Octane also matters depending on the type of engine. Turbo/Supercharged engines will likely benefit with higher octane (and usually there's a recommendation for "Premium Fuel" in the owner's manual). More O2 in the charged air volume, more likelihood of preignition under compression.
Naturally aspirated engines, like the 5.7l Hemi, don't usually have a problem with an overabundance of O2 in the intake cycle and can usually get by with lower octane levels.
When I make trips across country, I will buy the equivalent *grade* fuel for what I buy at home. The formulations are typically suited to the local area.
Premium at octanes varying from 89 to 93 for the twin turbo Mercedes GL 450. Regular from 85 to 89 (if I remember correctly) for the naturally aspirated Hyundai Azera GDI V6. Once I get my RAM in the next few weeks, it'll probably be 87 octane unless I notice any issues. I may even try 85 to see how the engine performs.
This is from the manual for the 5.7l Hemi;
5.7L Engine
Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine. This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended for optimum performance and fuel economy.
While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see your dealer immediately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty.
"Plus" or mid-grade is 87 octane here.