I hate asking this question as I'm sure it has been asked 1000000 times. I tried search and didn't come across anything that really helped.

My question is this, Do I need to put Premium Gas in my Cadillac DeVille?

The owners manual says so, the IP says so...But I've heard a lot of people tell me I don't need to.

I've been putting 93 octane in my DeVille since I bought it about 12 months ago.

So my questions are these,

1.) Must I put Premium (93 Octane) in my DeVille?
2.) Will I lose MPG if I switch to lower octane?
3.) Will using a lower octane cause any damage?
4.) Will I have serious knock issues and power loss from using lower octane fuel?
5.) If all of this is made up, why did Cadillac tell me I have to use Premium Fuel?

1. No
2. No
3. No
4. No
5. The Northstar has a knock sensor that will retard timing as soon as it detects a spark knock. Obviously there will be some performance loss but none that you will notice. I have been using regular for over 3 years now and have noticed no difference at all. Premium is recommended for peak performance. If your gonna race it, use premium.

Damn I've wasted a lot of money over the past year :crying:

Been there, done that. Live and learn.

I have been putting regular in mine for the past two years.

I just switched over to 87 octane four months ago on my '99 N*...only downside is slightly less mpg. The engine don't seem to mind the lower octane at all.

I have been running regular in my 99 Deville for 10K miles and all is well. I still get 28 mpg on the highway, and performance hasn't suffered enough to notice.