Hi,
Have used this and gotten any mpg or performance gains?

 

Where fuel will make a difference in these engines is in the choice between "real gas" (ethanol free), Top Tier, and the rest. You'll get the best mileage and performance out of real gas, and second best out of Top Tier. If you run anything else, you'll get the worst in mileage, performance, and engine life, too. So don't do that -- it's cheaper to pay more for quality fuel than to pay for premature engine wear.

Our engines don't have knock sensors, so there's nothing at all to gain by running a higher octane than that which doesn't result in spark knock. Engines that have knock sensors will often get better mileage and performance out of higher octane fuel because the lower octane stuff results in knock, which the PCM discovers and to which it reacts by retarding the ignition timing. But we don't get that bit of magic, so pouring in a higher octane than you need is just wasting money.

 

The V-10 I have my dad bought new in '95, so it's stayed in the family.

We have ran everything through it (well, not Diesel or E-85)

With the premium it does get a bit better mileage, but not enough to offset the cost of the fuel.

So it's usually plain old 87 octane.

It gets 9-10 mpg, loaded, empty, head wind, tail wind, 9 to 10 MPG.

Unless we're plowing snow, then with all the backing up, the mileage drops considerable.

 

Regardless of what some say, your truck will run better and have more power when using the higher octane gas. I used to run 87 octane gas in my truck, and it seemed like it had no power and didn`t run as well as it should. I switched over to 91 octane gas, and its a night and day difference. My truck has more power and runs considerably better, so I don`t run anything but 91 octane in my trucks. To me its worth the extra money.

 

You clearly don't understand what the http://en.wikipedia.org/wiki/Octane_rating represents. Live like you want to live, but it's poor form to BS people.

From the referenced Wikipedia article (emphasis mine):

 

I`m not trying to BS anyone, I`m stating a fact based on my personal experience.
Try it for your self, run three tanks of 87 octane, and then three tanks of 91 octane, and you will notice an improvement in power and a small improvement in gas mileage.

 

Are you seriously saying that petrochemical engineers know less about gasoline than you do?

I'm not saying that I am a petrochemical engineer; what I'm saying is that when I seek facts I go to qualified sources for them. You're making claims that all qualified sources say are untrue, so whether you're aware of it or not you are BS'ing people.

 

OP here. Thanks for the insights. My '99 2500 runs smooth on 87 and my studies last couple days basically confirm no benefit to speak of. I changed the 02 sensors even though no check engine light and the plugs but still 9-10mpg on digital read out. (4.10 diff) Interesting that when people use higher octane no mention is made about maybe changing plugs to a hotter heat range. Would this make some sense? I read that the QC9MC4 is 3 ranges cooler than RC12...?

 

I have the SCT tuner with the 87 tune on my V10 currently. With the crappy winter fuels at the pump, I'm running 89 octane in it and am getting 8-9 overall. Strictly highway driving gets 13.5. Changing to 91 or 93 octane gives no gains on that tune. This is with 35" tires and 4.10 gears.

Before the SCT, I tried the hotter plugs thing with higher octane and it just made ping worse, much worse.

 

Just for future reference: The light will eventually come on to tell you that you've got a flaky oxygen sensor, but your truck will be running like crap long before it does. Weeks or months before.

Nope, sure wouldn't. Especially in these engines, going to a hotter plug is just begging for detonation problems no matter how high the octane rating of the fuel.