Selecting New tires 2018 Prius Two

While I consider 52mpg at 70mph to be normal, I am used to driving on winter tires inflated to 50psi, which actually gives better mpg than stock tires. Having mpg drop 20% without a major change in speed or conditions, is not something I've ever experienced in any Prius, and it's 24 years since I got my first one.

Personally, I'd check what the "max load at max psi" pressure on the tires might be (hopefully at least 44psi, preferably 50 or 51) and pump up all 4 corners to that value, to see what mpg you get.

Every Prius has marginal tires specified, where you really, really, really don't want to be driving with any tire at 30psi, that is asking for a blowout due to overloading. Check out the load capacity of tires versus pressure, on tirepressure.org

I recommend going up several numbers in load index, by buying XL tires. Note that XL tires don't usually reach their full rated capacity until 42psi, unlike standard SL tires which reach theirs at any pressure from 36psi to their max. Personally I go slightly up in size also, from 195/65R15 to 205/65R15 because again it adds load capacity, plus I've never met a Prius that couldn't use more ground clearance. It also got me from load index 89 up to 99, so the tires are expecting the weight of a minivan, and last longer with only the weight of a Prius (which is heavier that you'd think) on them.

 

Pirelli are quite, nice gripping tires, but they wear out fast - especially when your doing a lot of highway driving. This was on an Acura Interga, no telling what kind of mileage hit your going to take. The gasser Interga, no mileage drop
I got these a month ago:BLU-TRAC PC | Armstrong Tires in an XL UTOG 700 traction & temperature rating A. They're quite but I did notice a mpg hit. Hopefully it'll settle down when they break-in. Running @ 40 psi, may go up to 42 psi.
I popped holes in two of my OEMs with UTOG 340.

 

When are you putting air in your tires. From your description it seems you are adding air to hot tires. Or am I mistaken? If I’m not mistaken then I doubt you have a problem (the odds of all 4 tires having air leaks of the same amount at the same time has to be astronomical!).

 

Hankook has a wide variety of tires. Electric car tires is another phrase I see. I may look at the Kinergy PT as it is supposed to be made in USA when I need tires. My used Prime came with Kinergy 4s2 or something, original owner must have changed them. I am getting very good mpg, above the fifties. But I take advantage of the e v button especially in traffic on the highway. Electric only efficiency also hangs in around 5.2 miles/ kwh, mostly suburb type activity. Range about 34 miles pretty consistently.
I don’t drive fast, or aggressively accelerate.

 

Original poster should note that the individual advocating for higher weight capacity tires is a Prime owner, and that an empty 4th generation Prime is about 300 pounds / 140 kilos heavier than a conventional Prius Hybrid. I would be interested in the opinion of other conventional hybrid owners whether that 'upgrade' can be justified. (Although running tires well above Toyota's recommended pressures puts additional stress on tires and vehicle mechanics, so perhaps a tire upgrade might be justifiable. Also, the advocate does not address how heavily their vehicle is typically loaded.)

Note that an 'empty' fuel tank would only offset a Prime weight increase by about 60 pounds / 27 kilos.

I agree that the original poster might need to be more systematic about when (and perhaps how) they check and inflate their tires. Given the observed performance changes said to be accompanying the reduction in fuel economy perhaps there are other mechanical or drive train issues at play.

 

Your logic is sound, but I don't care about a few mpg since my current avg. is 118 mpg on my current commute. I do add EV consumption to my fuel log monthly from my electric bill. Since I don't have a spare tire, that's more of a concern. Had two flats on two different tires on the OEM shoes. I replace early, about 1/32 before hitting the warning bars, because of a very good sale on a complete tire package.
Your correct, to each their own - It just isn't safe standing on the side of the road, shoving a highway plug into a tire and reinflating. Neither is changing a tire off a busy highway - that reasoning factored into the heavier tire set.
FWIW - I've caught more flats in this car than my entire 50 years of driving.... Hopefully these new shoes will rectify that...