Cognitive dissonance and low octane fuel.

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BMWTurboDzl

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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?
 
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?



I suppose it's for the same reason that some people see the "Warning not to go below 87 octanes" as a recommendation.
 
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.
 
Yes, designed to accomodate different octane fuels, but there is a limit which some operating conditions would exceed.

The only time I use lower octane than required fuel is when I am at high altitude.
 
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?
 
Because people are cheap and drive many of them cars because they are status symbols. Then they get mad if something happens.
 
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?

If the engine is preventing it then they really do not need it.
 
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?


Yes. Someone had to require a knock sensor and install the programs in the ECU to reduce timing etc for lower octane.
That is engine design, no?
 
Last edited:
Originally Posted by JLTD
Yes, designed to accomodate different octane fuels, but there is a limit which some operating conditions would exceed.

The only time I use lower octane than required fuel is when I am at high altitude.


I use lower than "recommended" at high altitudes (live at 7000ft) or all day interstate cruise speed.
 
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?
 
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?




I wouldn't call it a feature but a fail-safe. Cruise control for example is a feature.
 
Last edited:
Originally Posted by ammolab
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?


Yes. Someone had to require a knock sensor and install the programs in the ECU to reduce timing etc for lower octane.
That is engine design, no?


It's not a feature but a fail-safe designed to preserve engine life. Kinda like a transmission which prevents the user from performing a money shift.
 
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.
 
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?


Maybe it's easier just to ask those people who insist why they insist?
 
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."
 
Originally Posted by brages
"cognitive dissonance" is a good buzzword for implying that other people are idiots...

If the shoe fits, then don't argue with the salesperson.
 
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.


Depends. If the way they use to prevent knocking is open loop and massive retard / run super rich, it is going to use way more fuel, dilute your oil, and may shorten the cat / O2 sensor live. At least when they do that they are saying that "we are not confident with it, but if you insist we are protecting ourselves". Their engineers likely have done enough work to tell the marketing not to put that on the brochure.

It might make sense when gas was 99c for 91 and 79c for 87, but it does not make sense when it is 4.39 for 91 and 3.99 for 87 on a hot summer day at sea level, because running rich will likely use way more than that.
 
Last edited:
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."


Because the AAA magazine said so.
Manufacturers are to blame for having a minimum octane rating of 87 with a turbo. Yes, I'm looking at you Honda. I can't imagine buying a CR-V and NOT buying the turbo but one can't blame the consumer when you tell them 87 octane is ok.
Someone in another thread was inquiring about fuel dilution in their cousins, friends don't remember which, 1.5 Civic turbo and how they could shift into 6th gear at 30 m.p.h. I would bet in such an instance fuel consumption goes up because i.e. 1/2 inch more throttle translates to much more fuel than same 1/2 inch in a non-lug condition. Gas pedal travel is not linear with throttle unless you have a throttle cable.
There should be a downshift light in the case of manual transmissions.
 
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