Silly me for thinking Ford would leave it in the same place, sorry.

RangerPilot - Yea, let us know if you find it. I want to say it was some time last year, and the subject might have also been related to fuel grades.

 

Combustion chamber carbon deposits can raise the engines compression ratio & cause it to want a higher octane.

Our 4.0L was designed, programmed & timed to operate on 87 octane.

Using a higher octane fuel, without compensating the engines valve & spark timing, is like retarding the timing on an engine. Thus because the premium fuels flame front is slower, if at least the spark timing isn't advanced. the exhaust valve will be opening while the fuel is still burning & that can cook the exhaust valves & the unburned fuel can cause extra carbon deposits.

The cat converter also has to process the unburned fuel, causing it to run hotter!!!!

So unless you have combustion chamber deposit problems, that have raised your compression ratio & octane requirements, or have otherwise messed with the engines timing, there isn't any need or advantage to using premium fuel in these engines.

If your 4.0L needs premium to run right, consider giving it a good decarbon treatment & save some cash.

 

yea pawpaw,, ,i had kinda bbeenn wonndering if mmaybe my high-mileage truck was wanting higher octane due to carbon deposits. i been thinking latley that now may be the right time to do the de-carbon treatment... i've read that post over in the faq section.

Only thing is, Im afraid i'll hurt the poor thing somehow... understand that this truck is my primary vehicle... hell, its my only vehichle. So i cannot afford to have it parked.

if you guys can convince mme that i wont blow it up (lol) i'll give it a shot. just need some reassurance!

this truck is 14 years old (1993) and 150k of its 200k miles were put on it within the past 5 years... mostly on the highway. dunno if that means anything or not for this decarbon thing... but i thought i'd throw that in there.

 

If your talking about the Ford decarbon TSB that uses 3 cans of Motorcraft PM-3 carb cleaner, to clean er up, I've had this done by the Dealer, under warranty.

It didn't last long for me, until my CCDI was back.
Cowboybillyninemile had good luck with the TSB proceedure on his old 94 Ranger 4.0L though.

I get lasting results of keeping my CCDI at bay, by using Chevron or Texaco gas, with a proper 20oz size dose of "Techron Concentrate Plus" in the treated tank of gas & running most of that out, with the "spirited driving" part of the TSB thrown in.

Now doing it this way takes a little longer, you don't get the immediate same day results of the TSB, cause you have to wait until you've usd up the tank of treated fuel, but I like it better, beacuse it removes the deposits gradually over time, like they were built up & it doesn't require the spark plugs, oil & filter, be changed like the TSB does & I get longer lasting results.

Seeing as how most of your mileage has been highway & if it isn't using any oil, the engine should be blown out & fairly clean inside, so a good decarb should be reasonably safe.

If you decide to use the TSB proceedure, DON'T let it inhale so much PM-3 at once, that it stalls & hydrolocks the engine & bends something up!!!

Use something like a sports needle, (the kind used to inflate basket & foot *****) attached to a small dia piece of tubing, the other end attached to a throttle body vacuum port, & the needle end dipped into the PM-3, so it gets it slowly & doesn't hydrolock the engine.

Seeing as how this is your only ride & you can't screw it up, maybe the Techron Concentrate Plus treatment is the safest way to go.

On Edit: Advance Auto has the Techron on a buy one, get one special!!!!

Just some more thoughts to ponder.

 

good stuff pawapw. My daily fill up spot is a Shell station, since its right next to where I live. I understand that Shell has high amounts of detergents in their fuel... so maybe I am doing well using that gas?

Tonight I bought a bottle of STP Super Concentrated Fuel Injector Cleaner (at the same gas station) and tossed that in the tank. I read on the back of the bottle that carbon buildup can cause hard starts, rough idle, and acceleration loss. All of which I am experiencing on a small scale...

The TSB method scares the shnikes out of me to be honest, so I doubt I'll be doing that one. Also, this truck does eat a little bit of oil... but that might just be because I use a full synthetic in my old truck. It holds all its oil till about 3k miles, and then I'll notice that it starts to lose some oil. But like I say, that could just be because I am using a thin, seepy oil on an old truck with OEM seals.

 

Shell is probably one of the better higher octanes on the market right now. Mobil premium is good too.