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Old Aug 4, 2015, 07:34 PM
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Should I use 87, 89 or 93 octane on my 5.9l?

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Old Dec 8, 2014 | 10:13 PM
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Will it hurt my truck to run 110 OCT.I have a 1997 Ram 1500 with a 5.9L All stock???
 
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Old Dec 8, 2014 | 10:21 PM
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Hurt? Nope. Of course, it won't really help either. The engine is designed to run on regular gas. If you get too much spark knock, and you have the usual suspects fixed, (plenum....) then bumping to 89 will help. 110 is a waste of money.
 
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Old Dec 8, 2014 | 10:44 PM
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Ok thanks
 
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Old Dec 8, 2014 | 11:46 PM
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My 5.9 runs great using 87 octane. When I eventually install a 408 engine, it will also be tuned to run on 87 octane. These trucks get poor fuel mileage anyway, so why pay even more by having to purchase more expensive, higher octane fuel? I'd rather spend my funds in other places besides the gas station.
 
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Old Dec 9, 2014 | 12:24 AM
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I've run a gallon of two of old left over two stroke gas in my truck before and It didn't even care. Hell it might of even ran better.
 
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Old Dec 9, 2014 | 07:41 AM
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I just went through my first tank in my 45K 96 4x4 . It was regular 87 . Truck felt like an old dog to me , I'm use to more get up and go .

I filled up with 91 at Costco as the price is par with reg. everywhere else . It's a 30 mile trip home and I gotta say , she steamed up the hills a lot better with less throttle than before . Hopefully I get more mileage outta this tank , I think I gotta dry u-joint somewhere . Checking that today .

I like my premium gas . I always get better MPG's , better feel and response . Ethanol sux . Both my jeeps have perf tunes so I'm use to paying .
 
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Old Dec 9, 2014 | 07:39 PM
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some of the high octane gas contains lead .... ie aviation fuel which tends to foul plugs, o2 sensors, cat etc. So it could hurt depending on what is in it.
 
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Old Dec 9, 2014 | 11:17 PM
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These trucks are designed to run on 87 octane gas, but the gas that's produced today is such poor quality, especially with the ethanol they add to it. If I run 87 octane gas in my 08 dodge ram or my 2000 dodge ram, they run like crap and have no power. I run only 91 octane gas in both trucks, and there is a huge difference in how the trucks run. There is a very noticeable improvement in power and an improvement in gas mileage.
I would tell you to run 91 octane, its worth it (in my opinion).
 
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Old Dec 9, 2014 | 11:24 PM
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Originally Posted by AtomicDog
My 5.9 runs great using 87 octane. When I eventually install a 408 engine, it will also be tuned to run on 87 octane. These trucks get poor fuel mileage anyway, so why pay even more by having to purchase more expensive, higher octane fuel? I'd rather spend my funds in other places besides the gas station.

Why would you build a 408 and then run it on 87 octane ?, that makes no sense what so ever. Running it on 87 octane gas your going to have to retard the timing so much that you might as well be running a stock engine.
To get the power you are looking for out of the 408 you need to run 91 octane gas at the minimum so you can advance the timing to make more power.
 
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Old Dec 9, 2014 | 11:38 PM
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Originally Posted by Ram Driver
Why would you build a 408 and then run it on 87 octane ?, that makes no sense what so ever. Running it on 87 octane gas your going to have to retard the timing so much that you might as well be running a stock engine.
To get the power you are looking for out of the 408 you need to run 91 octane gas at the minimum so you can advance the timing to make more power.

What you have stated is one man's opinion. The key to building a motor to make decent power is the combination of components and how they are made to work together effectively. The 408 combo that I'm planning will run great on 87 octane fuel.
 
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