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Jecht
Dodge Dakota
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11/20/2005
17:05:05
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 Subject: RE: Premium or 87?
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I know the book calls for 87 in my 4.7 but it seems to run like crap. so when I run 89 my truck seems to run smoother and preform better. but with 91.My truck just drinks this like a drunk with a case of beer. so I run 89 with no prob.
N56629 I wouldnt run the 93 program with 89 gas. people had said it will make your truck run like crap. 93 program is only for 93 gas. you have to remember depending on where yo u live. they change the formula of the gas in the winter and causes your gas mileage to go down.
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N56629
Dodge Dakota
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11/20/2005
19:57:57
| RE: Premium or 87?
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The only way I will know is run the program for at least one tank. I'm thinking that they have already introduced winter formulation here. My mileage dropped from 18+ to about 16.5-17 and will probably get worse as it starts to stay in closed loop longer.
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jpkomm
Dodge Dakota
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12/01/2005
14:13:34
| RE: Premium or 87?
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I think what it boils down to in the end is that each vehicle is different. Even same-year same-model vehicles will not run smoothly on the same fuel grade. Fuel brands/quality does play a part to be for sure. My best opinion is to find a brand you like (I like BP for instance) and if your vehicle runs smoothly on 87 oct.. then fine, dandy, leave it at that. You aren't really going to get much of a mpg improvement to really rejoice about on a V8 Dak anyways. Just go with what your vehicle enjoys and what your truck's computer won't go hari-kari on.
In my previous experience, non-stock vehicles sometimes require more octane than stock vehicles. I had a 97 Gr Cherokee with a 5.2L modded engine. It would not run on 87 octane (ping, knock, surging, etc). However, my 00 Dak with the 4.7L runs smooth on 87 Octane.
Some vehicles cannot be run with 93 octane because it can burn too hot and potentially damage your engine. This happened to a friend who swore by 93 octane in his 95 Ranger 2.3L and ended up burning up his engine (pistons or valves I believe.. been a while so I don't quite remember). Vehicles like the 04 Toyota Tacoma I had, it said it is designed to run at 87 but for "optimal performance" you can use up to 93 octane.
And the great gas mystery marches on...
Just my 2 cents, take it or leave it. :)
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Kowalski
GenIII
12/01/2005
16:46:33
| RE: Premium or 87?
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Most vehicles that say to run higher octane for higher performance have knock sensors that retard timing with lower octane - no mystery there. There's no doubt a vehicle modded for higher compression or more spark advance may require higher octane.
If I were N....., I'd try the lower octane too to see how it runs - after all, he can always change the program back if it pings. The custom flash I got recomended premium, but I've found the only time I need it is towing a good load - otherwise it runs great on 87 (just as someone on this site told me it worked for him). Only one way to find out...
93 is harder to ignite than 87, but I don't think it burns much hottter. I'll bet the blame for that guy's damage belongs elsewhere.
Lead, follow, or get out of the way
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jpkomm
Dodge Dakota
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12/01/2005
18:19:02
| RE: Premium or 87?
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Kowalski--
Good points! Yeah, it is possible the problem with my friend's vehicle originated elsewhere. Thats what the shop told him though when they tore apart the engine. However, I am a firm believer in that there is never "just one problem". It is always a bunch of smaller problems that pile into one big problem. ;)
I am wondering about something I read about higher-octane fuels though (like 93 octane or thereabouts).. I read that it tends to leave more residue and doesn't always totally burn if your engine is rated for 87 octane. Think I got that off of About.com. Any truth to that? Of course that really doesn't go in-line with the "burning hotter" bit that mechanic told me, but it seems that different people have different opinions on high octanes. And, in different perspectives, they all make dang good sense in their own right. Hehe
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Kowalski
GenIII
12/02/2005
16:30:40
| RE: Premium or 87?
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Well, might leave more deposits since higher octanes resist knocking by being harder to ignite - slower flame front. Chemists seem to claim there is the same amount of energy in the different octanes, so that's why I question it burning much hotter. I've heard some people use higher octane because they say there is more detergent in the higher grades, not sure if that's true or not. I've always run regular when I can; and its never caused me any trouble.
Lead, follow, or get out of the way
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GraphiteDak
GenIII
12/02/2005
18:01:04
| RE: Premium or 87?
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As far as I always understood, higher octane just has a higher flash point or whatever (resistance to combustion). It's not MORE flammable, that's for sure! It doesn't make MORE POWER either. High compression engines (or boosted) need the higher octane to resist PRE ignition. Colder plugs help too.
That's something I'd like to someday try on my Dak. Colder plugs. Then try the performance/towing programs again.
I also think the more expensive/higher octane fuels have more detergents. That's why it's PREMIUM or SUPER grade vs. the 87 grade.
It was nice when they came out with the middle grade.
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