Tune and Premium Fuel

[HARDTRAILZ]

I know that running premium fuel is pointless with the stock 4.2, but if I am having the pcmforless tune redone, is there an advantage toward using premium fuel? I do not use it currently, but considered specifying that I was going to when I send it in for a reflash. Is there gains to be had? I am not worried about the cost difference.

Random thoughts...

I see that premium gas seems to have less ethanol at higher octanes...I do not like ethanol in my fuel since it hurts performance and mpg.

I have higher mileage.

Premuim burns hotter, may help keep motor cleaner.


Anyone out there that can help me out with this decision?

 

[ConeKilrAutoX]

i too would have liked to have known? I am going to have to be on 93 octane with my turbo install in the spring, but thats strictly due to the forced induction and spark and timing ..etc. I have used 89 prem on my pcm4less tune and i see no difference vs the regular 87 i used to before except slightly better millage on the highway and slightly more power. I have 150,xxx

 

[Wooluf1952]

i too would have liked to have known? I am going to have to be on 93 octane with my turbo install in the spring, but thats strictly due to the forced induction and spark and timing ..etc. I have used 89 prem on my pcm4less tune and i see no difference vs the regular 87 i used to before except slightly better millage on the highway and slightly more power. I have 150,xxx

Did you have it tuned for 89 octane from PCMforless?

 

[ConeKilrAutoX]

Did you have it tuned for 89 octane from PCMforless?

Yes, sorry i meant to say that

 

[OctaneRider03]

What's up brother? This was what I've found to be a very interesting question for one to have answered. I felt your pain a few months ago while my reflash was going down.

PCMFORLESS asked me which octane rating I wanted my fuel set at after I told them my specific desires as far as what all I wanted my truck to do, I told them 93 on the ordersheet. After the PCM came back my buddy put it back on and noticed awesome results as far as pick up goes, but told me that he was instructed to ONLY use 93 from then on, as it's been reprogrammed to only except that particular fuel grade.

I can't recall everything that he said, but the bottom line is, if they said only 93, that's all it's been fed.

93 does burn cleaner, which is in a way "better" for any engine to my understanding. But let's face it, we don't drive 6.0's (I don't as of yet but SOON!!) our 4.2's don't say ONLY 93 either.. I mean let's be real here..

It really doesn't matter what you put into it, but just to be on the safe side after your reflash, don't push the warning you know? I fed mine 89 once after the reflash and have a strong feeling that it may have caused one of my plugs to foul out.. Not sure though, it WAS fouled out but it could have been a number of reasons. Hah, good luck bro! -Lee

 

[OctaneRider03]

Oh yeah, I totally forgot to mention that he said something about something "knocking" should I had put in a fuel grade that's not accepted by the truck. Can't remember exactly what he was talking about though.. -Lee

 

[jimmyjam]

higher octane allows you to run more spark advance. properly timed ignition give a more efficient power stroke. low octane fuel is less "predictable" and you run the risk of premature detention or knocking
i haven't looked much at the i6 tables. in the v8 tune, there is a high octane and low octane spark table. supposedly, if the engine sees knock, it will work its way down to the low octane table. also, it supposedly works its way down faster than it works back up. so a tuner may be more liberal with the low octane table vs a more conservative stock tune to avoid having the tune go limp if it sees some bad gas.

 

[OctaneRider03]

higher octane allows you to run more spark advance. properly timed ignition give a more efficient power stroke. low octane fuel is less "predictable" and you run the risk of premature detention or knocking
i haven't looked much at the i6 tables. in the v8 tune, there is a high octane and low octane spark table. supposedly, if the engine sees knock, it will work its way down to the low octane table. also, it supposedly works its way down faster than it works back up. so a tuner may be more liberal with the low octane table vs a more conservative stock tune to avoid having the tune go limp if it sees some bad gas.

Yet another SAVE by JimmyJam. He said it all bro! Everything I wanted to say, he brought it all to the table.. Good luck dude!

 

[bore_pig]

I had mine tuned for 91 octane and a cai. The overall effect of the tune gained me just enough mileage to cover the cost of the higher octane gas. My performance gain was very noticeable.

With stock tune and tires I could not do a brake-stand. Stock tires were 245/70-16. (approx 29.5"x9.5")

With pcm4less tune and 31x10.5-15 michelin a/t tires I could brake-stand all day.

With pcm4less tune and 285/75-16 duratrac tires I cannot brake-stand, but I can get a chirp occasionally on cold pavement. (approx 33x11.25)

 

[Mypetropig]

I believe you can get about 2-3 extra ponies going to 93 octane. I'm sure you cant feel those measly ponies but its what they can do with the timing/spark table etc. that really gets the but dyno going. You can run 89 if tuned for 93 but it may knock, if it does it will pull timing and power/fuel economy suffer. My TB is tuned for 89 and I can feel the difference if I put 87 in it as well as hear it knock a bit.

 

[RayVoy]

higher octane allows you to run more spark advance.

Jimmy has it nailed.

Your given a check list by the tuner, behind the scenes, in the shop, the programmer simply codes in additional spark advance when you ask for a higher octain fuel. Additional spark advance usually provides additional horse power.

 

[HARDTRAILZ]

Got my pcm set up for high octane but had a full tank of 87 in it.Will see if it feels different when I put in 93 this week.

 

[jimmyjam]

Got my pcm set up for high octane but had a full tank of 87 in it.Will see if it feels different when I put in 93 this week.

you may want to unplug your pcm to reset it when you do that to force it to the high octane table. i've heard rumors that it resets when it sees the gas refilled after key on but i can't verify any of that.