Premium Gas Question
06-18-2005, 03:13 PM
#1
Cruisin'
Thread Starter
Join Date: Feb 2005
Age: 80
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Premium Gas Question
Recently i filled my car w regular gas. (I just forgot and I asked for regular).
The car ran fine w no pings and the acceleration seemed fine.
I used to follow the guideline of 'Using the cheapest grade gas that didn't produce a ping'. But w the Acura I wasn't sure.
Is this guideline valid w all the advanced valve timing etc in the RL??
The car ran fine w no pings and the acceleration seemed fine.
I used to follow the guideline of 'Using the cheapest grade gas that didn't produce a ping'. But w the Acura I wasn't sure.
Is this guideline valid w all the advanced valve timing etc in the RL??
06-18-2005, 05:16 PM
#2
Retired MOD
Join Date: Mar 2001
Location: Fredericksburg, VA
Age: 46
Posts: 3,995
Likes: 0
Received 1 Like
on
1 Post
The car will automatically adjust. Knock sensors detect knocking in a matter of milliseconds and adjust the timing.
Here is all you need to know:
Demystifying Octane Ratings
A gasoline’s octane rating quantifies its resistance to knocking and pinging. These two sounds are caused by abnormal combustion, which robs power and can damage an engine. Knocking and pinging are basically the same thing; knocking is louder and represents a more serious condition. When they occur, it is during acceleration, though higher engine speeds tend to drown them out. Knocking sounds like someone repeatedly rapping the engine with a hammer, and the quieter pinging resembles marbles being shaken inside a tin can.
Most gas stations offer a choice of three unleaded fuels, each with a different octane rating: 87, 89 or 93. Which one is right for your car? That depends on the type of engine you have.
Many conditions in the engine itself can cause or promote combustion anomalies, but when all other factors are equal, gasoline with a higher octane rating is more resistant to knocking and pinging than a lower-octane fuel. So why doesn’t everyone just use high-octane gasoline? Because it is more expensive, and there is no advantage whatsoever in using premium gasoline in a car that doesn’t specifically require it. At one time, only premium gasoline included additives that prevent fuel-injector clogging; now, all grades are basically the same in this regard.
If your car requires high-octane gasoline and you habitually use regular gas because the engine exhibits no sign of knock, you’re outsmarting yourself. Most modern, computer-controlled engines include a knock sensor that detects knock and retards the ignition timing, causing the spark plugs to fire slightly later in the cycle. This typically prevents abnormal combustion and knock, which allows vehicles specified for premium fuel to run on lower-grade gasoline if it is all that’s available. While this removes the immediate hazard, it’s a bad idea to make a habit of running a vehicle on gasoline of lower-than-recommended octane. Retarding the spark causes a richer fuel/air mixture, which decreases fuel economy, increases emissions, causes the engine to run hotter, and reduces the longevity of both the engine itself and the catalytic converter. The money you save by pumping low-grade fuel into a car that demands higher octane is lost anyway, in decreased fuel economy and possibly gradual damage.
Your vehicle’s owner’s manual usually recommends an octane rating in terms of an Antiknock Index (AKI), which also is posted on gasoline pumps. The AKI is the average of two ratings determined in a laboratory: the Research Octane Number (RON), which corresponds with low-speed, mild-knocking conditions, and the Motor Octane Number (MON), which covers high-speed, high-temperature knocking conditions and part-throttle operation.
In general, three grades of gasoline are available in the United States: regular (AKI = 87), midgrade (AKI = 89) and premium (AKI = 91 to 94). The posted gasoline AKIs are lower in the Rocky Mountain states because less octane is needed at higher altitudes. Motorists whose cars require 91 octane fuel may find themselves at filling stations that offer only 89 and 93 octane, but nothing in between. In these cases, the options are to pay more for the 93 octane or to fill the tank halfway with 93 and the rest with 89. The resulting gasoline mixture, just like the average of their two AKI numbers, will equal 91 octane.
Premium fuel is mostly required by engines with high compression ratios and/or turbochargers or superchargers, for reasons explained in What Causes Knocking and Pinging.
Aftermarket Octane Boosters
Like higher-octane fuel from the pump, aftermarket octane booster additives you can buy in a store will not improve performance if you use the correct gasoline grade to begin with. It likely will benefit only an older car with a high-compression engine. There are three basic types of octane boosters:
Aromatic hydrocarbons, such as oxylene and toluene, which provide only a marginal octane increase.
Alcohols, such as methanol or ethanol, which are the most common and provide only a bit more boost.
Metallic octane boosters that contain methyl-cyclopentadienyl manganese (MMT), which are by far the most effective.
How Gasoline Octane Is Determined
A gasoline blend’s octane rating is determined by combusting it in a one-cylinder test engine and comparing its antiknock performance to that of standard, measurable reference fuels. The test engine allows the administrator to vary the compression and fuel/air mixture ratios — two factors that affect knock — with the goal of inducing a standard knock intensity, as measured by a knock meter.
All gasoline is a mixture of different hydrocarbons (hydrogen and carbon molecules of various configurations) ending in “ane,” as in hexane, nonane and dodecane. Two such hydrocarbons represent each end of the octane scale: Iso-octane has an octane rating of 100 and heptane a rating of 0. The technicians run the same engine on a blend of these two fuels and vary the ratio of each to the other until the knock intensity matches that of the gasoline under test. The percentage of iso-octane in that mixture — say, 93 percent iso-octane to 7 percent heptane — is the tested gasoline’s AKI rating: 93 octane.
How Gasoline Octane Is Controlled
Between 1923 and 1986, when leaded gas was sold in the United States, the accepted method of boosting octane ratings was to add tetraethyl lead (TEL) to gasoline. The sale of leaded gasoline in the United States is now prohibited because it contaminates the precious metals used in catalytic converters and it is considered harmful to people and the environment. Leaded gasoline is still used in less-developed parts of the world, because it’s cheaper to produce, and many of the older vehicles found in these countries require it for its additional lubrication properties.
Iso-octane would seem the perfect additive to vary gasoline octane ratings, but it is far too expensive. Refiners now use other metal-, alcohol- or hydrocarbon-based elements to vary octane in gasoline blends. The oxygenates added to create cleaner-burning reformulated gasoline (RFG), mainly methyl tertiary-butyl ether (MTBE) and ethanol, also boost octane. To learn more about reformulated gas and why it adds cost, see Oxygenates and Reformulated Gas.
Here is all you need to know:
Demystifying Octane Ratings
A gasoline’s octane rating quantifies its resistance to knocking and pinging. These two sounds are caused by abnormal combustion, which robs power and can damage an engine. Knocking and pinging are basically the same thing; knocking is louder and represents a more serious condition. When they occur, it is during acceleration, though higher engine speeds tend to drown them out. Knocking sounds like someone repeatedly rapping the engine with a hammer, and the quieter pinging resembles marbles being shaken inside a tin can.
Most gas stations offer a choice of three unleaded fuels, each with a different octane rating: 87, 89 or 93. Which one is right for your car? That depends on the type of engine you have.
Many conditions in the engine itself can cause or promote combustion anomalies, but when all other factors are equal, gasoline with a higher octane rating is more resistant to knocking and pinging than a lower-octane fuel. So why doesn’t everyone just use high-octane gasoline? Because it is more expensive, and there is no advantage whatsoever in using premium gasoline in a car that doesn’t specifically require it. At one time, only premium gasoline included additives that prevent fuel-injector clogging; now, all grades are basically the same in this regard.
If your car requires high-octane gasoline and you habitually use regular gas because the engine exhibits no sign of knock, you’re outsmarting yourself. Most modern, computer-controlled engines include a knock sensor that detects knock and retards the ignition timing, causing the spark plugs to fire slightly later in the cycle. This typically prevents abnormal combustion and knock, which allows vehicles specified for premium fuel to run on lower-grade gasoline if it is all that’s available. While this removes the immediate hazard, it’s a bad idea to make a habit of running a vehicle on gasoline of lower-than-recommended octane. Retarding the spark causes a richer fuel/air mixture, which decreases fuel economy, increases emissions, causes the engine to run hotter, and reduces the longevity of both the engine itself and the catalytic converter. The money you save by pumping low-grade fuel into a car that demands higher octane is lost anyway, in decreased fuel economy and possibly gradual damage.
Your vehicle’s owner’s manual usually recommends an octane rating in terms of an Antiknock Index (AKI), which also is posted on gasoline pumps. The AKI is the average of two ratings determined in a laboratory: the Research Octane Number (RON), which corresponds with low-speed, mild-knocking conditions, and the Motor Octane Number (MON), which covers high-speed, high-temperature knocking conditions and part-throttle operation.
In general, three grades of gasoline are available in the United States: regular (AKI = 87), midgrade (AKI = 89) and premium (AKI = 91 to 94). The posted gasoline AKIs are lower in the Rocky Mountain states because less octane is needed at higher altitudes. Motorists whose cars require 91 octane fuel may find themselves at filling stations that offer only 89 and 93 octane, but nothing in between. In these cases, the options are to pay more for the 93 octane or to fill the tank halfway with 93 and the rest with 89. The resulting gasoline mixture, just like the average of their two AKI numbers, will equal 91 octane.
Premium fuel is mostly required by engines with high compression ratios and/or turbochargers or superchargers, for reasons explained in What Causes Knocking and Pinging.
Aftermarket Octane Boosters
Like higher-octane fuel from the pump, aftermarket octane booster additives you can buy in a store will not improve performance if you use the correct gasoline grade to begin with. It likely will benefit only an older car with a high-compression engine. There are three basic types of octane boosters:
Aromatic hydrocarbons, such as oxylene and toluene, which provide only a marginal octane increase.
Alcohols, such as methanol or ethanol, which are the most common and provide only a bit more boost.
Metallic octane boosters that contain methyl-cyclopentadienyl manganese (MMT), which are by far the most effective.
How Gasoline Octane Is Determined
A gasoline blend’s octane rating is determined by combusting it in a one-cylinder test engine and comparing its antiknock performance to that of standard, measurable reference fuels. The test engine allows the administrator to vary the compression and fuel/air mixture ratios — two factors that affect knock — with the goal of inducing a standard knock intensity, as measured by a knock meter.
All gasoline is a mixture of different hydrocarbons (hydrogen and carbon molecules of various configurations) ending in “ane,” as in hexane, nonane and dodecane. Two such hydrocarbons represent each end of the octane scale: Iso-octane has an octane rating of 100 and heptane a rating of 0. The technicians run the same engine on a blend of these two fuels and vary the ratio of each to the other until the knock intensity matches that of the gasoline under test. The percentage of iso-octane in that mixture — say, 93 percent iso-octane to 7 percent heptane — is the tested gasoline’s AKI rating: 93 octane.
How Gasoline Octane Is Controlled
Between 1923 and 1986, when leaded gas was sold in the United States, the accepted method of boosting octane ratings was to add tetraethyl lead (TEL) to gasoline. The sale of leaded gasoline in the United States is now prohibited because it contaminates the precious metals used in catalytic converters and it is considered harmful to people and the environment. Leaded gasoline is still used in less-developed parts of the world, because it’s cheaper to produce, and many of the older vehicles found in these countries require it for its additional lubrication properties.
Iso-octane would seem the perfect additive to vary gasoline octane ratings, but it is far too expensive. Refiners now use other metal-, alcohol- or hydrocarbon-based elements to vary octane in gasoline blends. The oxygenates added to create cleaner-burning reformulated gasoline (RFG), mainly methyl tertiary-butyl ether (MTBE) and ethanol, also boost octane. To learn more about reformulated gas and why it adds cost, see Oxygenates and Reformulated Gas.
Thank You
06-20-2005, 05:35 PM
#6
Instructor
Originally Posted by hondamore
Thanks Bitium - an outstanding post!!
Bitium - best explaination I have ever seen regarding High Octane gasoline. I had recently stuck with the "lower emissions" explaination as to why I purchase 93 octane, but will now add your other points to my response.
Thanks again.
very informative. Thanks for the education 
Trending Topics
03-05-2009, 03:12 PM
#8
Burning Brakes
Since the management has linked to this thread, I'll add a 2009 anecdotal update: after alternating tanks of mid and high grade gas and driving my regular commute, I can tell you I demonstrably save money using Premium fuel. It's a 2.3 mpg difference averaged across 6 tanks total.
Plus, chicks dig me for going hi-test.
Plus, chicks dig me for going hi-test.
03-05-2009, 08:20 PM
#11
Senior Moderator
I follow the manufacturer's instructions. 
Premium it is!
I accidentally put 87 in my car two months ago--I was REALLY tired that day--and took a significant mileage hit....I got 15 mpg in my mixed driving.
Premium it is!I accidentally put 87 in my car two months ago--I was REALLY tired that day--and took a significant mileage hit....I got 15 mpg in my mixed driving.
03-06-2009, 07:32 PM
#12
Pro
When I first bought my car, I put 87 in my car for the first tank (I didnt know). When idling, it was rough and I thought the car needed to be taken back to the dealer. I put 93 in it and a one time shot of techron, because when I stepped on the gas, the cars exhaust stunk.
After the tank with techron and putting 93 in it, she runs SMOoooth!
(and doesnt stink any more).
After the tank with techron and putting 93 in it, she runs SMOoooth!
(and doesnt stink any more).
Thread
Thread Starter
Forum
Replies
Last Post
Zonian22
Member Cars for Sale
3
11-14-2015 01:20 PM
