Well, after the October snow storm where it took me 6 hours and alot of sliding around to get home, I decided to get all season tires with good snow traction. I picked up the Hankook Optimo H727 and had them installed at Walmart on 11/21/2011. Right away, my MPG dropped significantly. Before the tire change, I was getting from 47.4-53.6 MPG with an average of 50.7 MPG. After the tire change I got from 43.9-46.6 with an average of 45 MPG after 8 fill ups. So I took it for my 15k service and they rotated the tires. Immediately, my MPG skyrocketed with the first tank at 49.3 MPG. The next one went to 51.3 MPG and the near empty tank i'm on now is at 49.5 MPG. When I took it for service, I told them that my MPG dropped and they checked it thoroughly. They found no problems, except a dirty air filter . It was barely dirty after I checked it myself, but I replaced it anyways with a cheap one. I asked them if the tires could make a difference and they said no. I've had no change in driving habits. Also, I even used 40/38 PSI after I got the new tires installed. After the tire rotation, I used 35/33 and I still got much higher MPG. Did Walmart install the tires improperly? Any ideas?
First of all, there is no such thing as a good all-season snow tire. All-season tires are a compromise for a summer tire & a winter tire. For where you live you should have a good winter tire during the colder, snowy months where the temps are below 45F. As far as the MPG, the tire rotation itself would not have any effect on mpg. Tire pressure may have have changed over time or just be a coincidence. There are so many variables when it comes to mileage, just keep that in mind. I'm sure the tires are just fine but new tires will always have a mileage hit compared to worn out tires. Do a search & you will find many threads on the subject.
In my area there is no 'all-season' snow tire that really works. We run a set of studded winter tires, and a set of cheap summer tires. I find it likely that when they first put on your 'all-season's their pressure was low. Then later when the tires were rotated, they bumped up the pressure.
Tire rotation shouldn't cause significant and lasting mpg change. There could be a temporary drop in mpg due to old wear patterns and now the tires will wear according to their new position. This should be a slight drop and nothing like what you are reporting and in the opposite direction no less. I agree that an all-season tire does not cut it in temps below about 40-45 degrees. Tire pliability is much reduced so braking distance is greatly increased. The best option is to run a dedicated set of winter tires if temperatures are below 45 degrees most of the winter. Another option is to run a winter tire that does ok in the summer for your year-round tire choice. Something like the Nokian WR series tires. They are designed for lower temperatures but can handle warmer temperatures whereas all-season tires are warm weather tires that can sometimes do ok in cold temps but are not designed for them. Remember it's not just your safety you have to be concerned with when choosing and mainlining tires on your car.
As with F8L's comment, I run winter tires all year on both my vehicles. I run Nokian WRg2 on the Prius, and big nasty snow tires on the Jeep. The WRg2 tires tolerate our short summers pretty well without a big mileage hit, and the Jeep never goes fast enough to matter, plus how would I notice a mileage hit with a Jeep. If Michigan would allow studded tires, I would probably switch between summer and winter tires. Since we can't do that lawfully, I stick with winter tires. Tom
Based upon the dates and your location, I would think that the weather has had a lot to do with this. It has been much warmer than normal these past two weeks in the Northeast, and our mileage has gone up quite a bit on the past two tanks as well with not change in the vehicle or driving habits. I's say to chalk it up to the weather.
There is no such thing as a good all-season tire in snow in any area. I hate studs though as they decrease traction on dry & wet roads. The new breed of studless winter tires perform beautifully in all winter conditions without the road noise of studs, plus they don't tear up the roads.
I'm surprised that you don't use a good LRR tire for the 6 months of weather that the snow tires aren't needed. Your mileage would be much better & your winter tires would last longer too.
I experience the same thing you did here regularly. I believe that every time you get a rotation (or get new tires) there is a break-in period where the tires wear themselves perfectly to the road/angle of the wheel (i.e. the tires become more "friction-less"). Until that happens (at about 3-5k miles) you experience lower mileage (10-15% lower) It always (for me) creeps back up to it's maximum by around 4.5k miles. I know plenty of people disagree with me, but it is predictable, and happens every time. For example, I just got a new prius, and initially (because of the new tires) it only got around 48 mpg. by the first 5k miles, it crept up to 55 mpg. Then, at 5k miles, (upon the first tire roatation), it plumented down to 48.9. Now, it will creep back up to 55 mpg.
