is it good to run 93 octane ALL THE TIME??

I do the same thing. high octane is to my understanding used to make the fuel burn more evenly and thus keep engine knock and preignition (uneven detonation) from occurring. In a high performance engine or one with high compression it is necessary. I have heard that as the engine becomes older it helps to avoid detonation as well.
I do not think that there is any detriment to using it (except to your wallet as some think it is a waste and might very well be).

The higher octane burns slower - which reduces the pinging/detonation. There are several theories out there that I have heard- including the slower burn (higher octane) in a car that does not require it will lead to excessive carbon buildup. As a side note I have heard that this build up is why it is thought by some (and perhaps it is true) that higher octane gas has more detergent; it needs it.

@Gronzo - Older engines tend to have more carbon build up, which can increase the chance of pinging. I am reasonably sure the higher octane helps offsets the buildup induced tendancy to detonate.

If you believe the above, it stands to reason that always using higher octane in a vehicle that does not require it could "teach" the vehicle it *needs* the higher octane. (!)

From everything I understand, most people* should probably run the lowest octane they can that does not result in pinging or fall below the manufacturers recommendations. But I dont claim to be a fuel expert other than the higher the octane the slower the burn. (*most people, as in not running nos, turbos, etc.)

Maybe others who do know for sure will chime in.


Kieth

RCRacer94gt said:

Whats the best, not so expencive, way to get rid of carbon buildup?

Click to expand...

Recommended: BG Injection service by an honest mechanic. The injection service is normally a 3 step process. 1) Gas additive. 2) Throttle Body cleaning. and 3) Induction system flush.

This advice comes from personal witness: Price varies *greatly* depending on the dealer. I can not stress enough to make sure you get an HONEST mechanic to do it as flushes and services are often seen as a "quick buck" by mechanics. As an example, the can of throttle cleaner is often only sprayed 1-2 seconds, then tossed, sometimes without even wiping down the throttle body! Yet the can indicates the entire contents should be used, the TB being cleaned thoroughly. (The mechanic will usually not use the whole can because vehicles can sometimes be hard to start with the TB cleaner in the intake - in other words it takes more time.) Similar situation with with the induction flush/cleaner - it is designed to be SLOWLY injected over a 20-30 minute or so run time, yet some guys will open up the valve and flush the whole can through the system in <5 minutes. Point is, these services pay an hour tech time because they take almost an hour to *properly* perform. With shortcuts, the car can be pushed in <15 minutes. If you dont see and trust the mechanic who is to say it was done correctly?? And if it isn't done correctly it isnt worth doing...

Humor Me: An old trick from the carb days, so I have been told, is to get the engine hot and slowly pour a glass of water down the intake while the engine is revved up high. Supposedly the water vaporizes and essentially steams the carbon off. Im in no way suggesting you or anyone else try it; if you get to much water you could seriously damage the engine. And who knows if it even works, those old "wives tales" :headscratch:

Kieth


"My swell check is broke. I mean SPELL CHECK!"

A good way to describe how the octane rating affects performance is the length of burn time. The higher the octane rating, the longer the gasoline burns. Sine the burning of the gasoline causes the chemical to expand, and the expansion pushes the piston down, the action and process becomes clear. A point to consider is watching the Nitro Methane fueled engines. That fuel expands about 1,250 times it's original size when ignited and is generally still burning and expanding while being exhausted, hence the flames coming out of the exhaust.
In a street car, one desires to push the piston down via gas expansion at a rate and length of burn time that results in the smoothest operation. Carbon buildup can result in hotspots that pre-ignite the fuel and cause pinging. Engine timing can cause predetonation too as we "old timers" recall from the ancient "advance 'till it pings then back off" diagnostic instrument free and usually roadside work done on cars we assembled and drove to high school from parts others threw away.

I may not have editied properly and wanted to add this comment. The smart way to maximize the performance of a computer/sensor car is by going to one of the highly trained technicians (such as Eagle AutoSports) whom post on these boards. Todays techs are the best and least costly path towards maximizing performance.

The old trick about pouring water into the intake of a hot engine to knock out the carbon buildup does work. WW2 piston engine aircraft actually had water injection systems. In that case, it was used to prevent detonation. But, I wouldn't use a "glass" to do it. Rather, a plastic bottle would be safer.

I had an uncle who had a PHD in organic chemistry and spent his entire working career in the lab for Shell Oil. This guy knew his s__t about fuels and lubes! I asked the question about using premium fuel in a regular fuel rated motor because it was "better quality". Was told "not so". Same fuel stock. The increase in octane is done with additives. The more additives, the less actual "fuel" you get. If you don't need it, you are wasting your money. In my area, premium is $4.049 a gallon. I'm thinking about backing the timing and fuel pressure down on my '93 LX so I can run 89. Just don't know what compression ratio the Edelbrock heads gave me. The engine was built in 2000, so I've forgotten those details.