Hey guys -

As the title states, I got gas tonight and the gas attendant must have not heard me and since it was late, I didn't notice that he pumped (2) gallons of 87 octane; before anyone says anything, I live in NJ and by law the attendants pump the gas.

Well I stopped the attendant at (2) and got another 7-8 gallons of 93 on top of what was already in the tank. I have a tune on the car by IveyTune which is fairly conservative (322whp/313tq).

Should I go out of my way for an octane booster or should I just try to lay off the boost and once I hit 3/4 of a tank, get it filled with 93 octane again? Thanks.

 

octane boosters are a waste, just take it easy and then fill it up with 93.

 

Thanks. I have an evo x by the way. Accidently posted in here.

 

I wouldnt get on the car till you refill with 93

 

Yeah NJ sucks.. No idea how many times this had happened to me. I've tried octane boosters but they've had no worthwhile effect to me. Just take it easy for a little bit, never hurts to be too safe.

 

Agreed. Something similar happened to me, though when I saw the little bottle of octane booster at autozone for $15, it seemed like a ripoff, especially when 100 octane is $10/gallon. So I just went with the 100 octane at a nearby station.

 

I have a sunoco station about 10-15 minutes from me that apparently has race gas which I assume is 98 octane or higher.

Would it be worth getting to like 3/4 tank and getting a few gallons of race gas?

 

Yeah, more or less. I did the math calculations and knew how much 100 octane I needed to get the tank to even out, so I kind of just drove around city streets taking it easy until I knew I could probably fit the proper amount.

 

With that mix you're at 92.1 octane. (2*87+ 93*8)/10 So, car will be completely fine even if you get on it.

 

What is the capacity in gallons of a X fuel tank anyway? Is it just 10 gallons?

 

OK I checked and the fuel capacity of an Evo X gas tank is 14.5 U.S. gallons. So, did the OP fill the tank at the gas station. If he filled he would have 2 gallons of Regular and 12.5 gallons of Super in the tank, right? If he didn't fill the tank then we wouldn't know how many gallons of Super were already in the tank before the attendant pumped in the 2 gallons of regular and the 8 gallons of super would we? Unless he actually filled the tank, trying to figure out the overall octane of his Super/ Regular blend would be impossible.

 

But, mithrandir7533 is right in that OP added 10 gallons of 92.1 blended octane to however many gallons of 93 octane gas was already in his Evo's fuel tank.

 

I had a quarter tank of 93 prior to the fill up. I got about 2 gallons of 87 and then 7 or so gallons of 93.

So that means I should have about 12.5 gallons of 93 since the tank holds 14.5 I believe.

 

So:

12.5(93)=1162.50

2.0(87)=174

1162.50+174=1336.50

Finally: 1336.50÷14.5=92.17

The octane of that accidentally blended tankful of gasoline works out to be 92.17(R+M/2). The difference between 93 vs 92.17 given a conservative pump gas tune, is not worth your losing any sleep over.

 

So, mithrandir7533, was spot on with his calculation