Premium - 40 cents per gallon more than regular
#16
some cars premium recommended (suggested) other cars premium required. regardless all will run on regular. because you CAN do something does not mean you should. your car, do what you want
#18
Racer
I know my car runs better on 91 octane so that's why I use it. I did a quick calculation a few years ago when I first had the car and felt pretty sure the increase mpg covered off a good portion of the extra cost - so it confirmed it made sense to me to use premium.
The other day I saw 94 octane gas for the first time in Toronto so I filled the tank and the car's computer shows me getting DECREASED miles per gallon. go figure !
The other day I saw 94 octane gas for the first time in Toronto so I filled the tank and the car's computer shows me getting DECREASED miles per gallon. go figure !
#19
^^^ this is actually funny. I've tested this. There are plenty of times I've pumped 91 into cars that only needed 87 and they ran like crap after.
In my case, I've owned so many cars that have gotten 20mpg or lower. I'm at the point where worrying is a lost cause. Gotta pay to play.
And on the get a Prius joke, screw that, buy a diesel! Though, I wouldn't mind a Prius C, that's the only hybrid that makes sense to me.
In my case, I've owned so many cars that have gotten 20mpg or lower. I'm at the point where worrying is a lost cause. Gotta pay to play.
And on the get a Prius joke, screw that, buy a diesel! Though, I wouldn't mind a Prius C, that's the only hybrid that makes sense to me.
#20
Lexus Fanatic
iTrader: (1)
This is a good explanation. The LS430 does have a high compression engine.
Premium Gasoline and Engine Knock
Most internal combustion automobile engines, whether they're four, six or eight cylinders, operate on a four-stroke cycle known as the Otto cycle. The four strokes are: intake, compression, combustion and exhaust. To put it in the simplest of terms, each of the vehicle's pistons moves up and down within a cylinder. As the piston moves to the bottom of the cylinder, a mixture of fuel and air flows in. The piston then moves upward, toward the top of the cylinder, compressing the air and fuel mixture as it does so. Just as the piston reaches the top of the cylinder, that cylinder's spark plug ignites. The spark creates a small, controlled explosion that forces the piston to the bottom of the cylinder. In the final stroke of the cycle, the piston moves upward to push the exhaust gas out of the cylinder. Once the exhaust gas has been pushed out, the entire cycle begins again. For a much more in-depth look at how an internal combustion engine operates, you may want to read How Car Engines Work.
As long as this process works as described above, the engine runs smoothly. But occasionally the pressure of the piston itself will cause the air and gas mixture to ignite prematurely during the compression cycle, creating a smaller, less powerful explosion. This is called preignition and it's the cause of engine knock, the erratic rattling or pinging sound you may occasionally hear underneath your car's hood. A little bit of engine knock isn't necessarily bad for your engine, but it's not desirable, either. It means that your engine isn't running as efficiently as it could be, and left unchecked, it could eventually cause damage. Engine knock reduces your car's performance, too, so you definitely want to avoid it. How, you may ask? Well, low-octane gas is more likely to ignite under the pressure of the piston alone, so it's also more likely to produce engine knock.
Does this mean you should always use high-octane gas? Not necessarily. It really depends on the compression ratio of your engine. This is the ratio of the volume within the cylinder when the piston is at its lowest point to the volume within the cylinder when the piston is at its highest point. The higher the compression ratio, the more compressed the air and fuel mixture becomes and the more likely it is to ignite before it's supposed to due to pressure alone. Cars with a low compression ratio don't need premium gas because there's little danger of the air and fuel mixture igniting improperly. But high-performance engines, which have a high compression ratio, are more prone to preignition and can truly benefit from premium fuel. This would include the engines in most luxury cars.
Modern engines use a device called a knock sensor to detect the rattling and vibration within a cylinder that signals preignition. These sensors send a signal to the vehicle's Engine Control Unit (ECU), sometimes called an Engine Control Module (ECM), which then adjusts the engine's timing -- when the spark plugs fire -- to reduce or prevent the knock. Because these sensors are so effective, cars with knock sensors rarely experience engine knock, even when running on regular unleaded gasoline. However, because the timing is slightly adjusted when low-octane fuel is present, the car's performance and fuel efficiency is diminished slightly, too.
Is the loss in performance dramatic enough to notice? For most people, the answer is probably no. According to one estimate, a car running on regular unleaded instead of premium will take about a half a second longer to accelerate from zero to 60 mph (97 kilometers per hour). Unless you're drag racing, it's unlikely that this will matter. Still, it's conceivable that you might find yourself in a situation where that half second just might matter -- merging safely with highway traffic, for instance. So, it's really up to you to decide if this is important.
Some experts claim that the loss in fuel efficiency when using regular gas in a luxury or high-performance car will be so great that it will actually cancel out the savings you get from buying cheaper low-octane gas. This point is debatable, but you should keep it in mind.
Another reason that people use premium unleaded fuel is that they believe it will keep their car's engine cleaner. This is because some fuel companies advertise that they add special detergents to their higher grades of gas. However, U.S. Environmental Protection Agency regulations require that all grades of gas have detergent in them. Yes, the premium grades often have more detergent, but the lower octane fuels can keep your engine clean, too. If you have reason to believe that an unusual amount of buildup has collected in your engine, simply buy a detergent additive at your local auto store and add it to the tank yourself.
So, unless your owner's manual says that your luxury car "requires" premium gas, it isn't going to hurt your car if you don't use it. And regular gas isn't going to have a significant impact on your engine's performance, either. Basically, it's up to you to decide whether the small impact that it does have is worth the extra cost of premium fuel.
Most internal combustion automobile engines, whether they're four, six or eight cylinders, operate on a four-stroke cycle known as the Otto cycle. The four strokes are: intake, compression, combustion and exhaust. To put it in the simplest of terms, each of the vehicle's pistons moves up and down within a cylinder. As the piston moves to the bottom of the cylinder, a mixture of fuel and air flows in. The piston then moves upward, toward the top of the cylinder, compressing the air and fuel mixture as it does so. Just as the piston reaches the top of the cylinder, that cylinder's spark plug ignites. The spark creates a small, controlled explosion that forces the piston to the bottom of the cylinder. In the final stroke of the cycle, the piston moves upward to push the exhaust gas out of the cylinder. Once the exhaust gas has been pushed out, the entire cycle begins again. For a much more in-depth look at how an internal combustion engine operates, you may want to read How Car Engines Work.
As long as this process works as described above, the engine runs smoothly. But occasionally the pressure of the piston itself will cause the air and gas mixture to ignite prematurely during the compression cycle, creating a smaller, less powerful explosion. This is called preignition and it's the cause of engine knock, the erratic rattling or pinging sound you may occasionally hear underneath your car's hood. A little bit of engine knock isn't necessarily bad for your engine, but it's not desirable, either. It means that your engine isn't running as efficiently as it could be, and left unchecked, it could eventually cause damage. Engine knock reduces your car's performance, too, so you definitely want to avoid it. How, you may ask? Well, low-octane gas is more likely to ignite under the pressure of the piston alone, so it's also more likely to produce engine knock.
Does this mean you should always use high-octane gas? Not necessarily. It really depends on the compression ratio of your engine. This is the ratio of the volume within the cylinder when the piston is at its lowest point to the volume within the cylinder when the piston is at its highest point. The higher the compression ratio, the more compressed the air and fuel mixture becomes and the more likely it is to ignite before it's supposed to due to pressure alone. Cars with a low compression ratio don't need premium gas because there's little danger of the air and fuel mixture igniting improperly. But high-performance engines, which have a high compression ratio, are more prone to preignition and can truly benefit from premium fuel. This would include the engines in most luxury cars.
Modern engines use a device called a knock sensor to detect the rattling and vibration within a cylinder that signals preignition. These sensors send a signal to the vehicle's Engine Control Unit (ECU), sometimes called an Engine Control Module (ECM), which then adjusts the engine's timing -- when the spark plugs fire -- to reduce or prevent the knock. Because these sensors are so effective, cars with knock sensors rarely experience engine knock, even when running on regular unleaded gasoline. However, because the timing is slightly adjusted when low-octane fuel is present, the car's performance and fuel efficiency is diminished slightly, too.
Is the loss in performance dramatic enough to notice? For most people, the answer is probably no. According to one estimate, a car running on regular unleaded instead of premium will take about a half a second longer to accelerate from zero to 60 mph (97 kilometers per hour). Unless you're drag racing, it's unlikely that this will matter. Still, it's conceivable that you might find yourself in a situation where that half second just might matter -- merging safely with highway traffic, for instance. So, it's really up to you to decide if this is important.
Some experts claim that the loss in fuel efficiency when using regular gas in a luxury or high-performance car will be so great that it will actually cancel out the savings you get from buying cheaper low-octane gas. This point is debatable, but you should keep it in mind.
Another reason that people use premium unleaded fuel is that they believe it will keep their car's engine cleaner. This is because some fuel companies advertise that they add special detergents to their higher grades of gas. However, U.S. Environmental Protection Agency regulations require that all grades of gas have detergent in them. Yes, the premium grades often have more detergent, but the lower octane fuels can keep your engine clean, too. If you have reason to believe that an unusual amount of buildup has collected in your engine, simply buy a detergent additive at your local auto store and add it to the tank yourself.
So, unless your owner's manual says that your luxury car "requires" premium gas, it isn't going to hurt your car if you don't use it. And regular gas isn't going to have a significant impact on your engine's performance, either. Basically, it's up to you to decide whether the small impact that it does have is worth the extra cost of premium fuel.
Last edited by Lavrishevo; 11-04-14 at 09:11 AM.
#21
Lexus Test Driver
Also, the European cars are a bit hard to compare to Japanese and American Cars. I believe the lowest octane you can run in Europe is 91. (ROM+MON/2=95+87/2=91*US Octane). So I don't think you would be finding anything lower than 91 unless tuned for lower consumer brands but last i saw, even minimum for VW is 91
#23
Interesting the V8 trucks use 87. I have an appt with my Yota dealer for some work I will ask the Toyota/Lexus master tech his opinion on octane for the V8's. Thanks!
#25
美少女戦士セーラームーン
iTrader: (24)
In my area most gas stations have ethanol in the gas but it's still a 30 to 40 cent difference between regular and premium. Some of the bigger stations have regular with ethanol in addition to pure gas too. Regular with ethanol is a 50 to 75 cent difference. I've even seen a dollar difference a few times, and if you go with 93 octane it's like a $2+ difference from 91.
I always use premium without ethanol but the extra money starts to add up for me since all of my cars use premium now.
I always use premium without ethanol but the extra money starts to add up for me since all of my cars use premium now.
#26
After 10 tanks of fuel....
On my 05 with 60k miles I ran 5 tanks of Sams Hightest (91) @ 15.1 mpg
and then Cheveron (87) low test @ 16.2 mpg
Cheveron is about a nickel more but it works for me here in FL.
and then Cheveron (87) low test @ 16.2 mpg
Cheveron is about a nickel more but it works for me here in FL.
#27
Intermediate
The octane rating is basically a measure of how readily gasoline combusts under compression in the combustion chamber. The lower the octane, the easier it is to burn at any given pressure. If the motor compression is higher as in racing engines, too low of octane rating will cause premature detonation aka pinging or knocking in the engine which can cause engine damage. That being said, an engine will perform its best on the lowest octane possible without developing knock. Now modern fuel injected engines will avoid this dangerous pinging by retarding the timing using a knock detection sensor and that is why a performance decrease is felt on higher compression engines running low octane. If you feel this decrease in performance running 87, the next higher octane should be tried until the desired result is achieved.
#29
Pole Position
Alrighty. There's a lot of wondering in this thread and that shouldn't be the case. An answer exists and it's that:
87 octane is safe for our cars. But not optimal for power or fuel economy.
My rule of thumb is that I use 89 octane unless premium is within 15 cents a gallon, and as long as 89 octane is within 20 cents a gallon of 87 octane.
Basically, an engine's octane requirement is a function of its compression ratio and its ignition timing.
Ignition timing was the starting point of electronic engine control, and Japan has forgotten more about electronic engine controls than the rest of the world has learned. Our ECUs estimate fuel quality a few hundred times a second and use the information to adjust the ignition timing and camshaft phasing on the fly to achieve optimal combustion. They can absolutely handle 87 octane.
Around the world, fuel economy varies radically. And Toyota makes sure that the engine won't grenade if you run a few gallons of 83 octane "gas" through it. Obviously that fuel isn't ideal though.
Secondly, our engines do have a modestly high compression ratio at 10.5:1. Mazda runs 13.1:1 compression ratios on 86/87 octane. The ratio of 10.5:1 won't perform optimally on 87 octane (89 octane is basically the minimum for excellent combustion performance at the 10.5:1 ratio) but they can hack it. And it becomes even easier on the engines when the ignition is adjusted for the fuel quality.
In my experience, I've found that 91 octane gets about 15% better mileage than 87 octane, and 89 octane gets ~10% better milage. So the question you should be asking is "which is the most cost effective?"
If you really wanted, you could go find 94 octane or 101 octane, and pay $10/gallon to test it out. You'll find our engines don't do much with the extra octane.
The compression ratios and electronic controls that make our engines work with 87 octane don't lend themselves to high performance on abnormally high octane gases. You'll notice more of a difference going from 87 to 89 octane than 89 to 91 octane. And you probably won't notice a difference between 91 and 93, and there will be no difference, or even a decline in performance from 93 octane to 100+ octane.
At some point, our engines can't squish the fuel and air mixture more, and can't advance the ignition any more, and can't make more power. And that's probably at 93 octane.
I have a 125cc Honda Grom with an 8.7:1 compression ratio. Its top speed is about 60 mph when I run 87 octane. If I run 93 octane, it only goes about 57 mph.
How could that be?
Well, it can squish the 87 octane fuel air mixture really well and ignite it just after the piston moves to top dead center. Higher octanes resist detonation and the spark plug has to fire well before the piston reaches the top to make sure the flame spreads throughout the cylinder. This reduces the capacity for power and drops the efficiency of the engine.
87 octane is safe for our cars. But not optimal for power or fuel economy.
My rule of thumb is that I use 89 octane unless premium is within 15 cents a gallon, and as long as 89 octane is within 20 cents a gallon of 87 octane.
Basically, an engine's octane requirement is a function of its compression ratio and its ignition timing.
Ignition timing was the starting point of electronic engine control, and Japan has forgotten more about electronic engine controls than the rest of the world has learned. Our ECUs estimate fuel quality a few hundred times a second and use the information to adjust the ignition timing and camshaft phasing on the fly to achieve optimal combustion. They can absolutely handle 87 octane.
Around the world, fuel economy varies radically. And Toyota makes sure that the engine won't grenade if you run a few gallons of 83 octane "gas" through it. Obviously that fuel isn't ideal though.
Secondly, our engines do have a modestly high compression ratio at 10.5:1. Mazda runs 13.1:1 compression ratios on 86/87 octane. The ratio of 10.5:1 won't perform optimally on 87 octane (89 octane is basically the minimum for excellent combustion performance at the 10.5:1 ratio) but they can hack it. And it becomes even easier on the engines when the ignition is adjusted for the fuel quality.
In my experience, I've found that 91 octane gets about 15% better mileage than 87 octane, and 89 octane gets ~10% better milage. So the question you should be asking is "which is the most cost effective?"
If you really wanted, you could go find 94 octane or 101 octane, and pay $10/gallon to test it out. You'll find our engines don't do much with the extra octane.
The compression ratios and electronic controls that make our engines work with 87 octane don't lend themselves to high performance on abnormally high octane gases. You'll notice more of a difference going from 87 to 89 octane than 89 to 91 octane. And you probably won't notice a difference between 91 and 93, and there will be no difference, or even a decline in performance from 93 octane to 100+ octane.
At some point, our engines can't squish the fuel and air mixture more, and can't advance the ignition any more, and can't make more power. And that's probably at 93 octane.
I have a 125cc Honda Grom with an 8.7:1 compression ratio. Its top speed is about 60 mph when I run 87 octane. If I run 93 octane, it only goes about 57 mph.
How could that be?
Well, it can squish the 87 octane fuel air mixture really well and ignite it just after the piston moves to top dead center. Higher octanes resist detonation and the spark plug has to fire well before the piston reaches the top to make sure the flame spreads throughout the cylinder. This reduces the capacity for power and drops the efficiency of the engine.