I was looking into the jet chip and it reccomends 91-93 octane fuel but the owners manual for the truck doesnt reccomend higher than 87. would there be any harm on the engine if I were to run a tank of 89 or 91?

 

If you plan to run a higher octane on a stock motor, there is no harm but also there is no gain. I say don't run it unless you need it. There was an article a long time ago in Sport Compact Car Magazine where they got a V6 Accord and ran 91 octane through it when it only need 87. They threw it on the dyno and the car lost 10hp when they ran 91 octane.

 

Unless your motor is tuned to take advantage of the higher octane, you're wasting time and money.

 

I saw a guy at the station I work at put 87 in his Viper.

 

WoW

I stupid bro put 87 in his Banshee and then asks why it bogs. I told him that 2-stroke needs high octane and now he runs 110 in it. Gotta love that smell!

 

If you use a chip that requires 91 or 93 octane, you will need to use that higher octane to get the performance it was designed for. In fact you may possibly harm the engine if you use lower octane fuel when the chip is set for higher octane. The 4.0 SOHC engine is suppose to have a detonation sensor that retards the timing but it has a limit as to how much it will retard.

I have run my Ranger on an 91 octane progam and used 89 octane with no probelms but Doug at Bama recommended I not do that. He said it could create long term problems.

The owner's manual states that you should run only 87 octane because that is what it is tuned for. When you install a chip, you have just changed the tuning of the truck and should use what it calls for.

 

ahh, thank you for the info

 

well. i've been running 89 on my 94. mostly cuz its cheaper than 87 cuz here i iowa, we think we need to add 10% ethanol to the mix.

 

Not a fan of ethanol. It's efficient burn ratio is around 9:1 (9 parts oxygen 1 part fuel), where as methanol is 14.7:1. Most newer cars oxygen sensors will pick this up and start throwing more fuel into the engine and decreasing the gas mileage that you get. Although it isn't bad to run sometimes because it does clean the tank out a bit it seems (But it still uses a mixture that can be bad for seals, normally only in older cars though). I am, however, a fan of E85 if you're set up for it, but that's for different reasons.

As far as my opinion on the OPs topic. I always put higher octane in my gas engines before I go tow anything of a decent weight simply because even though it may be a hp/tq loss, you figure you're putting more stress on the engine anyway, causing it to heat up more. When this happens, you will be more prone to detonation and a higher octane rating could help save your internals in this case. All higher octane is, is a slower, more controlled burn which is why higher compression and higher power trucks/cars use it. It's less likely to ignite prematurely (which is what detonation is, there is another form of detonation but we wont get into that).
However, as far as daily driving and normal highway driving, I always recommend the lowest octane that your engine can handle for peak power and mileage. So higher octane will by no means hurt your engine, but if you use it correctly, it can really help. Just remember, the lower the octane, the faster the burn, the more power you get as long as you're avoiding detonation.

If you wanna know a little trick I use when I'm on the road, if you ever encounter detonation due to bad fuel, I would recommend staying away from the "octane boosters" in auto stores, head to a chemical or paint store and pick up either Toulene or Xylene. Toulene is rated at 114 octane and Xylene is rated at 117.
Here's the breakdown if you mix with Toulene.
Mixtures with 92 Octane Premium
10%...94.2 Octane
20%...96.4 Octane
30%...98.6 Octane

Which is decent compared to the "boosters" you get at the auto store which are normally rated for 2-3 points (so those only increase your octane to about 92.3 total, per $5 bottle when you can buy a gallon of Toulene for around $3 a gallon!).

But anyway, if you're interested in that stuff here's a link.
http://www.gnttype.org/techarea/misc/octanebooster.html

 

and the tuners chips and whatnot just use that slower burn to....? I'm kinda new to this octane/chip thing.

 

Simple breakdown:

Higher octane decreases the likely-hood of detonation, advanced ignition timing (what a lot chips do in a nutshell) increases the likely-hood of detonation at lower octane levels, but increase power and fuel economy. Normally if you have a chip, you're going to need to run higher octane fuel.

Also, if anybody feels I'm a little off in my information, please feel free to correct me. I'm only human here and I'm going to learn up until the day I die.