I do have to agree with you on the issue of running 87 in a run-of-the-mill Mazda. If memory serves me correctly, this will be our 5th Mazda vehicle. A Mazda 5 GT, then a Mazda Tribute and now going on to our 3rd CX-5. Always run them all on 87 or whatever was the standard "cheap" gas at the time. Never have had any issues.Absolutely false. I have no idea why a sales rep would try to dissuade you from spending more money.
Some would argue that the turbo isn't worth the extra money based on the HP/TQ increases or because of the added potential risk of one more thing that could break. These are valid arguments depending on the person buying - but you are leasing. You would be under the factory powertrain warranty during the lease, so in the event that the engine/turbo does have issues, you wouldn't be the one paying for the repairs.
Mainly though, the statement that running 87 would lead to premature fouling issues and turbo issues is not true at all. These engines were designed to run primarily on 87 and we have many users on this board who have been running 87 for years with no issues.
Having said that, I'm not sure personally whether I would want to repeat that on a turbo'd vehicle, even if it's based on the bread/butter Mazda 2.5L. No doubt with modern electronics and computers to dial back on the valve and ignition timing, etc. the motors can handle the cheaper fuel but if you want to run a turbo, I'd say be prepared to shell out the extra cash for the good gas, otherwise, what's the point. I know that I'm not about to start paying the premium for 93; even if it was available in our area. The highest gas I've run across lately is only 91.
For me, there's no doubt that this will be the last "gas only" vehicle we purchase/lease as I'm fed up of being "hosed" at the pumps with artificially high gas prices. If Mazda doesn't have a proper plug-in Hybrid next time around; I'll switch to another brand of vehicle.