What Octane gas do you put in your 3800 II Montes. I was told that my o2 sensor and cat went bad because of the octane and maby some of the additives used at some gas stations. I usually go to a SUNOCO and use mid 89 not reg 87 but they said i should use higher prem 93.
What do you use???

 

i just use regular 87 octane and ive never heard of an o2 sensor goin bad becuase of octane, additives could b a problem

 

You should be able to use 87 octane in a non-supercharged 3800 series II.
In my supercharged 3800, I prefer to use Sunoco Ultra. Which for some reason in Canada is listed as 94 octane. But I think it may be the same 93 octane the U.S. has, but with a better P.R. campaign. LOL.

 

The Supercharged 3800 is designed to use 91 octane or higher.If you use lower octane you will run out of gas really fast. Don't know about the o2 sensor.

 

I have a non supercharged 3800 II engine but I am going to see if it has anything to do with fuel additives but I fill up 99% of time a a sunoco but I going to try the citgo down the street it has no additives

 

Sunoco 94 is the only gas I use on my Monte.

 

i use Shell 93 octane


i would use sunoco 94 octane, but there arent many sunoco stations around me...there is a place near the local dragstrip that sells 102 octane

 

Not sure about the U.S., but in Canada, Sunoco says they add "up to 10% Ethanol" to their gas.
They've done this for many years. I have always used Sunoco gas in all my cars. Except on rare occasions when a Sunoco station wasn't available.
Never had a problem with their gas, 87 octane or 94 octane. But there's always a first time.

 

i use 93 from Amoco/BP and Shell, but not Exxon (get about 3 mpg less on Exxon for whatever reason).

I get 2 miles per gallon over the 87 octane from the same stations... so i use the 93, pays for itself

 

I'm with Taz, I only use Sunoco for both my cars. Their 94 Octane is awesome!