Testing premium fuel in the hybrid

[rtphokie]

I’m using 91 more for engine health than mpgs, however. Like a vaccination against the dreaded but rare knock disease. Trust the Science.

I'd be interested in seeing more about the science here. None of the threads on this subject have offered any science however.

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[AVC]

The hybrid does not advance timing with higher octane.

Do you have the data to support that claim?

 

[AVC]

I'd be interested in seeing more about the science here. None of the threads on this subject have offered any science however.

Yep, it seems to dissolve into the bunny trail (turbo guy) or the difficult to objectively measure; MPG changes, or the purely anecdotal and opinions; whether the hybrid *should* respond to different octane, or ...what I originally posted.....

 

[AVC]

The 2.5L is mapped to 87 octane. Anything above 87 will provide zero additional benefits.

However, I wish you well in your research.

Same; any data to *prove* that?

 

[Mavster Mechanic]

Do you have the data to support that claim?

Yes.

Why would I lie to you?

 

[HeyBales]

Now this is a test I'm not wasting scanner logs on.
Or rather, not wasting a tank of gas on, just to get scanner logs showing timing advance differences.
Ok, for grins and giggles I'll try to remember to add some PIDS about it to current tank of gas.
The remember is the hard part there.

 

[GmanGM]

Yes, it will make a difference in the EB but this thread is about the hybrid. From what I've read it's not going to help the hybrid at all.

Pretty much a waste of money - if your engine requires 91 by all means do it, if it doesn’t and it’s not knocking- don’t ) oh btw - if it is knocking you probably need a timing adjustment/tune up- not a gas change). Wtf do you want to pay a dollar a gal (33%) more for something you don’t need- basically it’s like getting 33% less milage???? If you really really want this insurance you stated, then go up 1 grade to midgrade for $.50 cents per gallon more, geez. But to “trust the science” as u say, the just go w what is manufacturer recommended.

 

[h1k3rb]

Pretty much a waste of money - if your engine requires 91 by all means do it, if it doesn’t and it’s not knocking- don’t ) oh btw - if it is knocking you probably need a timing adjustment/tune up- not a gas change). Wtf do you want to pay a dollar a gal (33%) more for something you don’t need- basically it’s like getting 33% less milage???? If you really really want this insurance you stated, then go up 1 grade to midgrade for $.50 cents per gallon more, geez. But to “trust the science” as u say, the just go w what is manufacturer recommended.

Yeah, I'm not doing it but like all of us, the OP has to do something with his time and if it makes him happy to test it out, why not.

With that in mind, we know modern computer controlled engines will retard timing if it detects pre-detonation, aka - knocking, so there's no reason all engines couldn't be capable of advancing timing as far as possible to take advantage of higher octane fuel when detected. Seems like a no-brainer to me but we've been told that doesn't happen unless engines are designed to run on premium.

 

[Ranko Kohime]

I'd be interested in seeing more about the science here. None of the threads on this subject have offered any science however.

I read that to mean you'd like to know more about how premium fuel affects the combustion process, and/or how we measure it, hopefully I got that right.

Octane relates to how resistant the fuel is to detonation, which is when the fuel ignites earlier than we want it to, such as early in the compression stroke. This can lead to the fuel trying to push the piston down during an up cycle, sending all of that energy into decelerating the engine, rather than accelerating it. Obviously not good for the engine.

ETA: A thought occurred while writing further down to mention that gasoline can "diesel", that is, ignite without the aid of spark, if pressure and heat are high enough and octane is low enough. Unlikely to happen unless you were to run <85 octane in a high-compression engine near sea-level, though.

Spark timing is advanced prior to Top Dead Center because fuel takes a while to get burning, and starting the burn prior to the piston reaching TDC gives the spark time to ignite the entire fuel/air mixture. Which can tie in with detonation. The computer pulls back timing when it detects detonation, reducing the impact. The sensors are far more sensitive than our ears, catching signs of detonation while to us, the engine is still running perfectly well. This is what normally happens when you run 87 in an EB, for example, it just pulls back the timing and probably reduces boost from the turbo, as additional fuel/air increases the probability of detonation.

The metrics that the vehicle reports via OBD-II, should be that load is reduced while detonation is detected. Whether the 70% average load I observe is simply the efficiency sweet spot for the 2.5L, or if it's holding back, is what I intend to test here.

 

[Chops]

The 2.5L is mapped to 87 octane. Anything above 87 will provide zero additional benefits.

However, I wish you well in your research.

The 2.5L is mapped to 87 octane. Anything above 87 will provide zero additional benefits.

However, I wish you well in your research.

Of course, the 2.5l can remap itself to 91 as recommended by Ford for “severe” conditions. 2.5l adjusts - but does not judge.

 

[Cherokee]

Hybrid, regular fuel, Any higher octane is useless unless your overloading it and knocking occurred.

Ecoboost/Turbo, Premium is good in the summer not as much advantage in the winter.

 

[dochawk]

however the question is still raised, at least in my mind: does the effective compression still benefit from a higher octane?

For any given compression (including from turbo) and timing, octane comes in two categories:
1) enough
2) not enough

You can also detect when you're getting to the edge between them(colloquially, "pre knock").

Once you're into "enough", all the extra octane in the world doesn't make a difference.

Now, you *could*, with variable timing and/or compression (variable displacement or adjustable turbo boost), start questing to more aggressive timing or higher boost, creeping up a bit at a time, but the engine would need to be designed to do this. However, every explanation of an engine that I've seen so far goes the other direction: start with what you would do with high octane (91 or 92 for Northstar, reportedly 97 for ecoboost), and go down from there.

anyway, to be clear again: if you have enough octane, there is no advantage to more at that boost/timing combination.

oh, and FWIW, in the final major overhaul of the Northstar (2000), they just plain gave up on premium and programmed for 97. Northstar's before that are quite happy on 87; they just lose something like 15 HP.

ETA: A thought occurred while writing further down to mention that gasoline can "diesel", that is, ignite without the aid of spark, if pressure and heat are high enough and octane is low enough.

A Daimler engineer got to name the new model after figuring out ignition by spark. He named it for his niece, Mercedes.

Of course, the 2.5l can remap itself to 91 as recommended by Ford for “severe” conditions. 2.5l adjusts - but does not judge.

To "remap" itself, it would need to be able to advance timing. AFAIK, there have been exactly zero reports suggesting this capacity on the maverick 2.5

 

[DadJokesGalore]

BP, Shell and others have more detergents in their premium octane.

Best to do your own research for the brand of gas you use since there may or may not be a difference. I use Costco which uses the same detergent level across octanes.

 

[Chops]

To "remap" itself, it would need to be able to advance timing. AFAIK, there have been exactly zero reports suggesting this capacity on the maverick 2.5

I was responding to the comment that the “engine is mapped to 87 octane”.

So you’re saying when Ford recommends 91 octane under “severe” conditions - it does not “remap”, but instead has more of a “cushion” of octane as the 87 enough/not enough gets stressed?

That would be simpler and more effective than my (imaginary) “remap” thanks!

 

[HeyBales]

I was responding to the comment that the “engine is mapped to 87 octane”.

So you’re saying when Ford recommends 91 octane under “severe” conditions - it does not “remap”, but instead has more of a “cushion” of octane as the 87 enough/not enough gets stressed?

That would be simpler and more effective than my (imaginary) “remap” thanks!

Are you still talking hybrid which this thread is about?

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