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Old 04-16-2011, 10:03 PM
 
Location: Los Angeles
4,765 posts, read 6,924,903 times
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I have a 2002 Dakota R/T with a 5.9 V8, and my owner's manual says regular gas.
I have been using regular all the time, and it runs excellent.
Bob.
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Old 04-16-2011, 10:17 PM
 
809 posts, read 893,935 times
Reputation: 991
Some cars require the higher octane to run properly. For example most Honda's that run higher compression (like the s2000, SI's etc) won't engage vtec and will stay on the small cam, regardless of RPM's. As for all gas being the same octane, sounds like 100% urban legend BS.
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Old 04-16-2011, 11:01 PM
 
4,248 posts, read 10,228,903 times
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Quote:
Originally Posted by Coldjensens View Post
However my question is whether there is really any difference. According to my friend, it is all higher octane. IN other words, if you buy 87 octane, you are getting 91 octane, if you buy 89 octane, yu are getting 91 octane, and if you buy 91 octane, you are getting 91 octane. He claims it is cheaper for them to jsut sell higher octane to everyone than to seperate the gasoline. The ratings are just used to charge some people more. Is this true? Anyone know?
Your friend is an idiot, sorry. You think a store bought 91 octane at a higher price to sell it as 87?

91 is more per gallon than 87 for the store owner to the consumer. The owner of the store gets charged more for premium than regular and recoups it by (you guessed it) charging the consumer more for mid grade and premium. And fyi, most stores don't have a mid grade tank. It actually takes 2/3 of 87 and 1/3 of premium to make an 89 octane blend. If you want to see for yourself. Next time you fill up pick mid grade. As you're filling up watch the counter on the premium and watch it count up as you're filling up.


I work at a pipeline which has a refined fuel rack so I'm not talking out my butt like your friend.

Last edited by piyf; 04-16-2011 at 11:09 PM..
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Old 04-16-2011, 11:02 PM
 
Location: un peu près de Chicago
773 posts, read 2,001,637 times
Reputation: 515
Knock sensors detect knock and retard ignition to a point just below knock. An engine requiring high octane will run on lower octane, but the spark will be retarded and the engine will have less zip.

Higher octane also has slightly higher energy density than regular. For the nonpareil in energy density, try aviation fuel.
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Old 04-17-2011, 10:15 AM
 
4,248 posts, read 10,228,903 times
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Quote:
Originally Posted by Zea mays View Post
Knock sensors detect knock and retard ignition to a point just below knock. An engine requiring high octane will run on lower octane, but the spark will be retarded and the engine will have less zip.

Higher octane also has slightly higher energy density than regular. For the nonpareil in energy density, try aviation fuel.
Try it and say bye bye to O2 sensors and your cats.

A cheaper and safer alternative is E85, 106 octane.
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Old 04-17-2011, 10:56 AM
 
Location: WA
5,293 posts, read 20,701,286 times
Reputation: 5622
Quote:
Originally Posted by danieloneil01 View Post
Try it and say bye bye to O2 sensors and your cats.

A cheaper and safer alternative is E85, 106 octane.
E85 is only an option for Flex Fuel vehicles and in my experience it costs more to use as the lower price does not make up for lower energy content... you wind up with much lower MPG and therefore limited range.
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Old 04-17-2011, 11:14 AM
 
48,519 posts, read 81,013,914 times
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Consumer reports got a average of 27% less mial;ge per tank on E85 in the same flex fuel vehicles in their testing. Even the producers acknowledge less but say it averages 20% less.
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Old 04-17-2011, 12:01 PM
 
8,317 posts, read 25,095,377 times
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Altitude affects the octane calculation. For example, almost all regular fuel sold in Colorado (which is all above 3,300 feet elevation) is 85 octane. It is THE EXACT SAME FUEL that is rated 87 octane at lower elevations--and an engine that requires 87 octane at sea level will run just fine on the 85 octane sold in Colorado.

Using premium fuel in an engine that does not require it is just a waste of money.
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Old 04-17-2011, 02:13 PM
 
10,713 posts, read 11,412,857 times
Reputation: 4751
Nearly all cars are designed to run just fine on 87 octane and buying the more expensive, higher octane gas for the most part is just wasting money. The only cars that usually require premium are performance, luxury, have a turbo/supercharger or heavy duty trucks.
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Old 04-17-2011, 10:19 PM
 
4,248 posts, read 10,228,903 times
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Quote:
Originally Posted by cdelena View Post
E85 is only an option for Flex Fuel vehicles and in my experience it costs more to use as the lower price does not make up for lower energy content... you wind up with much lower MPG and therefore limited range.
Huh? I quoted someone else unrelated to what you're talking about. I'm aware of what you said in your post already.
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