Accidentally put Premium for First Fill-up...

[Drive By Fire]

That being said on my most recent fill up I decided to give the 91 a try to test it out for myself. I haven't noticed any difference in performance but I have noticed a 1L/100km decrease in fuel economy.

On my first fill up they asked what grade to put in, and I didn't know, seems silly but I just hadn't thought to look. So I said 91. I was thinking there was no way high compression, high boost would run on 87. I was wrong.
Coming from a performance car where my tune from 92 to 93 net me about 3 hp, no one's car in here is more responsive or smoother. It's exactly the same no matter what grade you're using at the pump.
Attached is my last car after my first revision and the difference to a finished tune.
Edit: Stock tune is ~230whp/240wtq. I finished right around 290/330

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[Drive By Fire]

[QUOTE="Troy Jollimore, post: 65636, member: 4355"The higher the octane count, the more controlled the 'explosion' of the fuel is, so lower octane gas is potentially more 'dangerous'.[/QUOTE]
Higher octane is a slower burning fuel. The fact the fuel is in a cylinder and added in carefully controlled amounts makes it not dangerous. lol

 

[Troy Jollimore]

Heh. If you're that knowledgeable about tuning you know what I meant... Ever seen a piston that was subjected to long periods of detonation?

 

[Drive By Fire]

Heh. If you're that knowledgeable about tuning you know what I meant... Ever seen a piston that was subjected to long periods of detonation?

Sure have. It ain't pretty.

 

[Troy Jollimore]

Sure have. It ain't pretty.

That's the danger I was talking about. As for the 'no performance without a tune', that's not the case as the ECU advances the timing to take advantage of the better fuel. Small change, though.

 

[Drive By Fire]

That's the danger I was talking about. As for the 'no performance without a tune', that's not the case as the ECU advances the timing to take advantage of the better fuel. Small change, though.

I think you're confusing how the ECU adjusts for fuel. The scenario you're describing only works if you require 93 and accidentally put in a lower grade, in which case the ECU will cut timing and such to prevent Kr. As better fuel is available (fill half a tank with 93 lets say) you will get some timing back until full 93 is present.
It won't add power to an ECU tuned to perform on 87. It is just throwing money away.

 

[Drive By Fire]

A better example is a car that adjusts for E on the fly. If you put 93 in daily, and maybe hit the track on the weekend and you add E85 to your tank, the ECU will adjust accordingly.

 

[Troy Jollimore]

I think you're confusing how the ECU adjusts for fuel. The scenario you're describing only works if you require 93 and accidentally put in a lower grade, in which case the ECU will cut timing and such to prevent Kr. As better fuel is available (fill half a tank with 93 lets say) you will get some timing back until full 93 is present.
It won't add power to an ECU tuned to perform on 87. It is just throwing money away.

So I would hazard the tuning on our cars is probably set for 91, but will easily retard for 87.

 

[Drive By Fire]

So I would hazard the tuning on our cars is probably set for 91, but will easily retard for 87.

That I'm not sure of. to me the negligible gains (if any) are not worth the cost to me.

 

[Troy Jollimore]

That I'm not sure of. to me the negligible gains (if any) are not worth the cost to me.

Exactly. My Passat states 91, but I ran 87 in it for a bit because it was just a commuter. I never 'floored it' at all. The engine would run fine... I've noticed my wife's Vibe is pinging when going up hills part-throttle. Switching to 89 eliminates it.

 

[Gavnzdad]

Hey guys, new member here. I'm not sure if this has been posted before, but just got a new EX-T a week and a half ago and I was due for my first fill-up today. Went to a local BP and I could've sworn I hit the 87 button initially but after I finished, I saw that I was charged for 93! I'm paranoid right now as to what will happen with the engine, especially once my second fill come up. Will it be ok the 2nd time if I put 87? Thanks again all!

OH MY GOD!

You really screwed up. That hot of a fuel will cause your muffler bearings to seize up. Might even foul out the glow plugs. You need to put some sugar in the tank to counter act the higher octane.

Nah, just funnin'.... you'll be good bud.

 

[Drive By Fire]

Exactly. My Passat states 91, but I ran 87 in it for a bit because it was just a commuter. I never 'floored it' at all. The engine would run fine... I've noticed my wife's Vibe is pinging when going up hills part-throttle. Switching to 89 eliminates it.

Under no circumstances should you ever go below minimum octane rating. In my hypothetical situation, I should have been more clear. I was not talking about the stock map. It's very common on flex fuel vehicles to utilize the factory alcohol sensor to adjust maps on the fly. Or, like in my case, I had other maps available to flash if I needed (valet, limp, 91, 93). All the aforementioned scenarios would require a OBD-II accessory, and a professional tune.
As far as "The engine would run fine" statement. Sure it runs fine, until it doesn't. Granted, it would appear it survived life under your ownership. Assuming it's sold, I hope the new owner knows better.
That makes about as much sense as saying "My engine runs smoother when I change the oil."

 

[Drive By Fire]

I've noticed my wife's Vibe is pinging when going up hills part-throttle. Switching to 89 eliminates it.

Switching to 89 from what? Also the GT, or base model? Cause the GT had the peppy motor. Very high compression, for the time anyway. haha

 

[lamichlein]

Hey guys, new member here. I'm not sure if this has been posted before, but just got a new EX-T a week and a half ago and I was due for my first fill-up today. Went to a local BP and I could've sworn I hit the 87 button initially but after I finished, I saw that I was charged for 93! I'm paranoid right now as to what will happen with the engine, especially once my second fill come up. Will it be ok the 2nd time if I put 87? Thanks again all!

My Touring got 41 -42 mpg with Shell no ethanol high 91 octane . But after reading previous fuel comments here I asked at my Honda service Dept about fuel...

I was told to use mid grade 87 no ethanol but not to run higher because the engine doesn't run hot enough to burn it off and it would leave a varnish that they regularly use an additive on in the service Dept to reduce buildup. Also I saw here in the forum that the Honda engineers worked hard to create a system that used regular grade for economy.

So keeping it simple...I use mid grade (87octane) and often cannot find less that 'up to 10% ethanol' here in the Midwest. I only get 39.2 mpg but remembering it is economy we are striving for in the touring model the extra cost of premium is not worth the additional mpg. The engine runs smooth no issues.

 

[Troy Jollimore]

"...don't run hot enough to burn it off and would create a varnish..." Errr, yeah. I'd take that with a grain of salt. Especially since motorcycle carbs get gummed up WITH varnish that forms faster from the Ethanol blends you get at lower octanes. Honda's made these things to run on 87. Fine. But everyone seems to come up with fantastic stories as to why nothing else will work. And I'm coming from the VW world. Where if you don't do everything EXACTLY as the OEM states, you'd think you were causing Armageddon the way everyone screams and cries disaster!

Under no circumstances should you ever go below minimum octane rating. In my hypothetical situation, I should have been more clear. I was not talking about the stock map. It's very common on flex fuel vehicles to utilize the factory alcohol sensor to adjust maps on the fly. Or, like in my case, I had other maps available to flash if I needed (valet, limp, 91, 93). All the aforementioned scenarios would require a OBD-II accessory, and a professional tune.
As far as "The engine would run fine" statement. Sure it runs fine, until it doesn't. Granted, it would appear it survived life under your ownership. Assuming it's sold, I hope the new owner knows better.
That makes about as much sense as saying "My engine runs smoother when I change the oil."

Ooooh... Them's FIGHTIN' words, boy! I disassembled and rebuilt my Talon almost to it's component parts, so I know a little of what I talk about. Let's see, many owners on the PassatWorld and other forums running 87 for YEARS with no issues, no knock even. Though again, they usually don't go full throttle to anger the detonation gods with the turbo. Especially since I'm running a performance chip. The computer still just rolls back the timing to prevent detonation. Not optimal, but not destructive. We're talking about really conservative settings here, not something that will explode because an injector misfires for a split second or two...

The Vibe? Just a base model. Switching to 89 from 87 (91's our highest)... It ran fine for years, but the pinging started about a year or so back. My wife insists she can't hear anything and that nothing's wrong. Maybe it'll go away with new plugs. The original Iridiums are getting closer to the end of their lives since they have 100k miles...

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