Phil you shouldn't have any problems. I'm highly certain the mogas I use has the same or similar detergents detergents.
I have always thought that 100LL is just awful fuel. The lead contaminates your oil, forms sludge deposits particularly in the crank, and prevents us from being able to use more modern synthetic oils. Lead spark plug fouling and huge lead deposits on the faces of pistons are common.
With my hodges fuel volatility tester I've only found a marginal difference in safe vapor pressures. In the real world, as others have posted here, you can get vapor lock with 100LL although its much less likely. The main root cause of this is the nature of how our yesteryear fuel systems are designed. Since the pumps draw fuel from the tanks, they work just like the tester does in causing vapor to form...by sucking on the fuel line. If you pump gas from the tanks, under pressure, this will never be a problem. This is why the fuel system in my rocket uses pumps at the tanks which negates the need for a fuel selector.
In your case, as in the case with my flying RV, it doesn't have this type of pump setup, so the best insurance on warmer days to prevent vapor lock is to run the boost pump all the time. I have climbed many times on 95 degree OAT days to altitude with the boost pump on, and have had no problems. But I found this out inadvertently one day when I forgot to turn the boost pump on, and was climbing out and started to get a rough running engine. Turning on the boost pump instantly took care of the rough running.
Another area when I do have had an occasional problem is with a quick turnaround on a hot day. Since fuel is sitting in the carburetor bowl boiling, it will be difficult to start and once it does start, the engine will want to quit taxiing out. The easy cure for this is to open the oil door after landing to mitigate heat soaking the engine compartment. Seems to work for me.
The other time I have had vapor issues is when taxiing out on a hot day, and have been held by a controller or traffic with an extended period of idling. Running the power up to 1200-1500 rpm will mitigate this problem by forcing that nice fan up front to cool things.
As far as octane goes, everyone seems to say only use premium fuel. I have not found regular 87 octane to be detrimental in any way.
On our airpark we have a 500gal tank I fill up from. On a trip to NC last November I had difficulties starting and thats the only time in almost ten years I've had that problem, and I attribute it to bad gas. Our tank was running low and the fuel in it was a couple of months old.
You certainly can mix the fuels as I have to all the time on trips where mogas is unavailable.
