Only Sunoco carries 91 octane in my area. Most stations have 87, 89, and 93. The 2015 owner's manual says minimum 89 and recommended 91. For fuel quality it says:

"To avoid harmful engine deposits, it is highly recommended to purchase gasoline from Top Tier retailers."

Citgo has the lowest price near me and is Top Tier, so I use that. There's no 91, so I alternate between 89 and 93, usually going with 93.

 

LOL. Ok, you will now have had one... my old aircooled VW's always have a problem with carburetor icing when the preheat tube is clogged.

 

I read that my 08 Base Mini R56 needed premium, so I've only put 93 in it. However, tonight as I was filling up, I noticed that there was an option I had never seen

before. As you can see in the picture, there's an option for 90 100% Non Ethanol Gasoline. Is this better?

 

Check your car's owners manual but I believe 90 octane is not supported.

If it is then you can try 90 ethanol free and see how the engine does.

While the lack of ethanol is a good thing the 90 octane is a bad thing.

 

I thought to look on NAM, but didn't think to Google for some reason. I just found this on 90 Ethanol Free octane.

REC-90 is an ethanol-free, 90 octane unleaded gasoline blend designed for use in recreational/marine engines which can be damaged by the ethanol found in other gasoline blends. It is also usable in some aviation engines [1] and automotive engines, though it has not been thoroughly tested for cars and trucks.

 

Ethanol provides some Octane boost. Remember what "Octane rating" is...it's a measurement of resistance to pre-ignition. Octane it NOT a measure of Quality. The Additive Package is more related to Quality than Octane...and, you don't know what Additive Package is in either fuel, unless it is posted, and you can compare, and you know what you're comparing it to. Keep in mind that MORE Detergent doesn't make a fuel "better", since detergent is not fuel. Detergent can boost Octane (depending upon the Detergent used), but, more is not necessarily better.

So, if your engine requires 93 to avoid pre-ignition, 93 with ethanol would gemerally be better than 90 without ethanol.

 

If you don't mind faffing about at the pump, octane ratings blend pretty linearly, so if you know you're going to put in 12 gallons:
6 gal 93 + 6 gal 89 = 12 gal 91
8 gal 93 + 4 gal 87 = 12 gal 91

Sometimes that even saves money! I've only done it a couple of times as it's not usually worth the effort, and requires two transactions. I just put in the lowest grade that is equal to or better than recommended.

 

Ha, I've never thought of it that way. I'm pretty sure we're not allowed to mix octanes at the pump here in Alabama...at least not in a single transaction.

 

That is entirely too much work when I can just fill the Mini's 12ish gallon gas tank with 93 for a small difference in price.

I filled my truck's gas tank yesterday from about 1/8th full. $83 for 87. And you guys are in here talking about cutting gasoline to save $1.50 per tank for a car that gets an easy 25mpg.

 

Not here. I’m all about putting the best in. It’s easier to pay more at the pump than it is to pay the mechanic. I was just wondering what “the best” was.

 

Im going to try a 2 gal e85/ 10 gal 93 mix next fill-up, have been reading a lot about this mix lately on forum.

 

Anything that is above the manufacturer's minimum octane rating (or your car's tune rating if applicable) and not going to damage emissions equipment.

This forum over complicates the simplest things.