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Use 93 Octane Or Not?

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93 Octane? The debate continues...

21632 Views 47 Replies 21 Participants Last post by  pL2014
I have been reading all of the internet, mostly on this forum, over the debate of filling up the Cruze with the highest octane fuel. I have had my 2012 Cruze LS 1.8L since December of 2011. Until the last two times I have filled up(past 3 years), I have used regular gasoline. But recently, I was told I need a fuel injection cleaning and told that if I simply put in a bottle of fuel cleaner as well as use Shell V-Power, that would do the trick.

I did do that and the two times I have done it, I have noticed much better performance out of my car. Not only better performance, but better millage too. I did read in the Cruze manual and it states about using at least regular unleaded fuel (87 Octane level). But the manual states you can use higher octane if you wish.

Everyone I have spoke to about this thinks, "it's a bad idea", "it's not good for your engine". Both people who know cars and others that have just had more experience with cars.

I don't see what can be the downside to using higher octane gas in the Cruze.

What are your thoughts? I am stuck with what to believe.
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To the OP....higher octane ratings will not harm the engine in any relax.

There can be diminishing returns though.
In the case of the Cruze, it seems either engine design responds favorably to higher octane numbers.
Evidently, there is enouph available ignition advance to take advantage of the higher knock resistance that 91/93 provides and, because it can 'light the fire' a bit sooner in the compression stroke, you can get the same power with a smaller throttle opening.
That, of course, results in the mpg enhancement and a driveability improvement, often described as a peppier or more response to throttle feeling.

We, as a group, have noticed this is particularily noticeable in high heat, high load (A/C operating) around town driving where engine temperatures are at the upper edge of normal.
The engine has a tendency to 'spark knock' under these conditions and the computer retards the ignition timing to prevent mechanical damage.
The operator notices a delay in throttle response and a mileage decrease that disappears when operating with the higher octanes.

My eco auto around town average increases by a bit more than 3 mpg using 93 in the hot summer months as opposed to 87/89 regular.
But, as soon as ambient temperatures are consistantly below 60 degrees (f) I can match the mileage using 87/89 and because the air is cooler the tendency to retard the timing is reduced and driveability improves.

Moral of the story, for me, 93 for best mileage and driveability above 60 degrees.....come fall, back to regular.

The other side of the of my many vehicles is a 97 Chevy C-1500 long cab, long box, 350 v-8 auto.
It doesn't care what octane you pour in it......18 to 21 mpg....cold, hot, fast or slow, runs the same hot or cold, air on or not.
It makes it clear that small displacement engines can show big benefits from small changes, larger displacements (both stock) don't.....or at least, rarely measureable.

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Unless specifically called out for your car, don't waste your money on higher octane fuel. Octane is merely a measure of a fuel's resistance to autoignite (i.e. knock). It has nothing whatsoever to do with the energy content and will not provide more MPG in and by itself.
Until I added this 1.4T to the fleet, you and I sung from the same book.

But, we all have found that this engine has a strong tendency to pull timing the moment it hears any semblance of knock/ping/pre-ignition, whatever term you like.
With that timing pull comes a looooooong flat spot on throttle reapply, say after making a turn.....and to clarify, I'm 64 and my car flogging has become almost non existant (not to be confused with dead).

However, we (I) also have found this computer has a LOT of advance available and, as a result, in particular ambient temperatures above 60f, it will have rather favorable results using 93.
The 'bog' or flat spot mentioned earlier virtually disappears and, in my case anyways, the mileage improves by almost 4 mpg around town, offsetting the additional cost.
I might add, the around town mileage improves the most and I'm likely in the 90% around town range.

In my case, the highway mileage improves as well, but not enough to offset the cost.....a bit over 1 mpg.

Regardless of mileage, and the car gets great mileage regardless of fuel......I rate it great or on 93, greater yet, I prefer the warm weather driveability improvement that 93 particular with the A/C operating.

In your case, all I can say is try a couple tankfuls and see what happens.....a very inexpensive experiment at that.

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