You're getting confused between detonation and pre-ignition. Detonation is not great but pre-ignition can destroy an engine in seconds. There's no such thing as "pre-detonation".

The difference between 87 and 93 octane is that 93 octane is more resistant to detonation. That's it.

We're lucky that ES6T continues to post here considering the abuse he receives for sharing his knowledge.

 

I have no knowledge because I don't make what an engineer makes. According to rspi, I give all kinds of "sideways" information out... Though he has yet to provide an example.

 

I know you were a "PROFESSIONAL MECHANIC" and "PROFESSIONAL AIRCRAFT MECHANIC", but no. That is called combustion.

 

That's enough. That is what allows our, or at least my engine to use the compression, spark advance curve and turbo to have "fun" driving. Without it you will likely have pinging, and the computer will retard the spark to protect the engine and you'll lose power and MPG burning more gas but making less power. It also allows me to tow without any engine problems.

If you want to save money and you don't tow and almost never get near wide open throttle you can get by with regular. You won't have as good gas mileage and you won't get the same performance as someone running premium. You also won't achieve the MPG, HP and torque values the engine is advertised to achieve because they were using premium when they ran the tests.

As far as you "regular" guys not getting as good gas mileage none of the articles I read posted any numbers because of all the differences in vehicles and driving style. In general I'm guessing what you lose in MPG you'd still save in $$$ compared to premium.

And no this isn't my personal opinion I went in and read up on a number of regular vs premium articles.

I'm running premium and E85 to bump up the octane number, so let the E85 fight start !!!
You don't even want to know what I run in my RX-7 and what it costs

 

I'll say this... I'm sure glad I was running 93+ octane today as I blasted through several congested 18 wheeler spots on my 620 mile highway trip today. My car (with over 225,000 miles) preformed like a true sports car. Other's had to watch as I got through the congestion without any worry or problems. I simply watched them fade away in my rear view mirror.

As for ES6T, I have no idea what he is posting or what abuse you are referring to. I don't even read his activity any longer.

 

You should, you might learn something. But I guess your style is to send me a PM proclaiming you were a "PROFESSIONAL MECHANIC" and "PROFESSIONAL AIRCRAFT MECHANIC", accuse me of giving sideways information (but providing no examples) and then blocking me. Grow up.

Your car would have performed just fine on 87. May put a K&N filter in it so you can really feel the power.

 

There's a lot of misinformation in this thread.

Octane rating is a measure of fuel stability. The more stable the fuel, the less energy it contains. There is more potential energy in a gallon of 87 than 91.

Octane rating - Wikipedia, the free encyclopedia

For all our modern volvos, the car's computer relies on a fixed series of parameters for ignition timing, fuel pressure, intake temperature, throttle position, boost pressure, etc.

These parameters are set by engineers to very very safe margins. They account for all the crazy driving scenarios an owner is likely to encounter (going uphill in top gear at 120degrees towing a boat on 87 octane)

This means that as long as our car isn't detonating, it makes zero practical difference in performance. But does lighten your wallet quicker ;-)

 

But the question is are you adding to it or trying to clear it up ???

What is the misinformation as you see it ??

If you want to go uphill in top gear at 120 degrees towing a boat on 87 octane in YOUR car, have at it. Those engineers you are referring to recommend (not require) 91 octane as stated in writing in the owners manual. I for one have a heavy foot and also have modified my engine some so I'll stick with the higher $$$ of premium gas to keep from possibly punching a hole through my piston.


Detonation causes three types of failure:

1. Mechanical damage (broken ring lands)
2. Abrasion (pitting of the piston crown)

Lower octane gas may have more "potential" energy but to use it you have to time it correctly and our cars aren't optimized for regular. Higher octane gas can run more timing advance and therefore get more actual, real world energy out of it's fuel without the problematic pre detonation or pinging.

Can you run on regular? YES.
Is it safe? If your knock sensors are working, YES
Better, worse or the same mileage? Depends on who you ask, their car, brand of fuel and driving style.
Does it run as well? Not according to the Volvo engineers. It's in the owners manual.

"This means that as long as our car isn't detonating, it makes zero practical difference in performance. But does lighten your wallet quicker ;-)"
Read the manual because it does say the performance on less than high octane will be reduced. That's from Volvo, in writing.
If you need to or just want to be cheap and use low octane feel free but if you're going to express your personal view as fact you should label it so.


And this guy wasn't even towing his boat

 

[QUOTE=norcaljason;351145]There's a lot of misinformation in this thread.

Octane rating is a measure of fuel stability. The more stable the fuel, the less energy it contains. There is more potential energy in a gallon of 87 than 91.

Octane rating - Wikipedia, the free encyclopedia


Typical engineers response discounting all practical and actual experience.

 

That guy's not an engineer or he wouldn't have used the term "potential energy" when discussing fuel. "Potential energy" means something else altogether.

Nor is octane rating a measure of "fuel stability," another ambiguous term. It's a standard measure of the fuel's resistance to detonation in comparison to a reference fuel.

And I'm sick of the stupid smart person meme. There are dumb engineers out there but the problem for the uneducated - non-engineers in this case - is that they don't know what they don't know, so everything seems much simpler than it often is.

I'll give you an example. Cold air intakes. Help an engine "breathe better," right? Wrong. Pure ignorance from people who don't grasp a basic principle of operation of an Otto cycle engine, that its power output is controlled by "throttling" the air flow into the engine. If you don't know what an Otto cycle is or what throttling means, well there's probably a hell of a lot more that you don't know.

So ask yourself, do you KNOW or do you just have an opinion?