87 vs 89 octaine (1 Viewer)

[Benji]

I run the cheapest gas. Usually that means 87 octane. When Catrina hit, all that was left in town was 91 and it was sell'n for the same price as the 87. Well, no difference in performance or MPG, but it's only an n=1.

I'll continue to go cheap.

 

[cahilc]

Gas, is gas, is gas ...

It all starts the same.

The difference is the additives the companies put in to increase octane, cleaning, winterizing, etc.

There's a test called the BMW 100,000 mile test and we as consumers use to be able to get the results. Bascially it measure valve deposits after running a motor on a particular gas for 100k miles. Haven't been able to get the results for comparison lately.

Anyway it's most important *not* to have your motor ping for long. This includes *soft* pings.

Think of it this way. Each time your engine *pings* you loose a grain of metal the size of a piece of sand from the inside of your motor. Short term no problem. Long term ???

Cahil

 

[Mark W]

Think of it this way. Each time your engine *pings* you loose a grain of metal the size of a piece of sand from the inside of your motor. Short term no problem. Long term ???

Cahil

Can you elaborate on this please? I'd like to see something to back this up?

The "ping" is rattlng of the rings in their groves and against the walsl from the violent impact of the excessive pressures generated on the combustion strike due to pre-ignition. That is the combustion process starting too soon and/or developing too fast and impacting the piston instead of cushioning and then pushing it.


In more severe conditions it progresses to "detonation". THIS can burn material off of the piston. Lots more than just sand sized particles though. It can also crack and shatter pistons, crush ring lands and even bend rods. It's a lot more than "ping" though.


But this is irrelevent to this discussion. You will not get detonation or even significant pre-ignition in a properly tunedand adjusted 2F running on pump gas.


Mark...

 

[cahilc]

...

Can you elaborate on this please? I'd like to see something to back this up?

...

It's just the best explanation I've come up with when some layperson asks ... 'Why do I care if my engine pings ?'

Your explanation is more technical but try having that understood by somebody who asks you why you should change your engine oil ???



Cahil

 

[FJ40Jim]

Hmmm... I've heard that before somewhere.

Shameless theft is the highest form of flattery! ;p

Maybe in Outer Bumfukistan on a holiday weekend you might run into problems.
Buy the cheapest gas you can find and be happy.

...And that's another good one to remember.

 

[billmc]

Maybe in Outer Bumfukistan on a holiday weekend you might run into problems.
Buy the cheapest gas you can find and be happy.

...And that's another good one to remember.

You mean aside from being a tasteless ethnic slur?

 

[Mark W]

You mean aside from being a tasteless ethnic slur?

Not meant as such and I don't think that it should be taken as such.

If there is a place called Outer Bumfukistan, I apologize to the residents for infering that you have gasoline supply and quality problems.

I guess to be "disney rated" I could have said in "Outer Nowhereistan". Or Southern Imlostia" or some such.

Or I could have been specific and accurate: "...In some of the western African countries where they punch holes in oil pipelines to steal crude to brew gasoline in their own stills in the woods..."


Whatever.


Mark...