i dont pound on the car, but have never heard it ping due to low octane. i only use 94 octane a few times a month if i am city driving, not on the highway.

so does the computer adjust for the octane and prevent lean issues. my previous car was a turbo buick, so i am familiar with low octane sounds.


i read were turbo cars get beat on and due to low octane the engines cant hold up. i feel its just getting beat on that is their hardship.

thx dave

 

The computer has two spark advance tables, one for low octane and one for high. However, that's doesn't mean GM sets both to be different. It depends on the engine. In the case of the 2.4 and 2.0, they do, but it doesn't look like they did on the 2.2. Actually, I think the 2.0L has a spark table for each cam and it averaged them so it must have 4 tables or something like that.

GM has detonation protection built into the PCM and it does a good job of protecting the engine. If you defeat it or reduce it's action, then yes you can damage the engine quite fast if it's boosted. Just running a low octane gas in a turbo engine isn't bad, it's just bad if the detonation is severe when the engine is under load. And then, the damage depends on the conditions when it happens. There is no broad statement that can be made like "running low octane gas in a turbo car will damage it". That is not immediately true. It *can* damage it but that doesn't automatically mean it will. Heck, you can tune a turbo engine to run on 85 octane if you want. You just won't get as much power.

If you are just cruising around, 87 isn't a problem on the 2.0L. If you do go into boost and it detonates the PCM will reduce the advance to remove it. You will feel the power tend to flatten out (or drop). The risk to damage is very, very little. GM isn't interested in replacing engines because the someone used 87 octane. It's not good press. GM tells you to use 91 or higher so you don't complain about surging or sagging in the power. They require you to use 91 or higher with the stage 1 because it will *definitely* surge and sag and you will *definitely* complain and they don't want to hear about it. But the PCM will protect the engine. If someone told me they ran 87 octane the whole life of the engine, I wouldn't immediately think it's destroyed. That is just not true.

 

righteous.
thx dave

 

I have over 50K on my SS and have runn regular 89 octane in it for all but 4 - 5 tanks. I also drag raced a 67 Camaro with 13.75:1 compression running 9.80's in the 1/4 so know what detonation sounds like. I have never heard any pinging even with hard driving on the SS. If I took it to the track I would put the good stuff in as it may run more consistant but I don't feel that at the stock boost levels at 500 feet above sea level there are any detonation issues. Always remember the higher you are above sea level the thinner the air is and the more likely you could need higher octane to prevent detonation. If you have ever seen a hole burned in a piston you know that detonation is not a good thing :)

Russ