Well you ARE driving a turbocharged car, right? Higher octane also helps by burning slower than lower octane fuel. This means that it'll combust somewhere ATDC unless you've adjusted your timing. Hmm, I don't think I'm making any sense.

If you have a B series you NEED to run 91+

You might notice a difference in the way your engine runs on premium unleaded, but I assure you that if the motor is a mostly stock Honda mill then you are not gaining any performance with the expensive juice.

What does octane do? It raises the temperature at which the fuel ignites thereby delaying the full combustion of the a/f mixture. This is something desirable in a high compression or force inducted motor (a law of physics is that when you compress a gas the temperature increases, so in both the preceding cases the a/f mixture will be at a higher temperature and prone to igniting too quickly unless you run a higher octane fuel). In a car capable of running without pre-detonation on mid- or low-grade fuel you will not see any benefit and may actually see a drop in power as a result of running high octane fuel. Why? Because you end up pushing back the point at which the a/f mixture combusts past the point where the piston is just barely past top dead center...as a result you do not get the full benefit of the combusting gasses pushing against the piston top.

What about cars with knock sensors that advance timing as far as possible before encountering knock? Well, higher octane and advanced ignition timing result in the same thing as lower octane and retarded ignition timing. The goal is to obtain the optimal timing of the full combustion of the a/f mixture relative to the position of the piston. Increasing octane pushes that point back, and advancing the ignition timing pushes that point forward. In the end it equals out. Also most of these systems have a finite range of adjustment and if you exceed the computer's ability to advance the timing, then you lose power.

Why did your car behave differently on higher octane? Because the full combustion was occuring after the optimal point relative to the position of the piston (probably). You may see lower EGT's (although the opposite is also likely) and head temps, but these are just further indications that you are not getting the most out of the fuel's energy store.

So if you don't mind paying $.30 more per gallon for less power, then go for it. You will not be hurting your injectors or anything. But if you are more interested in getting the most power out of you motor, then don't use a higher octane fuel than you need. Don't believe the hype.

If you have a B series you NEED to run 91+
Not necessarily, I have run 89 and 93 octanes in a b16a1 and they both gave me the same whp numbers. 142 whp.

btw, so fla has good octanes!


[Modified by DarkKnight[DMD], 11:35 AM 9/11/2002]

We get 94 Octane here, all over the place

well in the manual for my 99 Si/SiR and 02 Type S it says use 91+...using a lower octane will result in lowered performance and/or detationation engine pinging

also do you mean B16A? I wasnt aware there was an A1, only A2 and A3.


[Modified by WR93EG, 2:31 PM 9/11/2002]