What Gas Should I Use - Dodge Dakota Forum

RE: What Gas Should I Use
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well unless its chiped or a mopar pcm you use reg 87 ----91 does nothing for a stock engine if anything you get less mpg with it and it will usually set the mil because it mess's with the 02's

SVTCobraR315
Dodge Dakota
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3/09/2004
23:52:49

RE: What Gas Should I Use
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thanks

uh Chip
Dodge Dakota
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3/10/2004
17:03:31

RE: What Gas Should I Use
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ya got one wrong budd, the 91 octain gas WILL NOT set a code as it does not in any way mess with the O2's. octain only inhibits pre-ignition.

MY H3RO
Dodge Dakota
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3/10/2004
17:14:15

RE: What Gas Should I Use
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If you have no pre-ignition you can use 87. I put $3000 into the engine of my 77 Vette but didn't raise the compression and still use 87. No PING

capone
Dodge Dakota
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3/10/2004
17:31:08

RE: What Gas Should I Use
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I use 92 in my 94' 3.9. I notice a difference. I'm not sure why,
but in my manual it says that higher octane is ok, but in later
models, like my Dad's 98, it says not to use it. Check the book
and it'll tell you whats best.

deerridge
GenIII

3/11/2004
11:37:57

RE: What Gas Should I Use
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Everytime I've checked gas mileage between 87 and 93 octane gases the higher test gets better gas mileage. Usually about 10% and they certainly run better and cleaner. My Dak is the first one truck I've had that you didn't get valve rattle on 87 octane. Probably due to the Overhead cam.

Real Horsepower

Kowalski
Dodge Dakota
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3/11/2004
16:02:13

RE: What Gas Should I Use
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Actually its largely due to the aluminum heads on youur 4.7, the location of the cam really has nothing to do with it.

deeridge
Dodge Dakota
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3/12/2004
14:07:28

RE: What Gas Should I Use
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How would the aluminum heads impact the valve rattle? I was guessing the cams because the push rods were gone. Less stuff, less noise. Hi test does have a definite impact though.

Kowalski
Dodge Dakota
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3/12/2004
16:25:17

RE: What Gas Should I Use
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What you are hearing isn't actually "valve rattle" if it goes away with higher octane - the knocking you hear is detonation -the gas is exploding rather than the smoother burn you want to push the piston down. Higher octane is harder to ignite, so it resists detonation. Aluminum heads are less prone to detonation because they conduct more heat away from the combustion chamber.

deerridge
GenIII

3/12/2004
16:30:02

RE: What Gas Should I Use
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That makes more sense. The higher octane burns more efficiently, hence the results I've seen for over 35 years on every kind of vehicle.

Real Horsepower

.DOC.
Dodge Dakota
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3/12/2004
18:44:08

RE: What Gas Should I Use
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Deeridge,

Kowalski is spot on. The 'efficiency' you're referring to is that the higher the octane, the slower the fuel burns (strangely enough) and hence more power (in an engine that requires that higher level of octane).

Use the lowest octane that will prevent ping/knock. Use of higher octane than that is generaly not cost effective.

Doc

01Motorsport
Dodge Dakota
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3/12/2004
21:26:48

RE: What Gas Should I Use
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You have to experiment with the octane issue. Don't forget that older, high mileage engines begin to require more octane to maintain performance. Sometimes, a few gallons of 92-93 in a tank of 87 will be just enough to prevent pre-ignition.

Real 104
Dodge Dakota
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3/13/2004
08:56:30

RE: What Gas Should I Use
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Kowalski, you are 95 % correct. Detonation is also called pre-ignition. Usually it is caused by a couple of factors, either together or seperately. One is the timing is too far advanced and the plug is firing too far before TDC, in this case higher octane is not going to help. The other is hot spots caused by either sharp edges within the combustion chamber that get hot or carbon deposits that can glow and ignite the fuel before the plug fires. In a low po engine too high of an octane can lead to carbon deposits. In both of these examples the igniteing of the fuel is attempting to push the piston down before it has reached the top of its stroke. This is where the rattle comes from.

You are compleatly correct on the alum. head issue. use the lowest octane to avoid detonation under load and yo can save some money at the same time.

Real 104
Dodge Dakota
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3/13/2004
08:56:55

6lizrd
Dodge Dakota
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3/13/2004
23:38:36

RE: What Gas Should I Use
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thanks guys for another good topic, i've learned something here again. on a related subject i was wondering what BRAND of gas you all buy ? i try to buy Phillips 66. what would be another good choice from an American company ?

AmsoilSponsor
DakotaEnthusiast

3/14/2004
11:25:37

Amsoil Synthetics, What Gas Should I Use? Octane?
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What gas should you use? Regular, Plus or Premium ?

Run what your owners mauual specifies. Put the high-octane in an engine designed for 87 and you have incomplete combustion ... and a waste of 20 cents per gallon.

Most production street vehicles, even high performance ones, are not going to benefit from anything higher than the recommended octane. So it only really becomes an issue if you are unfortunate enough to live in a state that has made unavailable the octane your engine was intended to burn (like California).

Octane rating is a measure of the fuel's resistance to pre-ignition. High-octane is specified by manufacturers when the engine requires it. High compression, high temps, or turbo engines will do better with high octane due to its slower burn rate.

Basically, the numbers you see at the pumps only indicate the anti-knock index of the fuel. It is measured using RON + MON and the divided by 2 (R+M)/2. In short, RON (Research Octane Number) measures the fuel's anti-knock index simulating light load, typical street, normal driving conditions. MON (Motor Octane Number) measures the fuel's anti-knock index simulating high-speed, high load conditions.

They used to post the RON and MON octane numbers in small print on the Sunoco pumps but I haven't noticed this lately.
__________________________________________________

TOO MUCH OCTANE CAN BE BAD

Right now there is a lot of talk about the highest octane fuel that you can make (or used), especially in the "street racing" fuel business. People relate the highest octane to "my motor is making more power". That is simply not the truth.

One of the downsides to building (or using) a fuel with ultra-high octane is that the blend really slows down the flame front in the combustion process. You can get the flame front so slow, that the engine is now running in a "too-rich" condition. This actually takes away horsepower. Bottom Line --- you are slowing down the flame front and getting rid of detonation, at the expense of losing horsepower.

I hear of this all the time from my clients that "street race" --- engines running "heavy" ... and they are trying to tune it to lean it out, when actually the flame front is causing the problem.
__________________________________________________

Request a FREE Amsoil Catalog by clicking the following link:

Steven Roark , Amsoil Dealer , Proud Sponsor of www.DodgeDakotas.com

AMSOIL Synthetic Motor Oils, Lubricants, Filtration, and Truck Care Products

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