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JerryM
Dodge Dakota
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3/14/2007
09:47:43
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 Subject: 87 or 89 octane??
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Message:
I know this has been posted before, but just to get some new ideas.
I run 87 octane in my 2000 4.7 liter V8, which runs fine but only averages 14-15 MPG driving around town.
I have been told going to 89 octane will improve your gas mileage by the dude at the auto parts store.
I personally did not think so but wanted some opinions, advice, or even just the facts.
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dude
Dodge Dakota
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3/14/2007
10:59:45
| RE: 87 or 89 octane??
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the dude at the auto parts store was selling fries & burgers 6 months ago..
in some cases, engines equipped with a knock sensor the computer advances timing until pre-ignition is detected, so with 89 octane more timing advance is possible, and sometimes a MPG gain.
pretty sure the 2000 4.7l doesnt have a knock sensor,
if so there is really no gain in running a higher octane than necessary, try running a slow burning 110 octane race gas, it might still be combusting by the time the exhaust valve opens and your manifolds would glow red.
low octane = fast burning, may ping or pre-ignite in some conditions, carbon build-up, high engine load.
high octane = slow burning to resist pre-ignition in high compression engines, useless if engine/mods dont require it.
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Kowalski
GenIII
3/14/2007
16:15:58
|  RE: 87 or 89 octane??
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Message:
Yup, only the HO version of the 4.7 gets knock sensors. Mine gets the same milage on higher octane, just run the 87.
Did the guy ask if you wanted fries with whatever you got ?
Lead, follow, or get out of the way
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OBIO3
Dodge Dakota
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3/14/2007
21:47:19
| RE: 87 or 89 octane??
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Also the higher the octane the slower the burn. The real reason higher octane can help with spark knock. Not a fix at all . just a bandage.
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sneilan
Dodge Dakota
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3/16/2007
06:44:16
| RE: 87 or 89 octane??
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Message:
i know that by all accounts the octane of yourgas should makeno differance in your mpg, but i swear that if i run premium gas in the winter, i get 50-70 more miles per tank than when i run regular. now this is only in the winter, in the summer i get the same mpg regardless of the octane, usually around 300 miles per tank.
Sean
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Kowalski
GenIII
3/16/2007
06:56:44
| RE: 87 or 89 octane??
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Miles per tank can be a very deceptive way to figure milage - you're better off figuring miles per gallon.
Lead, follow, or get out of the way
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Florida Boy
Dodge Dakota
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3/16/2007
07:19:09
| RE: 87 or 89 octane??
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I pull a 25 foot airstream (That is set up right for towing) with my 02..4.7liter 4X4, 5 speed stick. When useing 87 octane I spend a lot of time in 4th gear and on long trips have the engine light come on. This condition clears up with a can of fuel additive and 89 octane. I also can pull a lot more time in 5th gear, and more power. 100000 miles on my truck. no modifications to date. new O2 sensor in order and Jet chip next purchase.
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Kowalski
GenIII
3/16/2007
11:30:02
| RE: 87 or 89 octane??
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Message:
Why the jet chip ? I have a custom flash myself, but most of the guys who went with a chip seem to favor superchips - and don't say much good about the jet. It's normal to pull better with high octane when towing a heavy load, if you have the ignition advance to justify it; but I didn't think that's what the original poster was asking about. I run premium to be safe when towing with the advance I run, but 87 works as well the rest of the time.
Lead, follow, or get out of the way
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ruff382
Dodge Dakota
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3/17/2007
00:36:30
| RE: 87 or 89 octane??
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Message:
y u b ask dat
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kj
Dodge Dakota
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3/23/2007
15:43:33
| RE: 87 or 89 octane??
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Message:
From personal experience, the truck won't run as good on 89 as it does on 87. Everybodys' fuel mileage sucks on regular but that is what the engine was designed to run on. You can even check your owners manual to confirm that it will run worse on higher octane.
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4.7onN20
Dodge Dakota
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3/25/2007
00:40:52
| RE: 87 or 89 octane??
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Message:
Depends on condition of engine, tune, and compression.
87=fast burning 110= slow burning. if your timing is set to
close to top dead center then 110 would start the main part of
the combustion past the optimum position in the power stroke.
You would just have to test to see where your praticular engine
runs best. I run 93 because I run alot of nitrous which makes
high octane burn faster and preignition is a bitch. I do get worse
mileage off of it though. Dude has a pretty good explination but
I have never heared of extra carbon build up due to using low
octane.
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dude
Dodge Dakota
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3/25/2007
01:12:08
| RE: 87 or 89 octane??
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Message:
I ment 87 is more prone to ping in cases of high engine load or when carbon build-up or hot-spots are present in the combustion chambers.
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N56629
Dodge Dakota
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3/25/2007
07:14:44
| RE: 87 or 89 octane??
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Message:
Try it, it won't cost you anything. During the winter I get better mileage with 89 octane. It's quite possible a different brand could give the same results. There is more to gas than just the octane rating. What they use to get that rating can affect your gas mileage. This is especially true during the winter months.
On my last tank of gas I picked up almost two miles per gallon over the previous tank. It's not uncommon to have your mileage bounce around this time of year as you get winter gas one place and summer gas at another. This usually lasts for only one or two weeks.
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4.7onN20
Dodge Dakota
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3/26/2007
15:26:04
| RE: 87 or 89 octane??
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Oh I see. I just read it wrong. Thats what I get for posting at 1:00 in the morning.
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loser
Dodge Dakota
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3/27/2007
16:27:49
| RE: 87 or 89 octane??
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Hey a minute!
I now work at an auto parts store, 6 months ago I WAS Not making fries and burgers.
I had a good job delivering portable "johnny on the spot" toilets.
So there!
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jayb
Dodge Dakota
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3/28/2007
11:47:58
| RE: 87 or 89 octane??
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Message:
sounds like a pretty successful career to me..
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lmao
Dodge Dakota
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3/28/2007
20:12:51
|  RE: 87 or 89 octane??
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Message:
sounds like a load of Sh!t to me! LOL
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KotaR/T
Dodge Dakota
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4/11/2007
04:21:23
| RE: 87 or 89 octane??
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Message:
octane is a fuel volatility rating. the fuel molecules of lower octane fuel have tendancies to combust at lower combustion temperatures and a lower rate of compression than higher octane fuel. magnum V8's or relatively low compression engines, which means high octane fuel is not needed. and if anybody read their owners manuals, you would discover that DC recommends the use of 87 octane fuel.
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Todd
Dodge Dakota
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4/11/2007
04:35:38
| RE: 87 or 89 octane??
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Message:
Even with the little bump in fuel mileage the price difference makes it all equal out in the end. I have noticed that depending on what brand I buy does make a difference. Chevron and Shell stations seem to be good over here on the east coast
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