LY7 3.6L VVT V6 octane?

[Bruce Nunnally]

So the new 3.6L VVT V6 will take regular or premium octane. However, it does have a knock sensor on each cylinder, and the notes in the manual suggest that while you can use regular unleaded, performance will suffer.

For maximum performance, then, should I run premium all the time, or would it be reasonable to run premium in the summer, when knock is more of a problem, and regular unleaded in the winter when lower operating temps make knock less likely?

[JasonA]

For maximum performance, then, should I run premium all the time, or would it be reasonable to run premium in the summer, when knock is more of a problem, and regular unleaded in the winter when lower operating temps make knock less likely?

Bruce, I think when you get this far down into the nitty-gritty, only a dyno will tell you if power is suffering. I know Guru used to say that even on the older Northstars, you only lost a maximum of 5hp running regular gasoline. I doubt you'd be able to use the seat-of-the-pants dyno to answer this question -- I think you'll have to take to a mechanical dyno and put numbers to it. I use premium all the time, but that's only because the car knocks on anything less (and it knocks on premium too sometimes). Temperature doesn't seem to affect when mine knocks or not. Of course now, I live in North Carolina and I understand they DON'T use reformulated gasoline this far south in the winter like they do up north, so that may make a difference.

Or...get out your G-meter and make a few runs!

[KHE]

For maximum performance, then, should I run premium all the time, or would it be reasonable to run premium in the summer, when knock is more of a problem, and regular unleaded in the winter when lower operating temps make knock less likely?

Bruce, I think when you get this far down into the nitty-gritty, only a dyno will tell you if power is suffering. I know Guru used to say that even on the older Northstars, you only lost a maximum of 5hp running regular gasoline. I doubt you'd be able to use the seat-of-the-pants dyno to answer this question -- I think you'll have to take to a mechanical dyno and put numbers to it. I use premium all the time, but that's only because the car knocks on anything less (and it knocks on premium too sometimes). Temperature doesn't seem to affect when mine knocks or not. Of course now, I live in North Carolina and I understand they DON'T use reformulated gasoline this far south in the winter like they do up north, so that may make a difference.

Or...get out your G-meter and make a few runs!

Jason,

Have you checked the knock sensor on your car for proper operation? It shouldn't knock on regular fuel.

[Ranger]

Bruce,

On Guru's recomendation I switched my '97 Deville from premium to regular and haven't noticed any difference at all.

[justgreat]

the smaller the engine displacement, the bigger the difference will be in the loss of performmance. with the 3.6 and the weight of the cts, i don't think you would notice much difference in the 87 and 92....except in the summer where you are...probably will see a moticeable loss of power. it's heartening to hear that you're having such good luck with the car, so far. jackg

[JasonA]

Have you checked the knock sensor on your car for proper operation? It shouldn't knock on regular fuel.

I haven't replaced it yet. I removed the intake to check the connection at the KS, and to check the tightness, but all looked well. I'm not receiving any codes, so I figure it's gotta be getting lazy or something. One of these days, I'll get around to replacing it. I don't mind running regular gas, so it hasn't been a high priority (to replace the sensor). Plus, because there are no codes, I'm really not positive it's the sensor at all. I don't know a real good way to "test" it. I've heard that rapping the engine block with a hammer should cause it to detect "knock" and retard the timing, changing the idle. That may work on my grandpa's small block Chevy, but I'm doubtful you would be able to perceive any change on a sophisticated system like the Northstar. I could be wrong though!