What's your thoughts on premium gas
10-30-2014, 09:01 PM
#1
Thread Starter
Join Date: Oct 2014
Location: Louisiana
Posts: 7
What's your thoughts on premium gas
Drive a 2002 gt v8 4.6l only mods I have are catback exaust bbk Cai and bbk throttle body. Would it be a waste of my money to put premium gas in the tank even though it doesn't call for it? Heard a lot of mixed opinions
10-31-2014, 02:25 PM
#3
2nd Gear Member
Join Date: Oct 2011
Location: Missouri
Posts: 227
^^^ This.
You only need to run premium fuel if your engine is tuned for it.
Regardless of what you have heard, octane rating is purely a measure of a fuels ability to resist autoignition. Nothing more. It is NOT a measure of the energy content of the fuel. For spark ignited engines there point in the combustion cycle where the maximum in cylinder pressure occurs produces the most torque (typically around 16 deg. ATDC). See the spark plug actually fires slightly before TDC. That way just after TDC the "explosion" has already started and there is maximum pressure in the cylinder to push the piston down (making maximum power). Because of MANY MANY reasons, most engines are not able to operate at this point and maximum in cylinder pressure occurs after this point.
Once the spark fires and combustion starts, the last area of fuel/air mixture to be consumed is the area around the piston skirt above the rings. This area is called the end gas. If spark timing is set too early in the cycle, in cylinder pressures and temperatures get higher and this end gas has the possibility to autoignite (causing knock). To start this spark earlier (advance the timing) you need the fuel to have more of a resistance to autoignition (higher octane). By starting the spark earlier, you get closer to that maximum output for the engine.
So unless you have a tune which advances spark timing to utilize the extra octane, it is literally doing nothing for you. A reason you hear of race cars running 100+ octane is because this allows them to run a higher compression ratio. Higher octane fuel->higher resistance to autoignition->ability to run higher compression ratio. Since compression ratio is a direct multiplier to the efficiency of the engine, this greatly affects power output of the engine.
So in short. If you're running the stock tune, run 87 octane. If you're running an aftermarket tune, run whatever it calls for and NEVER anything lower.
EDIT: TDC= Top Dead Center
You only need to run premium fuel if your engine is tuned for it.
Regardless of what you have heard, octane rating is purely a measure of a fuels ability to resist autoignition. Nothing more. It is NOT a measure of the energy content of the fuel. For spark ignited engines there point in the combustion cycle where the maximum in cylinder pressure occurs produces the most torque (typically around 16 deg. ATDC). See the spark plug actually fires slightly before TDC. That way just after TDC the "explosion" has already started and there is maximum pressure in the cylinder to push the piston down (making maximum power). Because of MANY MANY reasons, most engines are not able to operate at this point and maximum in cylinder pressure occurs after this point.
Once the spark fires and combustion starts, the last area of fuel/air mixture to be consumed is the area around the piston skirt above the rings. This area is called the end gas. If spark timing is set too early in the cycle, in cylinder pressures and temperatures get higher and this end gas has the possibility to autoignite (causing knock). To start this spark earlier (advance the timing) you need the fuel to have more of a resistance to autoignition (higher octane). By starting the spark earlier, you get closer to that maximum output for the engine.
So unless you have a tune which advances spark timing to utilize the extra octane, it is literally doing nothing for you. A reason you hear of race cars running 100+ octane is because this allows them to run a higher compression ratio. Higher octane fuel->higher resistance to autoignition->ability to run higher compression ratio. Since compression ratio is a direct multiplier to the efficiency of the engine, this greatly affects power output of the engine.
So in short. If you're running the stock tune, run 87 octane. If you're running an aftermarket tune, run whatever it calls for and NEVER anything lower.
EDIT: TDC= Top Dead Center
Last edited by unitedwestang; 05-06-2015 at 12:00 PM.
10-31-2014, 02:27 PM
#4
2nd Gear Member
Join Date: Oct 2011
Location: Missouri
Posts: 227
Additionally, though, with the mods you've listed, you may want to consider getting a tune to make the most of what you've got. Bama tunes through Americanmuscle would be perfect for what you have. And its free tunes for life with them if you buy your tuner from them. So if you add anymore mods you just email them and they send you a revised tune.
Last edited by unitedwestang; 10-31-2014 at 02:29 PM.
11-01-2014, 05:54 AM
#5
2nd Gear Member
Join Date: Apr 2009
Location: GA
Posts: 191
I run premium in mine as I have a canned race tune I run. I would say that I'm fortunate to have an ethanol free station so I get 100% gas so it does allow me to play with the settings.
We the adulterated fuels they vary in alky content from station to station. And with that messing around the the settings would be more difficult. I need to get off my *** and get a dyno tune but for now I believe I have it the best I can get till then.
We the adulterated fuels they vary in alky content from station to station. And with that messing around the the settings would be more difficult. I need to get off my *** and get a dyno tune but for now I believe I have it the best I can get till then.
11-20-2014, 03:51 AM
#10
Banned
Join Date: Apr 2014
Location: North
Posts: 130
There is a lot of misinformation out there, lots of 'myths' about 'myths' almost makes ya think lies are spread by mechanics so they get more business, but from what I've seen my cars run much better on 89 octane. I won't even get into the fuel system cleaner deal (if you don't believe they help, just take out a spark plug and use a scope to take a pic before and after.)
Also I have noticed many of the people who say "there's not benefit to higher octane" usually run higher octane on their own stock 87 vehicles. Kinda like those parents who tell other people's children "oh community college is just fine" but practically murder others to make sure their own kids get into good colleges. I hate people and society so much.
Also I have noticed many of the people who say "there's not benefit to higher octane" usually run higher octane on their own stock 87 vehicles. Kinda like those parents who tell other people's children "oh community college is just fine" but practically murder others to make sure their own kids get into good colleges. I hate people and society so much.
Last edited by RenGen; 11-20-2014 at 04:05 AM.