Best Gas in Alberta
06-17-09, 10:19 PM
#1
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Best Gas in Alberta
Hey guys just wondering where do you fill you car up in your boosted engines? Why?
I fill up @ Husky for the 94 Octane. Not sure if its the best, but definitely the highest octane i can buy.
-Mark
I fill up @ Husky for the 94 Octane. Not sure if its the best, but definitely the highest octane i can buy.
-Mark
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06-19-09, 07:09 PM
#9
I get way better milage when I run Shell. But for some reason in rotaries, it runs like ****, so Esso is the way to fly.
Husky was the worst fuel on milage I've ever used. I get 230 more kms out of a tank in my rover running Shell 91. And it runs better too boot.
Husky was the worst fuel on milage I've ever used. I get 230 more kms out of a tank in my rover running Shell 91. And it runs better too boot.
06-20-09, 10:34 PM
#11
i was reading a big article on why that is, and it has partly to do with the chemical makeup of lower octane fuels. I'll see if i can find it around, i first read it on srtforums.com when i was an active member there. Bascially that lower octane pump gas is more unstable and prone to detonation partly because there is more potential energy due to a slightly different arrangement of the molecular bonds. Higher octane fuels are more stable but contain less potential energy because the hydrocarbon chains are different. Ethanol boosts the octane rating by making the fuel more stable, but it contains less energy. Something to that effect anyway. If there are any experts on the subject, feel free to chime in. I won't be offended
06-22-09, 01:21 PM
#12
^^You basically have it right. Lower octane gas is more prone to compression ignition - in other words, detonation/knock. As typically formulated, it actually has slightly higher chemical-potential energy content/litre. Higher octane fuel is by definition more resistant to knock - traditionally, this meant the fuel had a higher proportion of octane relative to the easier to ignite heptane, but now it just refers to how the fuel behaves in standardized testing for knock resistance. The reality is pump gas is a mix of many different hydrocarbons as well as specialized and proprietary additives, some for fuel system and upper engine cleaning, some for increasing octane ratings. Pumps display an octane number that is the blend of two different rating systems (Research Octane Number, or RON, and Motor Octane Number, MON).
Boosted engines and high-compression engines are more likely to need high octane rated fuel to resist pre-ignition (detonation) of the mix in the chamber/cylinder due to high pressure and temperature - the higher the boost, and-or compression, the higher the octane rating of the fuel needed to resist detonation. Most turbos incorporate a knock sensor to retard timing and-or limit boost if detonation is detected. So do many "higher end" or high compression n/a cars. The presence of a knock sensor may allow turbo or n/a cars to take more advantage of available knock resistance in the fuel to advance spark and, for forced-induction cars, boost beyond what ambient temps and air conditions might otherwise allow, allowing the engine to make better use of the fuel for power or efficiency. It may also allow a car intended for premium gas run on regular, at the cost of reduced performance/mileage.
For most un-modded cars, higher octane fuel than the manufacturer calls for contributes nothing except lightening your wallet.
As far as better or worse gas, it may vary by the car and state of tune/maintenance. Ethanol has lower energy content (about 2/3), compared to conventional gas, so for many cars they will get lower mileage on ethanol-blended fuels. On the other hand, ethanol has much higher knock resistance, so for some cars running high boost or compression, or an older car that may have deposit buildups (which can increase compression and create hot-spots on the piston, valves, and combustion chamber, or on the rotor face of a rotary), the higher knock resistance may allow them to run higher boost or avoid spark retardation to prevent knock, and they may get higher mileage by taking advantage of the increased knock resistance.
Boosted engines and high-compression engines are more likely to need high octane rated fuel to resist pre-ignition (detonation) of the mix in the chamber/cylinder due to high pressure and temperature - the higher the boost, and-or compression, the higher the octane rating of the fuel needed to resist detonation. Most turbos incorporate a knock sensor to retard timing and-or limit boost if detonation is detected. So do many "higher end" or high compression n/a cars. The presence of a knock sensor may allow turbo or n/a cars to take more advantage of available knock resistance in the fuel to advance spark and, for forced-induction cars, boost beyond what ambient temps and air conditions might otherwise allow, allowing the engine to make better use of the fuel for power or efficiency. It may also allow a car intended for premium gas run on regular, at the cost of reduced performance/mileage.
For most un-modded cars, higher octane fuel than the manufacturer calls for contributes nothing except lightening your wallet.
As far as better or worse gas, it may vary by the car and state of tune/maintenance. Ethanol has lower energy content (about 2/3), compared to conventional gas, so for many cars they will get lower mileage on ethanol-blended fuels. On the other hand, ethanol has much higher knock resistance, so for some cars running high boost or compression, or an older car that may have deposit buildups (which can increase compression and create hot-spots on the piston, valves, and combustion chamber, or on the rotor face of a rotary), the higher knock resistance may allow them to run higher boost or avoid spark retardation to prevent knock, and they may get higher mileage by taking advantage of the increased knock resistance.
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