Cognitive dissonance and low octane fuel.

[MNgopher]

So what is right and what is wrong?

A manufacturer that recommended mid grade or premium fuel, and an owner putting in regular. The system then protecting itself in the form of lower power.

or

A manufacturer that rates and designs its engine to run on 87 regular, but recommends premium for heavy towing or maximum performance. The system then taking advantage of higher quality fuel when it is used.

The latter is what my F150 with the 2.7 Ecoboost is. Its power numbers are based on 87 octane fuel. The Octane Adjustment Ratio (a measure of the octane used in engine adjustments) also reflects 87 as being the "norm" with the OAR generally hovering around zero (Range of -1 (Good) to 1 (Bad))

If I owned a vehicle that required premium, I'd likely fill it with that all the time. Mine does not, so I don't - unless I am towing heavy.

 

[bullwinkle]

Originally Posted by BMWTurboDzl
Originally Posted by Bottom_Feeder
Originally Posted by Imp4
Originally Posted by BMWTurboDzl
So basically if a vehicle reduces power in order to prevent damage to the drivetrain then it's a design feature?

If you wouldn't describe this as a design feature then what would you call it??

Error?
Bonus?
Mistake?
Serendipitous happenstance?
Dumb luck?

Protecting the car from it's owner.



It's almost akin to hearing someone say, "I've heard the station where I buy diesel has a problem with keeping water out of the tanks but my fuel filter pulls out the water so I'll keep buying their fuel because it's cheap."
In my experience, the cheap stations go through LOTS of diesel, because everyone goes there. Seems like it's the EXPENSIVE ones that have trouble, and it's not usually the water that gets you (unless you run extremely low & it freezes in the fuel line)-it's the black stuff that grows when water is present. Back on topic-most engines that recommend premium will pull timing with regular, costing HP AND MPGs-it just depends if the price difference is enough to be worth doing it.

 

[Pelican]

Originally Posted by BMWTurboDzl
Originally Posted by ammolab
If the engine is actively preventing knock/detonation on regular gas...IT IS designed to operate "that way"!

It just makes more HP on higher octane fuel. I would say that "Permium REQUIRED" engines are not designed to prevent
Knock on regular gas while "premium recommended" should be.


So basically if a vehicle reduces power in order to prevent damage to the drivetrain then it's a design feature?


You'll never change them, they believe what they believe and no amount of reasoning will make them see the light.

 

[Imp4]

Good gracious this thread is a mess....

 

[vw7674]

Vehicles are designed to protect the user/buyer from themselves & others.
This includes protecting the engine from the user/buyer too. So the ECU can diddle with the timing of the engine to save itself.
Think of the ECU as the engine's brain acting in it's own best interest.

 

[eljefino]

I had a volvo 940 turbo wagon. It had knock retard but ran the transmission off an old-school TV cable directly connected to the gas pedal.

If I put 87 octane in it, it made significantly less power, so I put my foot into it more, delaying up-shifts.

A more modern car is more clever about hiding this.

FWIW I ran about a 50/50 mix of regular and premium in the winter... my theory being the 87 was "fresher", good for reliable cold starts, and that of course the cold air would help prevent detonation.

 

[Linctex]

Originally Posted by UG_Passat
Because people are cheap and drive many of them ............


People are cheap and DON'T CARE!

One of the low-income single moms I do free oil changes for has a little Chevy Sonic turbo car.

I can *barely* get her to even check her oil, much less come by for a FREE synthetic oil change once every 20,000 miles!!!!!!

 

[Linctex]

Originally Posted by Pelican

You'll never change them, they believe what they believe and no amount of reasoning will make them see the light.


This statement applies to 90% of the people in "1st world society"

 

[Cujet]

Originally Posted by BMWTurboDzl
Why do people insist that simply because they don't hear knock that they can use low octane fuel when their vehicle specifies mid-high grade?

Don't they realize that they don't hear knock because the vehicle is actively preventing it because the engine isn't designed to operate that way?


One guy said I was wasting money putting 93 in a turbocharged rental car. Despite the fact that it seemed to improve it's pathetic and annoying performance.

First off, it's not his money, second, some engines have improved MPG with higher octane, mitigating any additional expense. My Jaguar will run smoothly on any octane. But as you clearly know, it's filler door has a decal requiring premium fuel.

I get 26 MPG on premium and 21.5 MPG on 87. It costs me no more money to feed it 93, and it clearly performs better on 93.

 

[Whimsey]

Originally Posted by Cujet
Originally Posted by BMWTurboDzl
Why do people insist that simply because they don't hear knock that they can use low octane fuel when their vehicle specifies mid-high grade?

Don't they realize that they don't hear knock because the vehicle is actively preventing it because the engine isn't designed to operate that way?


One guy said I was wasting money putting 93 in a turbocharged rental car. Despite the fact that it seemed to improve it's pathetic and annoying performance.

First off, it's not his money, second, some engines have improved MPG with higher octane, mitigating any additional expense. My Jaguar will run smoothly on any octane. But as you clearly know, it's filler door has a decal requiring premium fuel.

I get 26 MPG on premium and 21.5 MPG on 87. It costs me no more money to feed it 93, and it clearly performs better on 93.


That might be vehicle dependent for the difference in mpg between 87/93 octane. For our 2017 2.3 EB Explorer we ran 93 octane for the first year and recorded the per tank mpg. This was local driving and highway vacation summer driving to FL from NJ . The following year we did the exact same driving using 87 octane and the same highway driving to Fl from NJ. Our mpg was about 1-1.5 mpg less with 87 octane. Yes, the 93 octane did provide some extra "passing power" but not worth a cost of $.60+ per gallon, at least for us.

Whimsey

 

[Garak]

Originally Posted by BMWTurboDzl
Don't they realize that they don't hear knock because the vehicle is actively preventing it because the engine isn't designed to operate that way?

Or the stereo is cranked up too loud; that's a legitimate fix.

 

[DGXR]

Originally Posted by brages
"cognitive dissonance" is a good buzzword for implying that other people are idiots...

I thought it meant the OP is having inconsistent thoughts and beliefs on the use of low octane fuel.

Originally Posted by ammolab
If the engine is actively preventing knock/detonation on regular gas...IT IS designed to operate "that way"!
It just makes more HP on higher octane fuel. I would say that "Permium REQUIRED" engines are not designed to prevent
Knock on regular gas while "premium recommended" should be.

^ this
It's true there are different ways to prevent pre-detonation. But regardless of the method, if the engine is designed to adjust certain things to avoid pre-detonation, that is just the particular manufacturer's way of allowing the engine to run on different octane fuels. Again the emphasis is on recommended fuel vs required fuel.

Originally Posted by BMWTurboDzl
So basically if a vehicle reduces power in order to prevent damage to the drivetrain then it's a design feature?

Yes.
Just like a check engine light, depending on the cause/code, may activate vehicle "limp mode" to prevent serious damage. That is built-in design.

 

[y_p_w]

Originally Posted by DGXR
Originally Posted by brages
"cognitive dissonance" is a good buzzword for implying that other people are idiots...

I thought it meant the OP is having inconsistent thoughts and beliefs on the use of low octane fuel.

Originally Posted by ammolab
If the engine is actively preventing knock/detonation on regular gas...IT IS designed to operate "that way"!
It just makes more HP on higher octane fuel. I would say that "Permium REQUIRED" engines are not designed to prevent
Knock on regular gas while "premium recommended" should be.

^ this
It's true there are different ways to prevent pre-detonation. But regardless of the method, if the engine is designed to adjust certain things to avoid pre-detonation, that is just the particular manufacturer's way of allowing the engine to run on different octane fuels. Again the emphasis is on recommended fuel vs required fuel.

Originally Posted by BMWTurboDzl
So basically if a vehicle reduces power in order to prevent damage to the drivetrain then it's a design feature?

Yes.
Just like a check engine light, depending on the cause/code, may activate vehicle "limp mode" to prevent serious damage. That is built-in design.

I got in trouble for using the term "pre-detonation". I found out that I was confusing detonation with preignition.

Adjusting timing to adjust to the fuel is pretty normal. Heck - flex-fuel vehicles absolutely do that to take advantage of E85 where it can generally extract more fuel economy relative to the energy content. Even the most basic engines these days have ECUs with timing retard. They might not be able to take advantage of a typical mid-grade or premium, but they're definitely there to protect the engine.

I remember getting into a heated discussion about whether it was worth "risking an engine" by using lower octane rated fuel than recommended. This guy was saying no way should any rely on the knock sensors or ECU to protect the engine since the result of a failure would be catastrophic.

 

[Garak]

Yes. This is predetonation.

 

[DGXR]

Originally Posted by y_p_w
I got in trouble for using the term "pre-detonation". I found out that I was confusing detonation with preignition.

Adjusting timing to adjust to the fuel is pretty normal. Heck - flex-fuel vehicles absolutely do that to take advantage of E85 where it can generally extract more fuel economy relative to the energy content. Even the most basic engines these days have ECUs with timing retard. They might not be able to take advantage of a typical mid-grade or premium, but they're definitely there to protect the engine.

I remember getting into a heated discussion about whether it was worth "risking an engine" by using lower octane rated fuel than recommended. This guy was saying no way should any rely on the knock sensors or ECU to protect the engine since the result of a failure would be catastrophic.

Thank you.

Originally Posted by Garak
Yes. This is predetonation.

And thank you.

 

[Benzadmiral]

Originally Posted by Cujet
Originally Posted by BMWTurboDzl
Why do people insist that simply because they don't hear knock that they can use low octane fuel when their vehicle specifies mid-high grade?

Don't they realize that they don't hear knock because the vehicle is actively preventing it because the engine isn't designed to operate that way?


One guy said I was wasting money putting 93 in a turbocharged rental car. Despite the fact that it seemed to improve it's pathetic and annoying performance.

First off, it's not his money, second, some engines have improved MPG with higher octane, mitigating any additional expense. My Jaguar will run smoothly on any octane. But as you clearly know, it's filler door has a decal requiring premium fuel.

I get 26 MPG on premium and 21.5 MPG on 87. It costs me no more money to feed it 93, and it clearly performs better on 93.

My new-to-me '15 BMW 328i has "recommended" all over the manual: 91 as "recommended,"and 89 as "minimum recommended." At my first fill-up this weekend I put in 93, partly because there is no 91 around here, partly because I know better than to cheap out, and partly because I want to establish a baseline of MPG and performance. After that I might experiment a little, putting, say, 5 gal. of 87 to 10 of 93 for an average of 91. That could save me a big $3.00 per tank or $6.00 a month. (Which, over time, mounts up.)

Even if I don't, I suspect the increased MPG on 93 over the 21.5 my 87-drinking Buick Regal got will wash out a lot of the increased cost.

 

[racin4ds]

I simply would not own a high(er) compression late model turbocharged vehicle if I could not feed it a steady diet of premium fuel. Its just ridiculous to rely on the ECU to constantly retard timing and add massive amounts of fuel to prevent detonation in a boosted vehicle!

My '08 Legacy GT is turbocharged and says clearly on the fill door to use a MIN 91 octane. Sure it will run on 87-89 but it does not run well. NO turbocharged engine is happy on junk 87 octane, period. Yes your manual tells you its ok because they have to. Its common sense folks, with higher cylinder pressures and higher specific BHP you have to use better fuel!

 

[y_p_w]

Originally Posted by racin4ds
I simply would not own a high(er) compression late model turbocharged vehicle if I could not feed it a steady diet of premium fuel. Its just ridiculous to rely on the ECU to constantly retard timing and add massive amounts of fuel to prevent detonation in a boosted vehicle!

My '08 Legacy GT is turbocharged and says clearly on the fill door to use a MIN 91 octane. Sure it will run on 87-89 but it does not run well. NO turbocharged engine is happy on junk 87 octane, period. Yes your manual tells you its ok because they have to. Its common sense folks, with higher cylinder pressures and higher specific BHP you have to use better fuel!

On my 2004 WRX with the EJ205 engine, it was an 8.0:1 compression ratio which of course was meant to deal with the pressure from the turbo. But newer cars seem to have higher compression ratios AND a turbo.

A lot of these systems are pretty good at it. A flex-fuel engine can obviously get more MPG out of E10 compared to E85 simply on the basis of energy content. However, on E85 it's going to advance the timing, which means higher efficiency relative to the energy content. I can't imagine telling someone going on a long trip that they have to use E85 to keep the timing advanced.