I data logged this a few times as I was learning hpt and when I ran 87 the pcm would pull 2-4 degrees of timing regularly on 87. This was light throttle and cruising situations. Filled up with 93 and the pcm never pulled any more timing showing it was gas causing knock retard. I never ran less than 91 again after that. The 2.4l is tuned for 91, but can run lower grades because the pcm has a fudge factor for low quality/bad gas. Consider 87 bad gas for the 2.4l. 87 will move your car, but not as efficiently as 91. Not sure how anyone could get better fuel economy on lesser fuel grade. I could see things staying close or negligible, but not better unless the driving conditions or ethanol content were different on those occasions.

 

My experience with the 2.4 has been pretty much the same as that of "hhrfreek"

On 87-oct gas, regardless of ethanol content (ie: between 0 and 10%), I was seeing KR at high-part throttle and WOT. If I went to mid-grade fuel (typically 89-oct) that usually got rid of the KR.

When I did the calibration work on my HHR w. HPTuners, I ran straight 91 but, otherwise, I use 89-oct fuel.

As for fuel economy, as long as the way you drive doesn't put a load on the engine such that the ECM dials back the timing due to detonation, the mileage shouldn't change between 87 and higher octane gas. However, if you do drive such that you're getting KR on 87, that reduces fuel mileage. Also, the higher the ethanol content in the gas, the worse the mileage.

For my own HHR, I don't care too much about fuel mileage as long as it's reasonable. Of course, in my case, "reasonable" may be less than others with OE calibrations in their ECMs because I decreased min. TPS at which PE is enabled, I decreased the PE delay and I increased PE ramp-in rate. That will decrease mileage but also makes the truck a lot more responsive and has it performing better in the mid-range RPM.

 

I have never used anything but 87 octane. It is a dream to think you will get more MPG with higher octane fuels. More power and speed maybe, but with more power and speed comes lower MPG.

Boydie Back in the Saddle..........................


"And if I claim to be a wise man, it surely means that I don't know"

 

I have run both in my 06 2.4. With the 87 mine will get some preignition for the first 1-2 seconds of start up in the morning until the ecm can retard the timing.

 

Bump, for valuable info

 

I don't understand why people would buy a car that wants 91 gas but put 87 in it anyway. Using the data from my last fill up with 91, I spent a little bit over $4.00 total vs filling up with 87.... a small price to pay for my engine to run smoothly.

 

the car requires 87..not 91 or 93 or whatever you want to put in there. The ecm will fix knock so put in whatever grade you like! its your preference...whatever makes you sleep better at night.
BUT if you are tuned, then thats a different story, since you are going after performance etc.
It all just depends on how and where you drive

 

skyline:from the owners manual

If the vehicle has the 2.4L L4 engine (VIN Code V) or
the 2.0L L4 engine (VIN Code M), use premium
unleaded gasoline with a posted octane rating of 91 or
higher. You can also use regular unleaded gasoline
rated at 87 octane or higher, but the vehicle’s
acceleration could be slightly reduced, and a slight
audible knocking noise, commonly referred to as spark
knock, might be heard.

 

This!

I don't want to hear any knocking or loss of performance from a car that I bought and expect to run and sound the way the factory want it to run and sound. We are talking about $4 (give or take) per fill up. Small change in the big picture.

 

I can vouch for this first hand. I was unaware this car requred premium and used and use a lot of 87 el cheepo, I thought something was wrong with the car or transmission, ran like it was pulling a trailer. I filled up with 93 earlier this week, car sat for two days and this morning it runs completly different...much better nite n day difference.