Fuel, premium vs regular

[fajitas21]

Tossing this out there as research, considering these are industry experts attempting to use Dynos and data to address this.

https://www.youtube.com/watch?v=ryqyTPfNj1Q&ab_channel=MotorTrendChannel

 

[bloc]

Tossing this out there as research, considering these are industry experts attempting to use Dynos and data to address this.

https://www.youtube.com/watch?v=ryqyTPfNj1Q&ab_channel=MotorTrendChannel

Interesting. Almost no difference in ignition timing needed between 87 octane and 116.. with the caveat that if someone were boosted or running a high compression ratio it would be a whole different story.

 

[TeCKis300]

Tossing this out there as research, considering these are industry experts attempting to use Dynos and data to address this.

https://www.youtube.com/watch?v=ryqyTPfNj1Q&ab_channel=MotorTrendChannel

There's multiple dimensions here and context is important. This is on a simple big block with carbs that doesn't have some more modern technology that can vary volumetric efficiency. A dyno pull on an engine stand focusing on peak power numbers may not tell the whole story. There's other variables and use cases that can be tougher on an engine, like when it's installed in a chassis with extended loads and heat.

The video shows that certain designs may not have faculty to leverage more octane, to actually produce more peak power. Another dimension is that while more octane may not produce higher peak numbers, it might be able to maintain better power under really stressful use and loads like racing or towing in the middle of summer, where it doesn't have to pull as much timing or run as rich to maintain temps to keep detonation at bay.

Though the 5.7L is a more modern design with variable valve timing, on both intake and exhaust, that can more greatly effect volumetric efficiency and dynamic compression depending on tuning.

Translation for the LC, run what it was designed - 87. There may or may not be benefits to using more octane.

 

[bloc]

There's multiple dimensions here and context is important. This is on a simple big block with carbs that doesn't have some more modern technology that can vary volumetric efficiency. A dyno pull on an engine stand focusing on peak power numbers may not tell the whole story. There's other variables and use cases that can be tougher on an engine, like when it's installed in a chassis with extended loads and heat.

The video shows that certain designs may not have faculty to leverage more octane, to actually produce more peak power. Another dimension is that while more octane may not produce higher peak numbers, it might be able to maintain better power under really stressful use and loads like racing or towing in the middle of summer, where it doesn't have to pull as much timing or run as rich to maintain temps to keep detonation at bay.

Though the 5.7L is a more modern design with variable valve timing, on both intake and exhaust, that can more greatly effect volumetric efficiency and dynamic compression depending on tuning.

Translation for the LC, run what it was designed - 87. There may or may not be benefits to using more octane.

No carbs on that engine.

 

[TeCKis300]

No carbs on that engine.

The link above doesn't work for me. I watched episode 97?

I didn't watch the whole vid and just jumped to the conclusion where they re-jetted the carb for methanol. Looks like it was a mash up of two episodes. Comparing octane and alternative fuels.

Doesn't change my comments.

 

[Hillbilly Deluxe]

What you want to hear maybe something else. Leaving it to anecdotes of others, none that I have heard with any formal understanding or background in the matter, some that don't even own an LX and are suggesting for you to put something on the line, should be taken with a grain of salt.

As a tuner in a previous life, and professional background in tuning aircraft motors, I will only fill mine with 91 octane. No, I don't believe it'll results in catastrophic failure, but later in life, may result in premature things like lost compression, carbon buildup causing even more knock, catalytic converter failures, etc.

If there's anything you should take away, do not alternate fuel grades on fill-ups.

You might not believe this, but I appreciate your reply and insight from experience. I can handle the tough love. We will use premium from now on. Again, thank you.

 

[scottm]

First tank that isn't 91 octane yesterday. Filled with 87 from near empty, drove to O'Hare and back and near empty again. $1 more per gallon for feeling good about myself is no longer worth it. Modern engines with all the gee-whiz tech are more capable of using that extra octane I guess, but probably more when using high-power, not so much for highway cruising.

I'm wondering if at very cold temps, could the extra octane be useable to these engines? This truck sits for days at O'Hare.

 

[onelittlestar]

The link above doesn't work for me. I watched episode 97?

I didn't watch the whole vid and just jumped to the conclusion where they re-jetted the carb for methanol. Looks like it was a mash up of two episodes. Comparing octane and alternative fuels.

Doesn't change my comments.

Link doesn’t work, just copy paste.
Translation, if you’re not boosted or running high comp, your modern engine doesn’t really care what octane first world gasoline you’re running running, it’s all the same. Also, do whatever makes you feel warm and fuzzy.

 

[bloc]

I thought I remembered this thread from somewhere..

OVTUNE says LC and LX ECU Fuel Mapping are identical

forum.ih8mud.com

 

[04UZJ100]

I thought I remembered this thread from somewhere..

OVTUNE says LC and LX ECU Fuel Mapping are identical

forum.ih8mud.com

Yeah. No surprise here.

 

[TeCKis300]

Link doesn’t work, just copy paste.
Translation, if you’re not boosted or running high comp, your modern engine doesn’t really care what octane first world gasoline you’re running running, it’s all the same. Also, do whatever makes you feel warm and fuzzy.

Thanks for the pointer.

Couple things. The 3UZ-FE isn't the same big block motors as before where only static compression is in play. There's variable valve timing on both intake and exhaust cams. Along with butterflies for Acoustically Controlled Induction System (ACIS). Long way to say that it has the ability to effect volumetric efficiency or how deep the engine breathes at each intake stroke. Which directly affects octane requirements depending on calibration.

Watched the right video and glad these guys have more depth than what is expected of youtube these days. This doesn't pertain to the LC as it was tuned for 87, but possibly the LX tuned for 91. Some pretty key phrases at 3:10 . It's not just about power.

 

[onelittlestar]

Thanks for the pointer.

just here for the positive anecdote

 

[fajitas21]

Thanks for the pointer.

Couple things. The 3UZ-FE isn't the same big block motors as before where only static compression is in play. There's variable valve timing on both intake and exhaust cams. Along with butterflies for Acoustically Controlled Induction System (ACIS). Long way to say that it has the ability to effect volumetric efficiency or how deep the engine breathes at each intake stroke. Which directly affects octane requirements depending on calibration.

Watched the right video and glad these guys have more depth than what is expected of youtube these days. This doesn't pertain to the LC as it was tuned for 87, but possibly the LX tuned for 91. Some pretty key phrases at 3:10 . It's not just about power.

Agree with your comments.

And note - I didn't state an opinion on here as I don't know. I just wanted to provide additional data that could help people have a more justified data point.

A few things of note in the video:

Freiburger (if you don't know who this is look up Roadkill on Motortrend - a legend) addresses knock resistance, agrees detergents among brands are different, and also address the dyno can add load instead just a set amount of resistance.

He also discusses things like Fuel Injection - boosted engines - and VVTi (camshaft comments) and acknowledges this is for a Blueprint - static compression - NA engine.

I shared this only to illustrate the extreme speculation on forums and "the way we did things" is hard to overcome with data, and it's even harder considering there's so many variables (na vs boosted, carb vs fi, etc). They are just doing their best to try to understand - I like that on the show they speculate at the beginning about how they think it works, then test, then challenge their speculations with data and see if they can draw a reasonable conclusion. Many episode end with them realizing they were wrong for 40 years about something. One good episode about that where they all 3 were wrong was about backpressure creating power... It's only interesting if you're nerdy about this stuff, but from your other posts I feel you'd appreciate the content as you are a technical person at heart.

 

[bicycleagent003]

It's a different world. With modern EFIs, it's possibly to tailor engine tunes to fuels. An LC may be an LC, but in this case, an LX may not be an LC. Many bring up mechanical equivalence in static compression, part numbers, etc. That's missing the point because electronic controls, i.e. software, can very much modify dynamic compression and octane requirements.

Thanks for your informative comments on this thread.