LRR Tires. My Experience
 

I purchased a used 2016 Prius 2, not the eco, on Feb.11 2017. It has 18xxx miles on it. The tires were the Toyo Nanoenergy A29 P195/65R-15. In Feb of this year the tires were in need of replacement. I have put on a little over 63,000 miles in one year. I drive for Uber and Lyft. I put over 5,000 miles a month on the car.
I went online and found some tires on sale at NTB. Buy 3 get one free. Sumitomo HTR A/S P02. They are a 65,000 mile tire.
I noticed within a few miles that my MPG had dropped, it was at 48mpg according to the readout on the car. CRAP! After driving around delivering people I got it up to 52 mpg. Crap! again. Something is not right. I am always between 58 and 63 mpg. The next day I figured things would be better. NOPE! I could not get above 52.4 mpg. I knew it had to be the tires. Nothing else had changed. I called NTB and told them I would be returning the tires. Why? Because the are sucking my gas away.
After doing some searching via google I determined that the Toyo tires I had originally were LRR tires. Shopped around and found the best price at Tire Rack .com.
Had them installed at Firestone and returned the other tires to NTB. They gave me the money back for the tires and tax only.
Immediately my gas mileage went back up into the 58 to 63 mpg range.
LRR tires are worth the money.

So that's about a 13% reduction in fuel economy.

Things to consider:

New tires always get poor fuel economy until they wear in a little.
Measure the circumference of the new tire vs old. A larger circumference will under-report distance travelled and throw off speed and MPG estimates.

Certainly the non-LRR tires resulted in a reduction in MPG, but I find it difficult to believe 13% less. I would think different tires would account for only a 5% or less difference.

Factor in the fact that you'll have to replace the tires more frequently. That's a big cost that could offset fuel savings.

Redpoint5, you would be wrong in your assumption. I lived it. I know my car. The drop in mileage was very surprising to me. The fact that the mileage went back up to my "normal" proves that the tires sucked as far as mpg goes. Why do you think I will be replacing tires more frequently?

If you run the math, a worn out tire in that size will over report miles by 2% vs a brand new tire with full tread depth. I.E., it will appear the vehicle is getting better mileage than it actually is.

LRR vs non-LRR mpg will certainly show up on high mpg cars, but new tires WILL consume more energy than worn tires.

And finally, they're sumitomo, what did you expect?

*facepalm*

*double facepalm*

Correlation is not causation.

By the way, there should be no difference in distance reported between new and worn tires, even though the new tires have a slightly larger circumference.

Amazing, no?

Consider this: A tire on a car is not a perfect circle. The contact patch is flattened out, and there the tread shrinks; the grooves narrow as the lugs get squeezed together.

By and large the distance a wheel travels with each rotation is the same as the length of the steel belts in the tire. The distance between the belts and the tread surface has no influence; again, the contact patch is flat.

Actually, if anything it is the other way round.
As my tires wear I see a very gradual reduction in the reported distance of my commute on the odometer. The same route that was 35.6 km when the tires were new now takes just 35.4 km.
I bet the belts have been stretched ever so slightly.

Worn tires slightly underreport the mileage.

Supposedly it can take up to 4,000 to 5,000 miles to break in tires to get normal gas milage.
Worn tires get the best mileage.
Seeing a 13% different is a little bit of a surprise. I would have guessed up to 10% max.

Added this to the wiki.

A couple of points:

1) LRR is not an absolute term. It means "better fuel economy compared to other tires with the same traction and wear characteristics".

So it is quite possible to get worse fuel economy with a tire labeled LRR than one not so labeled.

2) For tires, there is a technological triangle involving treadwear, traction and rolling resistance. In order to get good values in one area, one or both of the others has to be sacrificed.

3) OEM tires almost always have really good fuel economy, but they do that by sacrificing traction and/or treadwear. That's why OE tires are considered poor quality - the goal was good F/E, not good wear.

The OE tire mention by the OP (Toyo Nanoenergy A29) has a UTQG rating of 300 A B. The treadwear rating is really low.

4) As tires wear, the RR decreases. So getting new tires should always result in a loss of F/E - all other things being equal.

5) There is no break in for RR in tires. The first few thousand miles have fairly rapid wear, so the F/E improves quickly as the tread is worn away, but RR continues to improve until it reaches its best numbers just before being worn out.