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I was changing the cabin air filter on Penguin LS (my son's 2012 LS MT) and noticed the KRD code on the glove box label. This engine, like the 1.4 engine in the 2012 LT, ECO, and LTZ, is also coded for 91 octane. I had tested 91 octane in his car a few years back and it does indeed run slightly better on 91 than on 87. Now I know why. It appears the Gen 1 LS engine is also being protected by sophisticated knock sensors.
 

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Well color me surprised, it doesn't have a ridiculously high compression ratio, wonder why they want premium?
 

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Well color me surprised, it doesn't have a ridiculously high compression ratio, wonder why they want premium?
The 1.8 has a compression ratio of 10.5:1. Saw the spec sheet for myself when my brother bought his 2012 ls. Fortunately I was there to ask that question as the salesman pointed at the 138 hp spec on the info board. He ended up taking me to a back office computer and brought up the full spec sheet for me to see.
 

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The 1.8 has a compression ratio of 10.5:1. Saw the spec sheet for myself when my brother bought his 2012 ls. Fortunately I was there to ask that question as the salesman pointed at the 138 hp spec on the info board. He ended up taking me to a back office computer and brought up the full spec sheet for me to see.
On par with most modern non-DI N/A engines.

I could see it helping with a heat soaked engine or low RPM power. Our Toyota has the same CR and runs slightly better on 89 than 87 on a hot summer day with the A/C cranked. 93 makes zero difference in that.
 

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The 1.8 has a compression ratio of 10.5:1. Saw the spec sheet for myself when my brother bought his 2012 ls. Fortunately I was there to ask that question as the salesman pointed at the 138 hp spec on the info board. He ended up taking me to a back office computer and brought up the full spec sheet for me to see.
10.5:1 is not really a high compression ratio. Once you're over 11.5:1 then maybe I can see recommending 91+ octane. My MX-5 by comparison is running 13.0:1 and an older ford triton 5.4L will be running 8.4:1 so 10.5:1 is kind of in the middle of the spectrum. Almost all of your non-turbo average family sedans and crossovers will be running similar compression and those won't recommend premium.

I just think it's odd that an engine that wasn't designed with the highest level of engineering, thrown into a base model economy car destined to be a fleet vehicle, would code it to run premium fuel. My guess is the recommendation is coming from Opal overseas where the 1.8L engine is a more premium engine than the standard 1.0L engines they're used to.
 

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On par with most modern non-DI N/A engines.

I could see it helping with a heat soaked engine or low RPM power. Our Toyota has the same CR and runs slightly better on 89 than 87 on a hot summer day with the A/C cranked. 93 makes zero difference in that.
The L61 in my sunfire is 10:1, no change in mpg between 87 and 93, but a big difference in idle quality. I switched it as soon as I found out and two days later I noticed it no longer had the rough idle. On a side note, that car had a hole blown in the piston at 49k. I wonder if that had something to do with it
 

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My MX-5 by comparison is running 13.0:1
DI engines can run much higher CR's on 87 because fuel isn't injected into the cylinder until it hits TDC. Better spray pattern, too. Don't need to worry about compressing the fuel and pre-igniting it.
 

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IMO old school had it right. Higher compression higher octane. DI though is a whole different ball game.
 
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