We made the switch to 215/55R17s on the GF's CT to make the harsh ride a little softer. It's not life changing but it certainly helps to round out those sharp hits. It doesn't help that she has an F Sport. I chose Continentals as well because typically they have a softer side wall. But going 215/55s give almost another inch of sidewall. Of course the speedo is off but not by much, around 70mph indicated, you're going 72mph according to Waze. Not sure on mileage yet but even before she only manages 38mpg because she drives crazy. Yet I somehow manage 45-50 without really trying.

 

I also went to 215/55/17 a year agp and have been able to keep up 42+ all around, more on when in city driving 45+, mine is a base model. I recently switched off this week from Toyota 0W20 oil to M1 0W20 AFE and I know there are some chemistry differences, but would like to see what a 10K run does, also went with a Wix Filter. Every oil change I also run a bottle of Redline Fuel System Cleaner. Apart from that run a K&N in both the engine and in the cabin (pricey indeed for both).

 

The closer you can get to the Prius 15" wheels, the better. At low speeds (below 50) there's little to no reason a CT200h can't rival the Prius's fuel economy. At higher speed, the higher .cD of the CT would cause an MPG hit. there's weight but the difference isn't all that much.

Of course the CT would look horrible with the Prius wheels or any other 15" wheel. but damn does it help the fuel economy.

 

Also running 215/55s. 50s don't make a noticable difference, but you do notice it at 55. You may rub on the inside of the fender on full lock turning.

Lex, I use M1's XP oil, with a Wix XP filter myself. I run 15k oil changes, but was able to go as high as 28k without serious issues.

You shouldn't need the fuel cleaner if you use top tier gas. That's all I use and my engine looks new inside.

Also, M1's XP oil is now rated for 20k miles instead of 15k, and they added a high mileage variant so now you don't have to choose between the two. $27 for a 5q jug at Walmart.

 

Sometimes, my driver's side front will rub on significant bumps, but not much. I may go M1 XP next time around as I actually was down to the AFE and that when I bit and it was around $22 on Amazon as I had some credits from gift certificates to use and got that and the Wix. The 55s definitely are kinder to the ride, even the few passengers that saw the before and after a few years ago noticed it.

 

If it were my car, I'd run 15s or 16s all day long to get a cushier sidewall. But she didn't want to buy wheels as well. She was already due for tires.

As far as engine oil and filters, I just run OEM everything and change the oil every 10k miles.

 

I feel the same way about the wheels. If cost wasn't an issue, I would have done that.

 

My base CT200h use 215/45/17 tires. If switch over the 215/50/17 would increase sidewall height by +0.42", tire height by +0.84", tire circum by +2.63" and rev/mile by -26.93. Anyone know if 50 series will rub during a turn-on-turn steering? In theory, is it going to improve or decrease MPG? Thank you and look forward to your comments.

 

When I switched to 50 series, I didn't encounter rubbing. I did at 55, though.

 

Thank you so much for your reply!! Hopefully, MPG will not be affected with going with 50 series.

 

I went with a 225/45/17, and found its a good alternative to the tiny OE tires.