2000 Cadillac Deville the fuel issue

DESERTDOG69

MEMBER
2000 CADILLAC DEVILLE
V8
FWD
AUTOMATIC
46,000 MILES

Hi. Currently i'm on my second caddy with the northstar engine. The older one, a '97, I ran the premium gas all the time. With the newer one, i've been running premium but, as we all know, gas is getting to be a "premium" on it's own!

i've read thru a hundred articles online about the difference between 87 proof and 91 proof gas! It seems to me that it all boils down to the engine's compression ratio. A "typical" compression of 8 to 1 is good for "regular" 87 proof gas!

my question: what is the compression ratio on my '00 northstar cadillac engine?

i can't seem to find this information anywhere! Although, my gut tells me that running her on the less proof gas will only create problems and may even screw with the computer! Please help me out here! It's at a point where a tank of gas is an easy eighty+ dollars!

thanks for your time and information!
Michael

1 Reply

MMPRINCE4000

MECHANIC
8,548 POSTS

Compression up to 2000 was 10.3 to 1, which would probably require premium fuel (91 or higher).

The risk you take is pre-ignition or the fuel ignites before it is supposed to. The piston travels up the cylinder and ignites before it is supposed to (due to compression ratio) and causes a "ping". This puts severe strain on the pistons, rings, rods and crankshaft and in severe cases can cause failure to any of the above.
The PCM can compensate to some degree, by retarding the timing using a "knock sensor", but if the pinging continues, you must use a higher octane gas.
Use whatever octane the owners manual reccomends.