It's difficult to compare rolling resistance between tire brands because there is no rolling resistance testing standard in the US. We have to rely on independent/manufacturer testing. I sifted through a lot of this data and based my tire selection largely on conclusions I drew from these tests.
Low rolling resistance tires make a difference. One thing these tests rarely mention is how driving style impacts the results you will experience. A car driven "normally" will get slightly better mileage running low rolling resistance tires...but maybe not enough to notice unless you're closely tracking your fuel mileage.
On the other hand, a car driven conservatively will extract the most benefit from a LRR tire. When you're doing simple hyper-miler tricks like coasting up to red lights, etc...a LRR tire will provide a noticeable bump in fuel mileage. After 50,000 miles of my own testing, I feel pretty confident saying that my Mirage would not consistently net 50+ mpg if I suddenly changed to a non-LRR tire.
LRR tires are certainly not a silver bullet for good fuel economy. Your driving situations and habits play the biggest roles. But...if you have mastered your "ECO" driving habits and are looking for the next step in increasing your fuel economy, LRR tires are easily the next thing I would tell someone to do. Just do your research and get LRR tires with acceptable driving characteristics AND long tread life (and don't buy until you get a mfr rebate!).
On a related note...how cool would it be to test rolling resistance with a tricycle fitted with car tires?
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View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)