My wife got me a used monster GT, the motor has about a gallon on it of byrons 45% fuel, there's 3 hobby shops within 50 miles and none of them have any, Will it hurt to use byrons 20%?
No, it is a myth that you can not change fuels. Run what you have with the proper heat range plug and retune the engine. I don't think Byron's even makes a 45% fuel for cars/trucks.
Gen2 20% is 12% oil--not a huge difference. I went straight from Blue Thunder (20% nitro, 20% oil) to Sidewinder 20% (12% oil) with zero ill effects and no re-tuning.
You can change fuels. It just takes some tuning, Especially going from 45% (?) down to 20%. I believe a medium plug will do fine, but someone may come by and correct me.