My oil consumption ranges 1500-2000 miles per quart depending. After a fresh oil change, it can go 2K before the 1 quart low warning comes on. Then thereafter, it will go to 1500 but depending how I drive overall can yield back up to 2K. This is all on the stock thermostat.
When it is time for my next oil change, I will re document the new oil consumption to accurately answer the question as if it truly improves the consumption while utilizing the 90C thermo.
Even if it stays the same......this is still a great upgrade if you want to experience more consistent performance when your engine is at operating temps. That I can accurately tell you that there is a difference in overall operation of this engine. It's more "Alive" if you will.
Especially if you live in hotter climate, this is it.
I remember going to Sears one day and my Fiance wanted to wait in the car. It was around 85 degrees outside with AC set at 73. Around 10 mins I come back and saw my oil temp is at 250 degrees straight up. I'm like WOW, she runs hot.....
Now, I did a similar scenario but I was waiting in the car for about 15mins and outside was around 90-91 degrees ( IIRC, it was hot as balls.) The oil temp needle never reach past over the number "2" on the gauge. Check the coolant and it rest at 100-101C. After a minute of driving, it goes back down to 96-97C. And it runs well too.