Premium Gas
04-18-2005, 09:21 AM
#21
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My Ride: 2005 530i, Jet Black, Black Leather, Automatic, Cold Weather, Sirius Prep and Radio, Premium Package, Xenon Lights.
Here's an interesting read from the "Straight Dope" website:
Dear Cecil:
In this time of high gasoline prices, the Teeming Millions need your guidance (well, at least I do). What is the difference between premium and regular gas, and is this difference worth the extra money? I normally put premium gas into my car because I don't mind paying two or three extra dollars at the pump. Am I being scammed by the gas stations, or is the benefit to my car worth it? --Jeff, via e-mail
Cecil replies:
Not to introduce a radical concept, Jeff, but have you tried reading your owner's manual? If it says to use premium, my advice is to use premium. If it says regular, use regular. The fact that your note indicates no acquaintance with such matters suggests that you may in fact be a scam victim, assuming by this you mean "someone who believes what he hears in commercials." I have a hard time working up much outrage over this deception, since discovering the facts requires so little effort. If you don't mind paying the extra money for no reason, don't expect the oil companies to suffer any pangs accepting it.
In most of the U.S., regular gas has an octane rating of 87, midgrade gas is 89, and premium is 91 or 92. (Octane ratings are lower in the mountain west due to the effects of thin air on internal combustion.) Contrary to widespread belief, the octane rating doesn't indicate how much power the fuel delivers; all grades of gasoline contain roughly the same amount of heat energy. Rather, a higher octane rating means the fuel is less likely to cause your engine to knock or ping. Knock, also known as detonation, occurs when part of the fuel-air mixture in one or more of your car's cylinders ignites spontaneously due to compression, independent of the combustion initiated by the spark plug. (The ideal gas law tells us that a gas heats up when compressed.) Instead of a controlled burn, you get what amounts to an explosion--not a good thing for your engine. To avoid this, high-octane gas is formulated to burn slower than regular, making it less likely to ignite without benefit of spark.
The majority of cars are designed to run on regular gas, and that's what the manuals tell the owners to use. Higher-performance cars often require midgrade or premium gas because their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock. If your car needs high-octane gas, the manual will say so.
Using high-octane gas in a car designed for regular accomplishes little except more rapid combustion of your money. Some refuse to believe this, claiming, for example, that premium gives the family Toyota better mileage or more power. These people are on drugs. Others say premium is purer or contains detergents that will cleanse your engine of uncouth deposits. Likewise misguided thinking--government regulations require detergents in all grades of gasoline. (BP Amoco, I notice, asserts that its premium gasoline contains more detergents than legally required; if you think that's worth 20 extra cents a gallon, be my guest.) Some automotive types claim that using premium in a car designed for regular will make the engine dirtier--something about deposits on the back side of the intake valves. I've also heard that slower-burning high-octane gas produces less power when used in ordinary cars. Believe what you like; the point is, don't assume "premium" means "better."
Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.
You may ask: Don't knock sensors make it hard to tell when an old car needs higher-octane gas? Years ago, when your beater started pinging on grades or under acceleration, that was the sign that carbon had built up in the cylinders, increasing compression, and it was time to switch to high-test. Now the knock sensors compensate, which seemingly might conceal the problem. Don't fret--today's fuel injection systems precisely meter the fuel-air mix, resulting in fewer unburned hydrocarbons and less carbon buildup. If you're still concerned, I'd say it makes more sense to spend $6 on a bottle of carbon clean-out juice than an extra $150 a year on high-priced gas.
--CECIL ADAMS
Dear Cecil:
In this time of high gasoline prices, the Teeming Millions need your guidance (well, at least I do). What is the difference between premium and regular gas, and is this difference worth the extra money? I normally put premium gas into my car because I don't mind paying two or three extra dollars at the pump. Am I being scammed by the gas stations, or is the benefit to my car worth it? --Jeff, via e-mail
Cecil replies:
Not to introduce a radical concept, Jeff, but have you tried reading your owner's manual? If it says to use premium, my advice is to use premium. If it says regular, use regular. The fact that your note indicates no acquaintance with such matters suggests that you may in fact be a scam victim, assuming by this you mean "someone who believes what he hears in commercials." I have a hard time working up much outrage over this deception, since discovering the facts requires so little effort. If you don't mind paying the extra money for no reason, don't expect the oil companies to suffer any pangs accepting it.
In most of the U.S., regular gas has an octane rating of 87, midgrade gas is 89, and premium is 91 or 92. (Octane ratings are lower in the mountain west due to the effects of thin air on internal combustion.) Contrary to widespread belief, the octane rating doesn't indicate how much power the fuel delivers; all grades of gasoline contain roughly the same amount of heat energy. Rather, a higher octane rating means the fuel is less likely to cause your engine to knock or ping. Knock, also known as detonation, occurs when part of the fuel-air mixture in one or more of your car's cylinders ignites spontaneously due to compression, independent of the combustion initiated by the spark plug. (The ideal gas law tells us that a gas heats up when compressed.) Instead of a controlled burn, you get what amounts to an explosion--not a good thing for your engine. To avoid this, high-octane gas is formulated to burn slower than regular, making it less likely to ignite without benefit of spark.
The majority of cars are designed to run on regular gas, and that's what the manuals tell the owners to use. Higher-performance cars often require midgrade or premium gas because their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock. If your car needs high-octane gas, the manual will say so.
Using high-octane gas in a car designed for regular accomplishes little except more rapid combustion of your money. Some refuse to believe this, claiming, for example, that premium gives the family Toyota better mileage or more power. These people are on drugs. Others say premium is purer or contains detergents that will cleanse your engine of uncouth deposits. Likewise misguided thinking--government regulations require detergents in all grades of gasoline. (BP Amoco, I notice, asserts that its premium gasoline contains more detergents than legally required; if you think that's worth 20 extra cents a gallon, be my guest.) Some automotive types claim that using premium in a car designed for regular will make the engine dirtier--something about deposits on the back side of the intake valves. I've also heard that slower-burning high-octane gas produces less power when used in ordinary cars. Believe what you like; the point is, don't assume "premium" means "better."
Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.
You may ask: Don't knock sensors make it hard to tell when an old car needs higher-octane gas? Years ago, when your beater started pinging on grades or under acceleration, that was the sign that carbon had built up in the cylinders, increasing compression, and it was time to switch to high-test. Now the knock sensors compensate, which seemingly might conceal the problem. Don't fret--today's fuel injection systems precisely meter the fuel-air mix, resulting in fewer unburned hydrocarbons and less carbon buildup. If you're still concerned, I'd say it makes more sense to spend $6 on a bottle of carbon clean-out juice than an extra $150 a year on high-priced gas.
--CECIL ADAMS
04-18-2005, 09:50 AM
#22
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Hi,
Something I found: (For 545i and Newer 525, 530)
Valvetronic does not need specific fuel grades or fuel qualities because of its fine atomization of fuel.
Another significant advantage of Valvetronic highly beneficial to the customer is that a Valvetronic engine offers at least the same fuel economy as the most advanced direct-injection petrol engines without the same compromises in terms of emissions. Accordingly, the 316ti is able to do without the elaborate and so far hardly reliable emission management technologies still required today on a direct-injection petrol engine. And it does not require sulfur-free fuel like a direct-injection petrol engine, achieving its superior fuel economy with proven l =1 technology, which allows the Valvetronic engine to run on all commercially available grades of regular petrol. In other words, the customer enjoys all the consumption-related advantages of Valvetronic also when driving in countries without a nationwide supply of sulfur-free fuel. The consumption figures for the 316ti nevertheless relate to the use of premium fuel with an octane rating of 95 RON. Together with its 63-liter (13.9 Imp gal) fuel tank, the 316ti offers a much longer range than its predecessor, with extra-urban fuel consumption in the European EU test cycle of just 5.3 liters for 100 kilometers (53.3 Imp gals). This means that the driver would only have to refuel after a very significant 1,188 kilometers or 737 miles.
Something I found: (For 545i and Newer 525, 530)
Valvetronic does not need specific fuel grades or fuel qualities because of its fine atomization of fuel.
Another significant advantage of Valvetronic highly beneficial to the customer is that a Valvetronic engine offers at least the same fuel economy as the most advanced direct-injection petrol engines without the same compromises in terms of emissions. Accordingly, the 316ti is able to do without the elaborate and so far hardly reliable emission management technologies still required today on a direct-injection petrol engine. And it does not require sulfur-free fuel like a direct-injection petrol engine, achieving its superior fuel economy with proven l =1 technology, which allows the Valvetronic engine to run on all commercially available grades of regular petrol. In other words, the customer enjoys all the consumption-related advantages of Valvetronic also when driving in countries without a nationwide supply of sulfur-free fuel. The consumption figures for the 316ti nevertheless relate to the use of premium fuel with an octane rating of 95 RON. Together with its 63-liter (13.9 Imp gal) fuel tank, the 316ti offers a much longer range than its predecessor, with extra-urban fuel consumption in the European EU test cycle of just 5.3 liters for 100 kilometers (53.3 Imp gals). This means that the driver would only have to refuel after a very significant 1,188 kilometers or 737 miles.
04-18-2005, 01:04 PM
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Originally Posted by Hormazd' date='Apr 18 2005, 07:23 AM
The difference is no more than a dollar a full tank.? The lower octane will retard the timing to prevent knock an ping.? The car will consume more gas so you will probably give back the dollar.
Meanwhile you are lining the cycinder heads and valves with more crap than neccessary lessening engine life.
So kindly ignore that "someone" at BMW and use your own common sense.? You are driving a high compression V8,? what do you think you should pump?
Meanwhile you are lining the cycinder heads and valves with more crap than neccessary lessening engine life.
So kindly ignore that "someone" at BMW and use your own common sense.? You are driving a high compression V8,? what do you think you should pump?
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Just a comment - 545i compression = 10:1, Ford Expedition compression = 9.8:1. Compression is not the full story...
04-18-2005, 01:54 PM
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My Ride: 2004 545i 6 spd Sports Package | NAV | PDC | Logic 7 | BT retrofit | SW V13.3
Originally Posted by tcumbo' date='Apr 18 2005, 09:21 AM
Here's an interesting read from the "Straight Dope" website:
Cecil replies:
but have you tried reading your owner's manual? If it says to use premium, my advice is to use premium.
Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.
--CECIL ADAMS
Cecil replies:
but have you tried reading your owner's manual? If it says to use premium, my advice is to use premium.
Occasionally you get some genius who takes the opposite tack--he spends an extra 10 or 20 grand buying a high-performance car, then decides he's going to save three bucks per tankful using regular instead of premium as specified. He figures as long as the engine doesn't knock he's OK. Wrong, carbon monoxide brain. Car engines nowadays contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.
--CECIL ADAMS
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!
04-18-2005, 05:32 PM
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My Ride: 2005 545i, Black on black. 6spd MT, Nav, sports package.
Good advice.. I'm currently paying about $2.50 for 93 grade fuel. I will keep putting the best I can get.
04-18-2005, 06:24 PM
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My Ride: '06 550i 6 Speed MT, Navigation, PDC, Cold Weather Pkg, Logic7, Prem Pkg, Sport Pkg, Active Steering, Comfort Seats, Comfort Access, HUD, Alpine White on Black Dakota & a Big Grin ;-) <---- On the vessel from Germany...
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'05 545i 6 Speed MT, Navigation, PDC, Cold Weather Pkg, Logic7, Prem Pkg, Sport Pkg, UUC EVOIII SSK, Silver Gray on Black Dakota..... (Buy back by BMW NA)
Originally Posted by BMWJIMT' date='Apr 18 2005, 06:41 AM
In UK unleaded fuel is 85 pence per litre. I did some sums, this works out to $6.06
per US Gallon ( if my calculations are correct! ). What is it there?
per US Gallon ( if my calculations are correct! ). What is it there?
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Yes it is !
04-19-2005, 08:23 AM
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In my neck of the woods the price of premium has stayed a steady 20 cents above regular grade since around US$1.30/gal for regular. So the percentage increase of my premium is actually been less than for those buying regular.
Yeah, that's me lookin' for the silver lining.
Yeah, that's me lookin' for the silver lining.