You can’t draw any conclusions about how efficiently the car is running by how “responsive” the car feels to the driver. You do that by logging fuel economy and maybe some 1/4 runs or some time on a dyno.

If you’re running a car on 87 when 91 is the minimum recommended, either the knock sensor tattling to the ECM or it’s not, and the ECM is either retarding the the timing, or it’s not.

If the engine is getting a 91 spark advance with 87, it’s like a virtual spark advance. That would explain your perception that it “runs better” but it could also be running with frequent spark knock or detonation, and that can go unnoticed with a turbo.

You are playing a dangerous game. Aluminum motor + turbo + detonation = sudden unplanned full stop.

Follow the manual recommendations. If you want to experiment, maybe hook up a scanner that will log the knock sensor?

 

Appreciate your reply. Will follow the manual. I was just trying to understand why I am noticing better performance with the lower octane. But its better to be on the safe side.

 

Do you have blue Bosch 3 bar sensor on the front top part of your engine? Just above the fan. If it's not one of those, you don't need 93. The GMTU came with those blue 3 bar sensors if it's tuned with that kit.

 

Okay will check and post the result. I have no idea but will check. I truly love my SS and it runs well besides the occasional sluggishness. I think it may just need some proper tune up. Currently it has the stock air filter and I heard that something like K&N can help but I also heard that the oil on the filter can be an issue.

 

The K&N filter can help, just make sure it’s not over oiled! Either use paper towels to absorb the excess oil or wash it and reoil it sparingly.

 

I know it’s subjective but an HHR SS should not feel sluggish. If it’s slow or inconsistent, there is something wrong.

if there is something wrong, performance mods are an inappropriate solution.

How many miles on the car? Auto or manual?

Make sure everything is OK before modding, and keep in mind that performance mods are a good way to hasten the demise of an aging power plant.

First scan for code if you haven’t already. If that turns up nothing, do a compression check.

I think gas quality is becoming more of a problem, and some states require zero quality inspection. I am especially suspicious of premium from low-volume stations. Ask car enthusiast in your area who has reliably high-quality gas.

 

Okay thanks a lot. I used K&N a while ago on a different car with no issues but cars are different and so one has to be careful. But eventually I may have to use it on my SS.

 

I wonder if this is what you are talking about. I have attached pictures. It does say 'Bosch' at the top.

 

Hi, so its Automatic with 160K Miles. Got it about six months ago. No codes currently that I can see unless there are codes that can only be seen by a special tool. I have tried different stations with slightly different result. Currently I am leaning towards Exxon. I did use a can of Lucas a while ago and I was thinking about using another one. Thanks.

 

No. He was talking about this Bosch sensor (red circle). It's called a Tmap sensor.