You're not going to save 10% on wheel treatments. There's no getting around the fact that you're going to have to slow down.
The good news is that saving 10% doesn't require going all that much slower. My guess would be something like 4 MPH slower. It's the "mod" that improves all drag producing parts of the vehicle.
Here's the various mods for consideration. None except the extreme ones are going to get you 10%.
https://ecomodder.com/forum/fuel-eco...ifications.php