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Author Topic: premium unleaded vs regular Back to Topics
Rookie Author

Joined:Dec 2012
Message Posted: Nov 30, 2013 12:13:54 PM

will premium raise my fuel economy at all to compensate for the higher price? Also, is there anything good about it versus regular ?
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All-Star Author Indiana

Joined:Apr 2012
Message Posted: Dec 6, 2013 2:23:53 PM

If your manufacturer recommends 87 octane (regular), then the engine's state of tune, oxygen sensors, the mapping in the ECU are all optimized for regular. Complaints among friends who have used 89 instead of 87 have ranged from rough cold starts, excessive engine noise to destroyed water pump. I am not saying all this will happen in your car, but in the long run, it is better to stick to manufacturers recommendations, not just on octane rating, but oil, transmission fluid, tire pressures and a myriad of other variables.
Rookie Author Ottawa

Joined:Aug 2002
Message Posted: Dec 4, 2013 9:46:18 PM

For turbo engines, Premium even 94 Octane is recommended for fast performance & take-off, Regular risks engine damage, my Subaru tuners assure me.
Champion Author Atlanta

Joined:Sep 2003
Message Posted: Dec 3, 2013 11:47:13 AM

Reality: 1) Premium is intended to prevent pre-ignition in high compression engines; 2) The engine must be able to advance or retard the spark in response to the fuel octane.

Most cars, however, are designed to run regular and no benefit is derived from using premium unless the car is knocking/pinging. The 2005 Buick Century is almost certainly in this category.

Some late model cars have the ability to use any octane fuel. In such cars, using premium does yield an advantage but that advantage in fuel mileage is unlikely to be equal to the price spread between regular and premium which in most areas is between 30 and 40 cents.

It is far better to learn to drive efficiently than it is to use premium to increase fuel mileage.

[Edited by: Houckster at 12/3/2013 11:47:47 AM EST]
Champion Author Fort Worth

Joined:Mar 2011
Message Posted: Dec 2, 2013 8:21:07 AM

Wrong question. Only run premium fuel if it is absolutely required.
Champion Author South Dakota

Joined:Mar 2005
Message Posted: Dec 2, 2013 8:18:18 AM

It is usually a wash. You might gain enough mileage to cover the additional cost.
Champion Author Lexington

Joined:May 2005
Message Posted: Dec 1, 2013 8:31:32 AM

You positively will not get better mileage and the higher octane can clog and dirty up your intakes if the car is designed to run on 87 octane gas.
Champion Author Pennsylvania

Joined:Jun 2003
Message Posted: Dec 1, 2013 8:02:18 AM

Rookie Author Omaha

Joined:Dec 2012
Message Posted: Dec 1, 2013 12:06:42 AM

also thank you for the explanation.
Rookie Author Omaha

Joined:Dec 2012
Message Posted: Dec 1, 2013 12:06:02 AM

hello thank you for the tips I have a 05 buick century it has a 3.1 v6 the owners manual just says 87 minimum or higher octane. DO you think there would be any benefit then for a like midgrade 89 octane? thanks Mike
Champion Author Maryland

Joined:Aug 2004
Message Posted: Nov 30, 2013 8:36:27 PM

"will premium raise my fuel economy at all to compensate for the higher price?"

No. For that matter, premium won't raise your fuel economy at all, let alone to compensate for any price increase.

" there anything good about it versus regular ?"

Yes, but it takes a little explanation.

First, and most important, you haven't told us what your car manufacturer requires or recommends for your specific car. (Or, for that matter, any particular car you want to discuss.) So, not knowing the specific vehicle you're talking about, in a high-compression engine that's designed to run on premium fuel, premium will provide some additional power. But, if you want to save some money, you can probably still fill up with regular, unleaded fuel much of the time.

However, if your vehicle calls for using premium gas instead of regular, it's because your manufacturer decided to use what's known as a "high compression" engine. An engine with a high compression ratio has some advantages. It squeezes more power of the same-size engine. But, it requires you to spend more for every tank of gas, to get that extra power. In other words, instead of manufacturing a car with a larger, but lower-compression-ratio engine, manufacturers are using high compression engines, and foisting the additional cost back to you - by forcing you to buy premium gas to get that extra performance.

Again, because you haven't said if premium is required or recommended for your specific vehicle, if you use regular instead of premium, you might get engine pinging or knocking. (Pinging or knocking are noises, which are signs that the gas and air mixture in your car's cylinders isn't burning exactly as intended. The sound you hear is the result of the fuel and air mixture combusting unevenly in the cylinder. Pinging or knocking will reduce the efficiency of your engine and, over a very long period of time, it can cause damage.

In a normally operating engine, the spark from the spark plug ignites the mixture of fuel and air, causing an extremely rapid burning of the fuel in the cylinder. That's good. It's what creates the pressure that makes the piston travel down very fast, causing the crankshaft, your transmission, and ultimately the wheels to turn. Illustration #3 However, it's possible for the mixture of gas and air to burn somewhere else in the cylinder, simply from the pressure (or compression) within the cylinder, and not from the spark. That's called "pre-ignition," and it's more likely in a high-compression engine. When the fire you want (that's the one from the spark plug), collides with the fire you don't want (that's the one resulting from the pre-ignition), the result is a ping or, if the pre-ignition fire is big enough, a knock. The degree of severity, including the amount of noise generated, is determined by how big that unwanted flame is.

Compared to regular gas, high-octane gas requires higher temperature and pressure to ignite, so it can withstand higher compression without reigniting. As such, it's less likely to result in premature ignition, and therefore prevents pinging and/or knocking.

In other words, it's a form of protection for high compression engines.

Does that answer your questions?
Champion Author Lexington

Joined:Jun 2013
Message Posted: Nov 30, 2013 2:00:48 PM

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