I had a thread on this.
BMW 328i in NC
I changed the oil and topped off with BP Prem (may have up to 10% ethanol)
Been driving it every 10 days for 20 minutes for 2 months.
Still have a 1/2 tank with 4 oz of STA-BIL.
Thinking of the ethanol that may or may not be in the tank. 10 months till he gets back.
Do I top off with non ethanol?
Hurry and burn off more and then top off?
Keep going as I have been then top off?
The "modern fuel going bad" is one of the biggest internet myths around. While valid for carbureted engines, it has no merit with today's fuel injection systems which are pretty well sealed so the fuel isn't prone to oxidation. I've had half a dozen cars in storage with gas over 4 years old that run just fine with the old gas when I put them back on the road. One even with 8 year old gas. No reason to drive it every 10 days. Just fill it up with gas so there is less chance of water condensation, inflate the tires to 50 psi and park it with a battery maintainer. Then you can take the tag off and cancel insurance to save some money as well.