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First, I am new here but I am familiar with the search and have referred to the combined gas thread http://www.8thcivic.com/forums/showthread.php?t=2358. So mods please do not close this thread, I believe it is a slightly different question than what has been posted in there, and is nearly impossible to go through 73 pages of posts about what mileage people are getting to get any answers.

My car was getting close to E so I stopped at a Shell off the highway. Seemed expensive there so I wasn't going to fill up - just put in $15. But I realized I hit the damn Regular button by mistake after putting in the gas (I owned an '04 EX Coupe up to just a few weeks ago which took regular).

I realize it is probably nothing, and maybe I should have just refilled the other half of the tank with premium to make up for it - but the guy inside told me to buy octane boost from off their shelf and that would be the same thing. Just used half of it since I didn't fill up. He also acted like Shell gas has all kinds of detergents and additives that their regular gas probably wouldn't do anything bad on a car that says premium required.

Is there a definitive technical answer on what regular gas may do to an Si motor? And if some octane boost on regular gas would make it ok?
 

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octane booster basically adds 3-4 points to the octane. 1 octane is 10 points i believe. So adding octane booster to 89 will bump it to 89.4 essentially
 

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asndragonboii said:
Keep your revs low to prevent knocking until you can refill with your recommeneded octane
Exactly, or you can also fill up the rest of the tank with 93 and that should get you close to 91 because $15 is less than 6 gallons and our tank make 13.5 gallons.
 

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Reg gas IS fine. The engine is continuously adjusting the timing and will simply have less power than if you were running 91. No big deal!
 

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SVB said:
Reg gas IS fine. The engine is continuously adjusting the timing and will simply have less power than if you were running 91. No big deal!
I disagree sir. Our engines are 11:1 compression that is VERY high. Timing can be retarded only so far. I can almost guarantee he will be detonating in VTEC.
 

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SVB said:
Reg gas IS fine. The engine is continuously adjusting the timing and will simply have less power than if you were running 91. No big deal!
Why don't you put some 87 in your Si & come back & tell us it feels fine.
 

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I have an Acura TL ... this car has a J32 engine with the compression ratio 11:1

I hear no pinging... even when I vtec.

I've been putting regular in it for years and the car has no engine troubles at all.

the differences in fuel will affect the car in so small of a fraction, that it's too miniscule to notice even after many years.

Besides new cars aren't meant to break just because u use 87 octane gas...
 

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Just checked the Acura site & it states "Gasoline with an octane number lower than 91 may be used, with reduced performance." on the TL
 

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It is fine to use Reg gas just this time. Do not do it again. It will affect a lot of diff things beside performance. Just don't drive it hard or anything with teh reg gas in there. DO NOT put octane booster in there. It is also proven that octane booster will actually lower your performance.
 

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SiFan4tic said:
still, it wouldn't damage the si, it would just have less power.
It will damage the si eventually. I don't want to list the reason why 87 octane is not good for our engine, its long and complicated
 

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SiFan4tic said:
still, it wouldn't damage the si, it would just have less power.
The J32 & the K20Z3 are two totally different motors with different requirements for fuel.
 
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