[BearClaw0001]

Hello,
I have an 09 Forester XT. I have determined that I at least want to put 91 octane in my forester, but I am looking to save some money. Has anyone tried octane booster with mid-grade or regular fuel for their Subaru Turbo? Theoretically can I mix half and half of 89 (mid-grade) and 93(premium) to make 91?

Thanks

 

[Mr.AC]

Well lets do the math. How much is 93 per gallon? How much is 89 per gallon?
About how many gallons does it take to fill the tank?

Without knowing how much per gallon you think you are saving. It really turns out like $3-4 more.

Here in California our 89 is 3.37/gallon. 91 is 3.57/gallon. My tank to fill up is 14 gallons.
For 89 I pay $47.18
For 91 I pay $49.98
For $2.80 more I get 91.

Now how much is a bottle of octane booster? Are you really saving money and extra effort by getting cheap gas and buying a octane booster?

 

[Kean]

.....you also need to realize that when some of these octane boosters claim to raise octane in "points", they actually mean ".x". In other words, a product claiming to raise octane by 2-5 points likely means ".2 - .5" in actuality. .....making a tank of 89 only 89.2 - 89.5.

If you're really hell bent on trying to blend grades to get a tank of 91 octane, use one of the many calculators available online. Here's one I found in a quick search:

Octane Mixture Calculator

I haven't done something like this in years but that was when I was trying to create a 93 blend here in CA where we only have 91. There was a 76 station that used to carry 100 octane unleaded at one of their pumps.

I think you'll realize the savings just aren't there and if there is, it's not much at all to warrant the trouble.