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interesting subject on Northstar engine


skyman

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Just something I thought was interesting about the Northstar. While doing some research on the dogbone torque mounts on the DeVilles, I looked through many, many adds for these cars on Auto Trader.com.I looked at many photos of the engines plus photos of the rest of the cars.

I noticed that on all the Eldorados with the northstar engine, the photos of the gauges showed "use only premium unleaed gas" while Devilles of the same years and same engine did not show this and only require regular unleaded gas.

Any thoughts or "facts" on this?

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I'm a newcomer to Cadillac ownership, enjoying my '98 deVille with the Northstar engine. I asked a similar question early in the process of familiarizing myself with

the car, and was told that while it will burn any grade, all but the Premium will result in a loss in fuel efficiency and performance -- ten percent or so. And since

I pay only about ten percent more for Premium fuel, I have decided not to go against the engineering, and to burn only Premium fuels. I get almost 25 MPG on

the road and I'm presently getting 18.4 MPG in my daily drives around town. I'm really very pleased...so I'm going to stay with the recommended fuels.

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The model year 2000 saw a change in the head design for more turbulence at lower RPM and the requirement for premium fuel was dropped. Premium fuel is recommended for best performance but not required for model year 2000 and later Northstars.

As voicepro says, many people do run their 1993-1999 Northstars on regular gasoline or intermediate grade. In most cases the knock sensor and the PCM adjust for the lower octane. The tradeoff is lower performance and economy levels. Another point that I haven't seen addressed is that the lower levels of additives associated with regular or intermediate grades of gasoline is that the detergent additive levels are lower, so that the car is more likely to need throttle body or injector cleaning over time.

I never used anything other than 91-93 octane in my 1997 Eldorado except for one half-tank the day before a hurricane came ashore near my home.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Thanks Jim

Very good and technical info. ...a bit over my head :>)

I'm only assumming that the engine in the 97 DeVille is the same as the engine in the 97 Eldorado. The readout under the gas gauge on the Eldo says "premium unleaded only" but on the DeVille it doesn't.

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I have almost 135,000 miles on my 2006.

In the first 20,000 miles I experimented a several times with running regular because of the cost differential...

My Owners Manual highly recommends Premium.

It does say that Regular can be used but cautions you that there will be a loss in performance and fuel mileage.

I found that to be true.

I lost a little over 10% in fuel mileage and the car took a VERY NOTICEABLE HIT performance wise.

I probably drive mine a bit more BRISKLY than most Cadillac owners do, so the performance drop was very noticeable to me.

Since than, nothing but Premium has been put in it.

The cost is no more than using regular, and it runs so much better.

By the way, throttle body has never been cleaned and it has no symptoms that it needs to be cleaned.

I do need to replace the plugs... not because of any problems... but because they have almost 135,000 miles on them.

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There are two tunes for the 1993-199 Northstar, 275 hp and 300 hp (with variations of 5 hp or so for different models with their exhaust systems). If the eighth digit is a "Y" the car came with the 275 hp version, and if it is a "9" the car came with a 300 hp version. The 2000+ Northstar VIN "9" engine is 320 hp, more or less.

The VIN "9" cars have a model number with the middle letter "T", as ETC, DTS, or STS, which stood for "Touring."

The 1993-1999 VIN "Y" and VIN "9" engines differed only in the intake camshaft. I don't know what the difference between them was after 2000.

In 2000 there was a redesign of the combustion chamber that allowed regular gas. The compression ratio remained at 10.3:1. There was no notice in the owner's manuals for 1993-1999 that regular gas was acceptable.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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