Real Benefits to 91/93 Octane in a regular LQ4???

anyone really seeing benefits to using 91/93 octane in their regular LQ4/6.0 V8???

I have not been one of those that believed higher octane on vehicles that don't recommend/require it got any benefits...I've owned vehicle that did recommend/require it and always used it in those vehicles but tried in other vehicles, I saw no benefit...

as a test I tried a full tank (currently) of 93 octane and noticed what I believe is a slightly better or smoother running of the 6.0 and definitely no ping when under load...I will also add that the ping happens so infrequently as to not be a big plus but I noticed it yesterday driving on the expressway...MPGs might be 1 MPG better...

that said, I am not convinced this isn't the "placebo effect" I am experiencing as it is only 3/4 of a tank in but...

what say all of you???...I just drive my 2005 Yukon Denali, never tow, rarely have more than me and maybe one other so...

please feel free to share your thoughts and experiences...'round ChicagoLand it is about $1.00 more a gallon for 93, 89 isn't worth the cost or effort and mostly, 87 seems just fine but for what I've mentioned above

thanks,

Bill

There is an active thread here that discusses this issue ad nauseum, which you can view. Make some popcorn first, so that you do not starve to death while reading through the thread.

Many varying opinions and many facts, but definitely not a consensus of opinions, though.

Thanks

if you own a tuner (i own one, so its way to easy to play around) i ran 93 only in my 5.3, added some timing across the board and felt more power, and got better mpg. once 93 went back up to over 4 bucks a gallon. i tuned it back to stock and run 87 now. that first tank of 87 sucked so bad with the loss of power.

If you are able to look at the factory tunes with a program like HP Tuners or even TunerPro, you can see the big difference in the "High Octane " and "Low Octane " timing tables. Now the ecm has no way of knowing what Octane you have put in the tank. But it watches the knock sensors and from what I understand it floats between the High and Low tables as it sees knock. If it sees no knock it will stay on the more aggressive timing table. Thus, the POSSIBILITY of better mpg. I saw this with my father's 2002 LQ4 2500 truck. It would consistently get better mpgs on premium... but not better enough to warrant always running the more expensive fuel.

If I remember after work tomorrow, I'll pull up a set of high and low timing tables for an LQ4. Not sure I have one for an LQ9, but I'll look. But I'll post them and you can see the difference.

Watching one of those Engine Masters dyno session on Motor Trend TV the other day. They tested gas from 87 to racing 116 octanes and E85. Blueprint HiPo 6.0 with EFI. Saw about 3 HP difference from the lowest to highest octane and that was with tuning for timing and AF ratios. No real advantage in any of the fuels. I was pretty surprised at all that.

I've seen the Engine Masters episode as well as the Car and Driver tests...yesterday I did a bit of driving on the expressway and entering or passing still heard the slight pinging when under heavier load...I feel no additional "power"...I still believe that without a tune I won't see much of a benefit and certainly nothing to justify $1.00 more a gallon...

thanks so much for the advice you've shared here...it is appreciated

Bill

It's not so much a power gain by running premium as a power loss by not running premium. As stated above, the PCM adjusts timing based on input received from the knock sensors. The higher octane, the more resistant it is to detonation, which can damage an engine. A higher compression engine will be more susceptible to spark knock (detonation), so that is why premium is recommended/required. Using a lower octane fuel can result in more spark knock, which will remove timing and cause less power. It may or may not be noticeable, but if you were able to look at data logs and live data, you would absolutely see it. It can also have an impact on MPGs. You can contact any tuner and they will confirm this. I'm sure blackbear performance on here would be a great one to reach out to as they tune these vehicles daily, for years.

And worth noting that most tests are at wide open throttle with air/fuel ratios at 12.5 : 1 or so. Running at part throttle at a much leaner mixture in real world conditions the higher octane might, or should, be worthwhile at the higher cost? I've always run at least mid grade gas in our recent GM motors with the higher compression.

SilverSport said:

I've seen the Engine Masters episode as well as the Car and Driver tests ... yesterday I did a bit of driving on the expressway and entering or passing still heard the slight pinging when under heavier load ... I feel no additional "power"... I still believe that without a tune I won't see much of a benefit and certainly nothing to justify $1.00 more a gallon ...

thanks so much for the advice you've shared here ... it is appreciated

Click to expand...

Pessimistically, 1 gal of gas equals 10 stop'n'go miles. Optimistically, as much as 25 highway.
So a 25 gallon tank (never run it bone dry) should cover between 250 and 625 miles.
Price of 91 / 93 in NYC is about 30% higher than the price of 87.
250 * 1.3 = 325 miles ... 625 * 1.3 = 812 miles

If 91 / 93 doesn't improve mileage by enough to offset its additional cost, then save your money.