Opinion: 91 octane is superior. Especially if you have an MT

Hold your tongue!

Great document attached.

We're 11.8:1, but 87 works. That is strange as anything over 10.5:1 should be at least mid-grade.

My ST4 is 10.5:1 and rock 87 on a simple open loop EFI that nets at least 41mpg over the last 11yrs riding like a hooligan.

 

lol I too like to watch $200 burn for no good reason...

Think about how many EAF stickers I can buy with that monies..

 

Membership or card rebate? If membership, then fucking cheers!

Yeah. You and I jawed about that a bit. We moved here in 1996 from PA and still miss Eagle Hardware. They were just better.

The amount of aimless construction going on hurts my mind.

We're looking for the eject handle. Possibly Woodinville until the kids get done with school, then something east (Duvall-ish) or north (B-ham).

We only ate at that Black Angus once. It was not good. We do miss Chevy's though.

 

I have no idea. I've had that pic since 2012.

It's in my goto files of motivational posters that still make me laugh.

 

There is more bang for the buck running the lowest possible octane that works. The higher the octane the tamer the burn. There is more power in an explosion than there is in a mild burn. Running a high octane in a low comp engine will make carbon, which will raise the comp though When you have built about 1/4 inch of carbon on the top of the piston the comp is wildly higher That carbon holds the heat and that engine will run on like an old Celica, backwards!

Ride it like you stole it !

 

Octane requirements are just as much (if not more) determined by timing than compression. High compression burns faster (which requires a slower burning, higher octane fuel) but timing will have a far greater impact on when the mixture starts it's burn.

 

Exactly.

If I could have done that, $35k would have been my total also. Still, I NEEDED reliable wheels. 4yrs of continuous wrenching on a fucking Ural was enough, plus some mechanical fun on my other bike.

 

My Indian Springfield is high compression and requires high octane fuel. If I don’t use it, it causes knocks.

My taco on the other hand does not have a high compression engine and runs just fine on 86 octane. I can use 91 or 92 and the net gain is only for the fuel company. It does absolutely dick for mileage in these trucks.

It’s called physics as you stated. All high octane does is resist burn rate. If your engine isn’t designed for it, it can’t take advantage of its properties. People are fooled by the “premium” labels and think the gas is somehow magically going to turn your ride into some sort of super truck with extra hulk-like power and supernatural MPG gains. Yeah, good luck with that...

But hey, if you want to fund the oil companies by all means go ahead. It’s your money....

 

Very true. The first time that I pulled the heads on the ST4, they were carboned up like crazy. The original owners (brothers) only used premium. Since with 87, it has a thin layer of tarnish that more or less wipes off.

 

I cannot understand how and why?

 

Filled up 87 on Monday, home and work round trip is about 44 miles total, average freeway commute with LA traffic results in the following for me.

 

Finally some fucking sense. Unless OP can provide evidence, I'm going with "all in their head."

 

Yeah, I tried some 91 in my MT truck this past week just to see if there is a difference. There is a difference, especially under low rpm and high load (ex: accelerating out of higher gear). The engine shuddering is reduced but not eliminated. And, generally, it is a smoother power delivery across the board. But, IMO, those subtle differences don't justify the cost of the fuel. Also, my MPG did not improve at all. I will be going back to 87 next week.

 

Ah, another octane thread. Haven’t had one of these for a while.

 

The answer to your question is no. It comes in the form of cash-back which you can use to purchase at Costco or apply it to your CC balance.

 

Actually the FKS engine IS a high compression engine (11.8:1). The DI fuel delivery provides cylinder cooling similar to what octane does for gas. The ISSUE with this engine is when the ECU switches from Port to DI. That is not a seemless transition and is where the shuddering comes from. It is my opinion that the higher octane helps with this transition.

 

https://www.hemmings.com/blog/2014/...the-fiction-behind-those-higher-priced-fuels/

 

On the membership, yes, but on the card, it can be cold, hard cash. That is what we did this year.

 

Uh huh. I give my unicorn extra special high magic feed. It makes his skittles farts even sweeter too.

Around here you can get 86 octane. I can spend an extra 10r 20 cents per gallon and use 88 or 89 or go full retard and go 91 or 92 but my truck does not knock, shimmy, rattle or shake at 86, so just what is it I’m gaining exactly?

Read the article I posted above.

 

Maybe by you but around me 93 is usually a dollar more than 87. So more like a thousand a year. And its not a budget breaker but more what am I getting for that thousand dollars?