Is premium gas necessary?

blackboost · 01-10-2007, 09:13 AM

I got into an argument at lunch today with a guy who drives a G35 about gas. He says you should use the lowest octane gas you can that doesn't result in pinging, and he puts 87 in his G35. I said that a car with a highly tuned turbocharged engine like mine requies 93, but I didn't have a good explanation for the rationale. And I clearly don't want to experiment with 87 for the sake of an argument. So do we really need premium gas?

Partysub · 01-10-2007, 09:18 AM

Im not sure about the G35, but I know the STi needs premium. 91 is ok if you are stock but 93 would be better. Tell your friend to read his owners manual.

klaymon · 01-10-2007, 09:18 AM

You can get by with 91 (just ask the guys in CA), but 87 would give you real problems. Why try to skimp on it? Let him argue, just keep feeding your car what it needs.

***Majin*** · 01-10-2007, 09:20 AM

yes. as your car goes into boost, you are at a very high risk of detonating which will (with enough time and/or boost) kill your engine.

higher octane gasoline is more resistant to detonation.

in an emergency, you could add 91 octane (as our California members could tell you more about) but 87 is too low for our cars.

overdose · 01-10-2007, 09:21 AM

he's right, you use the least octane that will not produce knock/ping... and with a turbocharged car like ours, that would be 91 (which really should be 93 to be honest)

***Majin*** · 01-10-2007, 09:21 AM

lots of repeat posts! should've written mine faster.

Muffnbluff · 01-10-2007, 09:21 AM

When you spend 30k+ on a car why not spend the extra $1.00 a fill up to put the correct gas in? I mean you're talking a max of about $50 extra a year to go from 87-91. (I'm referring to the G35 guy, cuz there is no way 87 is the recommended gas for that car)

blackboost · 01-10-2007, 09:24 AM

I would never put anything less than premium in my car, I'm just arguing with a fellow scientist and I couldn't come up with a satisfactory mechanistic reason. So higher octane= more detonation resistance. Not to be too annoying, but does anyone know why?

klaymon · 01-10-2007, 09:26 AM

http://en.wikipedia.org/wiki/Octane_rating

overdose · 01-10-2007, 09:27 AM

Quote:

Originally Posted by blackboost

I would never put anything less than premium in my car, I'm just arguing with a fellow scientist and I couldn't come up with a satisfactory mechanistic reason. So higher octane= more detonation resistance. Not to be too annoying, but does anyone know why?

because higher octane fuel doesn't combust as easily, therefore lower octane fuels are more succeptible to detonation/pre-iginition from heat

Real Deal · 01-10-2007, 09:38 AM

Just read him this:

Quote:

Originally Posted by http://auto.howstuffworks.com/question90.htm

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

Why not pay a little more for gas that is better (less knock) for your engine?

We also have 91 craptane in Seattle, just like Cali does.

***Majin*** · 01-10-2007, 09:38 AM

Quote:

Originally Posted by overdose

because higher octane fuel doesn't combust as easily, therefore lower octane fuels are more succeptible to detonation/pre-iginition from heat

also, IIRC lower octane fuels don't burn as pure or clean as higher octane fuels, leaving carbon deposits on the pistons - this in turn (the carbon deposits) keep retaining heat which will glow red hot (like coal in a blacksmith furnace) which will get hot enough to explode the air/fuel before the spark plug can (detonation).

the higher the octane, the "cleaner" it burns, in turn keeping your pistons "muck" free.

La Mer · 01-10-2007, 09:43 AM

Quote:

Originally Posted by Majin

also, IIRC lower octane fuels don't burn as pure or clean as higher octane fuels, leaving carbon deposits on the pistons - this in turn (the carbon deposits) keep retaining heat which will glow red hot (like coal in a blacksmith furnace) which will get hot enough to explode the air/fuel before the spark plug can (detonation).

the higher the octane, the "cleaner" it burns, in turn keeping your pistons "muck" free.

this is what ive understood in regards to octane.

the higher the octane, the cleaner the fuel burns.

**boondocksaint** · 01-10-2007, 09:50 AM

This should be added to the newbie thread of interest: Why do I have to use Premium Fuel? Good info in this thread.

***Majin*** · 01-10-2007, 10:03 AM

Quote:

Originally Posted by boondocksaint

This should be added to the newbie thread of interest: Why do I have to use Premium Fuel? Good info in this thread.

Newbie Threads of Interest

done. thanks for the suggestion.

01-10-2007, 09:13 AM	#1
blackboost Junior STI Driver Car: 06 STi Fav Mod: borla XR-1 Location: New Haven CT Posts: 88 Join Date: Apr 2006 Trader Rating: (1)	Is premium gas necessary? I got into an argument at lunch today with a guy who drives a G35 about gas. He says you should use the lowest octane gas you can that doesn't result in pinging, and he puts 87 in his G35. I said that a car with a highly tuned turbocharged engine like mine requies 93, but I didn't have a good explanation for the rationale. And I clearly don't want to experiment with 87 for the sake of an argument. So do we really need premium gas? This ad is not endorsed by this member. Please register or login to hide this ad.

01-10-2007, 09:18 AM	#2
Partysub Grassroots STI Racer Car: 04 STi Fav Mod: All of them Location: Wappingers Falls, NY Posts: 508 Join Date: Mar 2006 Trader Rating: (4)	Im not sure about the G35, but I know the STi needs premium. 91 is ok if you are stock but 93 would be better. Tell your friend to read his owners manual.

01-10-2007, 09:18 AM	#3
klaymon S204 Racer Posts: 3,083 Join Date: Jul 2004 Trader Rating: (1)	You can get by with 91 (just ask the guys in CA), but 87 would give you real problems. Why try to skimp on it? Let him argue, just keep feeding your car what it needs.

01-10-2007, 09:20 AM	#4
*Majin* A.X.D. Car: 2004 STi Location: LI, NY Posts: 12,792 Join Date: Apr 2004 Trader Rating: (2)	yes. as your car goes into boost, you are at a very high risk of detonating which will (with enough time and/or boost) kill your engine. higher octane gasoline is more resistant to detonation. in an emergency, you could add 91 octane (as our California members could tell you more about) but 87 is too low for our cars.

01-10-2007, 09:21 AM	#5
overdose Senior STI Driver Car: 2005 WRB STi Fav Mod: roadhead Location: Grand Rapids, MI Posts: 314 Join Date: Dec 2005 Trader Rating: (0)	he's right, you use the least octane that will not produce knock/ping... and with a turbocharged car like ours, that would be 91 (which really should be 93 to be honest)

01-10-2007, 09:21 AM	#7
Muffnbluff DOMINATOR Car: 05 STi OBP Fav Mod: Strut Clunk Location: STL Posts: 5,613 Join Date: May 2005 Trader Rating: (5)	When you spend 30k+ on a car why not spend the extra $1.00 a fill up to put the correct gas in? I mean you're talking a max of about $50 extra a year to go from 87-91. (I'm referring to the G35 guy, cuz there is no way 87 is the recommended gas for that car)

01-10-2007, 09:24 AM	#8
blackboost Junior STI Driver Car: 06 STi Fav Mod: borla XR-1 Location: New Haven CT Posts: 88 Join Date: Apr 2006 Trader Rating: (1)	I would never put anything less than premium in my car, I'm just arguing with a fellow scientist and I couldn't come up with a satisfactory mechanistic reason. So higher octane= more detonation resistance. Not to be too annoying, but does anyone know why?

01-10-2007, 09:26 AM	#9
klaymon S204 Racer Posts: 3,083 Join Date: Jul 2004 Trader Rating: (1)	http://en.wikipedia.org/wiki/Octane_rating

01-10-2007, 09:50 AM	#14
boondocksaint Reasonable Car: Boony's Motown STi Fav Mod: correct grammar Location: D3TR01T Posts: 22,631 Join Date: Jun 2006 Trader Rating: (5)	This should be added to the newbie thread of interest: Why do I have to use Premium Fuel? Good info in this thread.