Since purchasing my Prius in December of 2006, I’ve had 3 sets of tires. The stock Bridgestone Turanza EL400′s, the Bridgestone Potenza G019 Grid’s, and now the Bridgestone Ecopia EP422′s. Yes, it seems I have a thing for Bridgestone, but really, it’s just because there’s a Bridgestone/Firestone here in town that originally did an online pricematch for the Potenza’s, and then when they failed early (cupping), they gave me a large discount on the Ecopia’s.
Since I’ve had the Ecopia’s for over 10k miles now, I thought I’d circle back around, and do an analysis of my mileage with each, and see if there is really any solid comparison. Subjectively, before running any numbers, I feel like the Turanza’s gave better mileage than the Potenza’s, and the Ecopia’s have given me better mileage than both.
Without further ado, here’s the data.
| Num Tanks | Total Gals | Total Cost | Avg Calc MPG | Avg MFD MPG | |
|---|---|---|---|---|---|
| Turanza | 29 | 227.326 | $680.06 | 45.35 | 45.99 |
| Potenza | 29 | 238.49 | $622.21 | 42.14 | 43.21 |
| Ecopia | 27 | 212.062 | $800.75 | 47.96 | 48.70 |
A couple things jump out here, at least to me.
- Gas prices have gone up quite a bit since I’ve gotten these tires.
- My guess was correct, and those Potenza’s were murder on my mileage.
The first item is kind of shocking, and I guess corroborated by a Wall St. Journal article just published. Interestingly, I also followed the trend, and my consumption of fuel went down (the national average was 3.6%, where my average was over 10%. In the sample here, cost per tank for the Turanza’s was 23.45 on average, for the Potenza’s, $21.46, and for the Ecopia’s, $29.66! Even with the increased mileage, that means the cost per mile for the three sets of tires, averaged over 10k miles, was $0.07/mile, $0.06/mile, and $0.08/mile respectively. That’s a pretty significant price increase over previous years.
Anyway, cost aside, with the second item, the mileage decrease from the stock tires to the Potenza’s was approximately 2.8MPG or about a 6% decrease. From the Potenza’s to the Ecopia’s was about a 5.5MPG increase, or 12.7%. And between the stock Turanza’s to the Ecopia’s, was a 2.7MPG or about 5.9% increase. Interestingly, that means the difference between the Potenza’s to the Turanza’s to the Ecopia’s were all about the same, and explains why Toyota moved to true Low Rolling Resistance (LRR) tires instead of the Turanza’s. That may also make up for the MPG difference between the Gen2 Prius, and the Gen3… use of LRR tires.
So there we have it. Low Rolling Resistance tires are not a joke, and Toyota obviously put some effort into finding a good option when they first released the Prius and LRR tires weren’t available. I just wish LRR tires in my tire size when I went to replace the stock ones, and I didn’t suffer for a couple years with the Potenza’s.
