tire size vs efficiency question

[nailers]

Hi, I have a 2001 Volvo V70XC with AWD so I'm not getting great mpg no matter what I'm afraid. It's time for new tires so I was reading threads here about efficiency. I saw a lot from Tire Geek refering to Barry's Tech that wider profile and taller tires decrease rolling resistance but increase drag and there's some discussion about the speed at which drag is more critical. The OEM size is 215/65R16 98H which if I don't drop down to T rated leaves 2 choices. I've been told that the load factor 98 is important so I want to stay at that, which rules out a lot of "eco" tires. I'm also limited to what's in stock at a local vendor (long story) which is: Michelin Defender GreenX 215/65R16 98T 22lbs, Michelin Latitude Tour HP 215/65R16 98H, Pirelli Scorpion STR 215/65R16 98V 24lbs, Michelin Primacy MXV4 235/60R16 100H 28lb, Sumitomo Tour Plus LST 215/65R16 98T 24.5lbs. Any fuel efficiency advice? From what I read maybe the 235/60 is the way to go. I only get 20-28mpg anyhow, with those I'd have a really good tire. Thanks.

[shovel]

It's worth noting that at the same pressure, your contact patch is roughly the same size regardless of tire width or diameter. There's some fun science about scrub meridians and all that good stuff but I feel that's mostly relevant in racing or high performance driving.

For anecdotal happy fun times, I recently changed from 245/65-17" to 225/75-16" tires on my 02 WJ and immediately felt the difference in coasting, and returned unexpectedly good average consumption on last weekend's ~800mi road trip. I'm going to stick with narrower tires, personally.

[ConnClark]

Changing tire width (even going thinner) can have bad effects on aero. Too wide and they increase the frontal area. Too thin and your wheel wells become gaping holes.