Many of the claims being made I find unbelievable. But it takes all kinds. I'm still averaging a tad over 30 mpg on mixed driving which is more than the HHR is rated. My prvious car, a Buick Regal GS w a 3800SC engine, I also got better mileage than the car was rated. Using cruise control on the highway and not kicking in the SC too frequently was the reason. But the car did like premium gas or at least mid grade to get it running well. After seven years and over 100K miles it was time for a change.

ZTony8

Fitting taller tires only gives an artificial increase in m.p.g.It just changes the speedo and odo readings,not the true velocity with which the car moves along the road.It's still gonna move at 88 feet per second at 60 m.p.h.,for example,no matter what the gauge reads.

The Curly 1

Taller tires do help. My tires are taller than stock and gives me a 4% speedo error. That is my car actually travels 4% farther and gets 4% better mileage than indicated.
The RPM is a little lower with the taller tires and the mileage little better. I have also verified the speedo with my GPS. Even with out adding the 4% speedo error it is better. That is because it makes the overall gear ratio just a little taller. Making the car get better mileage and accererate a little slower and have a few MPH higher top speed.
Note my performance numbers do not have the 4% added it should. If you add that the mileage is a little better.
Also my tires are too wide for real mileage (IMHO) and I think if I had choose a narrower tire of the same height it would be several MPG better. Traction is not an issue so I could have made a better choice.

IgottaWoody

How much of a change are you seeing in milage with the tires?

masterchief1112

just something to think about. you may want to get your speedo adjusted for the taller tires. 4% can really add up, it would mean you are at your 100000 warranty 4% faster. someone who i trust in the auto business also told me that they can put something on your title for not getting it fixed in a timely manner and consiter it tampering with the odometer

The Curly 1

I picked up 2.5 to 3 MPG actual mileage. One thing is I lowered it at the same time so I can definatively say it helps but difficult to say exactly how much. Tires and lowering were a verifiable 2.5+ increase and I suspect most all of it is the tires.

I also know I could have made a much better tire choice and it would give much better results. My tires are really too wide and that hurts it.

I have a drag race car and by just putting the "Skinny's" up front the car was faster and noticeably easier to push around in the staging lanes.

Saving weight will help you save gas on acceleration but less rolling resistance will help you at all speeds. Taller gear or tire helps your mileage more so at highway speeds than stop and go but it helps.

I know the taller tire will give you 2.5 to 3 MPG better and I really am very confident that a more narrow tire would increase that a few more MPG.

Keep in mind if you use your car for drag racing a shorter tire (gear rato) would be better. But if mileage is your goal taller is better with in reason.

ebacherville

80% of hypermiling is driving technique.. put the instant mpg on you dash and treat it like a battle between you and the car, the slower you drive typically will be best.. I was able to jump in the HHR on the drive home from the dealer and plop down a 33mpg average over 30 miles.. thats 3 better than EPA, now on e85 im averageing about 28mpg so far.. better than EPA again..

One HUGE one in new automatic cars is rollig to to a stop, when your let off the acccelertor the injectors shut down and you use no fuel, so anticipate slow downs or stops and try to roll as long and far as possable. just by rolling a mile or so every time you come down from high speeds can increase averages allot and it also saved your break pads too.

dkenthoward

I know that slowing down makes a difference....today on the freeway....traveled at 60 mph and averaged 38.8 mpg....at 80 I get about 30 mpg and sometimes lower...

Crooz

Huh??? Using the speedo to calculate miles covered would give a decrease in mpg if taller tires were installed. ie. You would have went say 107 miles when in fact your speedo would show 100.
Also, Velocity has nothing to do with mpg.

ZTony8

Velocity DOES affect m.p.g. -mainly due to increased air drag and increased engine r.p.m. as the speed rises.You get better mileage at 45 than you do at 70,for example(everything else being the same).If you don't,something is very wrong.
Yeah,I goofed about the tire size deal.OOPS.