Premium gas, or?

[terrypm]

from Wikipedia:

Ethanol contains approx. 34% less energy per unit volume than gasoline, and therefore in theory, burning pure ethanol in a vehicle will result in a 34% reduction in miles per US gallon, given the same fuel economy, compared to burning pure gasoline. Since ethanol has a higher octane rating, the engine can be made more efficient by raising its compression ratio. In fact using a variable turbocharger, the compression ratio can be optimized for the fuel being used, making fuel economy almost constant for any blend.[25][26] For E10 (10% ethanol and 90% gasoline), the effect is small (~3%) when compared to conventional gasoline,[55] and even smaller (1-2%) when compared to oxygenated and reformulated blends.[56] For E85 (85% ethanol), the effect becomes significant. E85 will produce lower mileage than gasoline, and will require more frequent refueling. Actual performance may vary depending on the vehicle. Based on EPA tests for all 2006 E85 models, the average fuel economy for E85 vehicles resulted 25.56% lower than unleaded gasoline.[57] The EPA-rated mileage of current USA flex-fuel vehicles[58] should be considered when making price comparisons, but E85 is a high performance fuel, with an octane rating of about 94-96, and should be compared to premium.[59

[WolfpackS2k]

Originally Posted by MRZ415

As of tonight I saw prices near me as
$4.49 for 87
$4.59 for 89
$4.69 for 91...

and $4.29 for Diesel #2 (w00t for my tdi at least for now )

yeah have fun with that over in the land of [s]crazy people[/s] California.

Here in Raleigh, NC premium 93 is around $3.89 most places

[thill]

Premium at Costco and Sams is $3.68 right now outside of Minneapolis.

[Allch Chcar]

Originally Posted by ngabdala

Too much risk with unleaded and you are going to have to use more gas just to get your car to move.

It's perfectly fine to run regular, knock sensors are standard now. But since the FA20 is designed for Premium it's going to run less efficient on regular making the end cost the same or negligible.

OP, run the highest grade unleaded 93 AKI octane if you can, you won't regret it.

Originally Posted by terrypm

I wonder what the owners manual states about using 100% gas or the blended gas with 10% ethanol? I know the ethanol blended gas has less energy than 100% gas so you get worse gas mileage with it.

Gas prices near me:

10% ethanol
87- $3.28
89- 3.38
91- 3.52

100% gas
87- 3.54
89- 3.79
91- 3.90

In some states, only premium grades can be Ethanol free. The Twins' manual(it's like page 272 or something) says 10% Ethanol is perfectly fine, it's even tuned specifically for it, but it says to not run anything beyond that. Disappointing if, like me, you want to run E85 but that's normal for all sporty cars.

Originally Posted by terrypm

from Wikipedia:

Ethanol contains approx. 34% less energy per unit volume than gasoline, and therefore in theory, burning pure ethanol in a vehicle will result in a 34% reduction in miles per US gallon, given the same fuel economy, compared to burning pure gasoline. Since ethanol has a higher octane rating, the engine can be made more efficient by raising its compression ratio. In fact using a variable turbocharger, the compression ratio can be optimized for the fuel being used, making fuel economy almost constant for any blend.[25][26] For E10 (10% ethanol and 90% gasoline), the effect is small (~3%) when compared to conventional gasoline,[55] and even smaller (1-2%) when compared to oxygenated and reformulated blends.[56] For E85 (85% ethanol), the effect becomes significant. E85 will produce lower mileage than gasoline, and will require more frequent refueling. Actual performance may vary depending on the vehicle. Based on EPA tests for all 2006 E85 models, the average fuel economy for E85 vehicles resulted 25.56% lower than unleaded gasoline.[57] The EPA-rated mileage of current USA flex-fuel vehicles[58] should be considered when making price comparisons, but E85 is a high performance fuel, with an octane rating of about 94-96, and should be compared to premium.[59

Ethanol has less energy per gallon, so it's more expensive than you would think, but it makes more power. E85 is the bees' knees for hotrods.

BTW, the EPA does not test MPG on any Ethanol content. They calculate the MPG for all cars based on BTU content.

[Subie]

Originally Posted by Allch Chcar

It's perfectly fine to run regular, knock sensors are standard now. But since the FA20 is designed for Premium it's going to run less efficient on regular making the end cost the same or negligible.

I'm sorry but that's not true. Yes, it does have knock sensors, and it WILL pull timing, but that can only do so much. The engine may still knock under certain driving conditions which will damage it over time. The FA20/4U-GSE requires premium fuel. It's exactly what it sounds like.

[Allch Chcar]

Originally Posted by Subie

I'm sorry but that's not true. Yes, it does have knock sensors, and it WILL pull timing, but that can only do so much. The engine may still knock under certain driving conditions which will damage it over time. The FA20/4U-GSE requires premium fuel. It's exactly what it sounds like.

I must ask you to prove it then. Nothing that I've seen or read says that a factory ECU cannot compensate enough for regular grade. I have even seen people run regular on "premium only" engines for many years without a problem.

Edit: Since it's common knowledge and you are refuting it. I did make the initial statement so I will add that you can do a quick search for "can you run regular in a premium engine" and find this.
Why use premium gas when regular will do?

The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.

Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.

I still say run the highest grade available. It's not like it's expensive.

[Subie]

Originally Posted by Allch Chcar

I must ask you to prove it then. Nothing that I've seen or read says that a factory ECU cannot compensate enough for regular grade. I have even seen people run regular on "premium only" engines for many years without a problem.

I can't personally prove it, but reading an article such as this one will provide insight into the difference between "premium recommended" and "premium required."

[DeeezNuuuts83]

Originally Posted by Allch Chcar

I have even seen people run regular on "premium only" engines for many years without a problem.

But on what kinds of cars? Some can deal with it better, especially if they are not highly tuned with pretty high compression ratios or boosted.

A friend of mine who used to work at Enterprise Rent-A-Car said that they never put anything over 87 octane in their cars, but again, it's not as if they have sports cars in their regular inventory. This came up in discussion when he and I rented a Mercedes E350 for a trip. And again, the E350 isn't a slouch, but it doesn't have the most technologically advanced engine on the market.

[Allch Chcar]

Originally Posted by Subie

I can't personally prove it, but reading an article such as this one will provide insight into the difference between "premium recommended" and "premium required."

That list doesn't include the Twins. I'm going to check the manual again since I know it covered this.

[Subie]

Originally Posted by Allch Chcar

That list doesn't include the Twins. I'm going to check the manual again since I know it covered this.

Please report back when you've done so.

[iDriveFast]

They made the car to run on premium so use premium. Its not like the genesis coupe where they actually tell you that you can use regular or premium.

[Allch Chcar]

Originally Posted by Subie

Please report back when you've done so.

This is all I could find in the BRZ manual.

Fuel types

Unleaded gasoline (93 AKI [Research Octane Number 98] or higher)

If unleaded gasoline with an octane rating of 93 AKI (98 RON) is not avail-
able, unleaded gasoline with an octane rating of 91 AKI (95 RON) may be
used with no detriment to engine durability or driveability.

I don't have a copy of the FRS manual ATM.

Edit: Looks like premium is required, I couldn't find the FRS manual but I did find one of the press releases saying premium was required. Sorry guys, I thought after reading the entry on fuel 6 times I wouldn't get confused on which grade was required.

[DeeezNuuuts83]

But that's understood, since 93 isn't available across the country, as California has 91 as our premium. But it doesn't say anything to going below premium (meaning 87 or 89).

[Subie]

Originally Posted by Allch Chcar

This is all I could find in the BRZ manual.

It also says this on page 420:

Fuel octane rating
This octane rating is the average of the Research Octane and Motor Octane numbers and is commonly referred to as the Anti Knock Index (AKI).
Using a gasoline with a lower octane rating can cause persistent and heavy knocking, which can damage the engine. Do not be concerned if your vehi- cle sometimes knocks lightly when you drive up a hill or when you acceler- ate. Contact your SUBARU dealer if you use a fuel with the specified octane rating and your vehicle knocks heavily or persistently.