A Reason to Buy Premium Fuel

[billt460]

My 17 Regal GS calls for ETHYL.

I called for Ethyl once..... But she never returned my call.

 

[wpod]

I was at my tire shop this morning fine-tuning my recent wheel balancing. While waiting, I thumbed through an auto racing magazine and came across this article. Forgive the poor quality of the pic. It was taken with the magazine balanced on my lap in poor light.

View attachment 72063

You are reading an advertisement of a product .

 

[Blagoje]

Your Accent doesn't knock like a Jehovah's Witness on 87?

There's a knock no matter what fuel (or oil filter) I use, though I will say that a surefire solution to get the knock sensor CEL to turn off is one of the following of a combination of them:

1. Run ethanol free gas
2. Run higher octane gas
3. Run fuel system/fuel injector cleaner
4. Change oil and oil filter

 

[kschachn]

There's a knock no matter what fuel (or oil filter) I use, though I will say that a surefire solution to get the knock sensor CEL to turn off is one of the following of a combination of them:

1. Run ethanol free gas
2. Run higher octane gas
3. Run fuel system/fuel injector cleaner
4. Change oil and oil filter

Numbers 1 and 4 would have nothing to do with a pre-ignition knock.

 

[Blagoje]

Numbers 1 and 4 would have nothing to do with a pre-ignition knock.

In my experience, and we all know that my first hand experience counts for nothing on BITOG, when I have gotten that CEL in some instances I either changed the oil + filter or switched to using ethanol free gas and as a result the CEL turned off. Again I am not an expert on anything but this is what I can report based on my first hand experiences.

 

[Accent Abuser]

There's a knock no matter what fuel (or oil filter) I use, though I will say that a surefire solution to get the knock sensor CEL to turn off is one of the following of a combination of them:

1. Run ethanol free gas
2. Run higher octane gas
3. Run fuel system/fuel injector cleaner
4. Change oil and oil filter

I've run gallons of fuel system cleaner and it still knocks on regular. It's never set a code it just sounds like I'm popping popcorn when accelerating at highway speeds. It doesn't knock at all on premium.

 

[Accent Abuser]

Numbers 1 and 4 would have nothing to do with a pre-ignition knock.

Not exactly, used oil has been shown to lead to lspi in T-GDI engines.

 

[kschachn]

Not exactly, used oil has been shown to lead to lspi in T-GDI engines.

Perhaps but as is often confused, LSPI is not the same as typical pre-igniton. It’s not the same mechanism and not the same effect.

 

[UG_Passat]

Seriously, that's why I run it in my vehicles. All three of them are supposed to run on 87. But my older, (1991) Ford pickup will knock and ping like crazy on anything but 91 Premium. Especially climbing uphill in the heat of the Summer. I run it in my Jeep Grand Cherokee, (5.7 HEMI V-8), because while the manual say's it will run on 87, it won't produce maximum rated power on anything less than 89 Mid Grade.

Mid Grade fuel isn't very popular around here. And when you do see it, it's not much less price wise than 91 octane Premium, so I just use that. I can't see paying $3,200 more for a high performance V-8, only to try and save a few pennies at the pump every time I fill it up. If I were that cheap, I simply would have got the standard V-6.

I run 91 Premium in my 2.5 L Toyota Camry because it has a 13 to 1 compression ratio. (2.5 L, A25A-FKS engine). I just can't see running 87 Regular in an engine with a compression ratio that is getting close to some Diesels. I'm not saying I couldn't, but again the ECU has to reduce the timing drastically in order to do it. Plus, it gets ungodly hot here in the Summer, and with 120 F ambient air going into the engine, coupled with a 13 to 1 compression ratio, I just can't see running 87 Regular in it.

However the Atkinson cycle with the intake valve open during compression to reduce pumping losses will effectively drop the compression ratio

87 runs fine on that engine

 

[billt460]

However the Atkinson cycle with the intake valve open during compression to reduce pumping losses will effectively drop the compression ratio

87 runs fine on that engine

Yes, as it will in the 5.7 HEMI. But neither will produce full performance on 87.

 

[kschachn]

I understand that. But my understanding is that the way of doing it by comparing it to a blend of iso-octane and n-heptane obviously doesn't work any more once it's pure iso-octane.

I did not know the answer to that, but it is just an extrapolation of the curve as the compression ratio in the test engine is increased. You can increase the compression ratio higher for these substances before knock is initiated.

"It means that an octane number above 100 is simply 100 plus the knock-limited indicated mean effective pressure over that of 100% isooctane divided by 3. Why divide by 3 and not use PN / KLIMEP instead? @Poutnik makes the observation that the factor of 3 ensures the PN-ON curve remains a linear extrapolation past 100."​

I found a rogue copy of ASTM D2699 and it indicates that mixtures of toluene and isooctane are used as standards for values greater than 100.

Here is a such a graph for isooctane and TEL: