: can '98 Northstar be tuned to take Regular Gas?

02-11-05, 12:03 AM

I know the latter Northstar engines will take Regular grade fuel. The 98 still says to use premium. Is this something that could be adjusted for? Or do I just have to use premium all the time, as indicated?

Can I damage the engine by using Regular?




02-11-05, 12:24 AM
The knock sensor used in the Northstar is very effective, and will retard the timimg wiht lower octane fuel to prevent knocking, and detonation. It will not hurt the car, but it is recommended that Premium be used. Some people have noticed a small decrease in performance and some haven't. Overall, if your really need to, it will run fine with no real problems.

Aurora By Olds
02-11-05, 12:27 AM
I've been running regular in my '95 for the last 5-6k miles. I notice no difference whatsoever, other than extra $$ in my pocket.

02-11-05, 01:48 AM
Regular gas could cause excesive carbon deposits and lead to other issues including oil consuption due to ring glads clogging. However drive it like you stole it and it'll stay clean out and higher octane isn't required but...... Higher octane better performance.. a catch 22

02-11-05, 03:22 PM
You'd have to find a way to lower the compression ratio if you wanted to run regular gas without fear of detonation. Thicker headgaskets come to mind, or perhaps porting the heck out of the cylinder heads. Or dished pistons...

In my personal opinion, I would not use regular in a northstar engine. The reasoning is this - while the knock detection circuit is state of the art, if something breaks (knock sensor, the wire from it... etc), it won't detect the detonation in time to retard the timing, and you'll be minus one engine. I personally think it's too risky to be worth the benefits.

Besides... gas is what? $1.80 a gallon? 1.85 for premium? I think I'm getting 26mpg. what's the problem? Pay the extra $1 per fillup. http://cadillacforums.com/forums/images/smilies/icon_rolleyes.gif

02-11-05, 03:31 PM
Well, what about the middle one. The 89. I've been using this one. The car runs great. Is this ok?

02-11-05, 05:00 PM
Regular gas is just a lower octane. Octane is nothing more than the fuels resistance to detonation. It does not cause excesive carbon deposits. It does not increase oil consumption. And you do not need to make any adjustments nor reduce compression ratio. Using it will cause no harm. As previously mentioned the knock sensor will retard the spark acordingly. If you are going to race it and want the absolute peak performance, burn premium. Otherwise save your money. I have been running regular on Bbobynski's advice for almost 3 years now and I have noticed no change at all, performance or MGP.

The 4.9 is another story as it has no knock sensor.

02-14-05, 12:43 AM
I'm surprised at some of your replies - you've been on this forum long enough to have seen this question beeing asked several times.

To the original poster: It seems that the N* engine will detect the lower octane gas (with the knock sensor) and it will "detune" itself to properly run under those conditions.

For more info, search this forum for "regular gas northstar" (without the quotes).
You might also want to search for "octane".

Good example is:

This is from our resident Cadillac expert.


02-14-05, 07:43 PM
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