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Grand Prix GTP Eaton M90 Supercharger Oil Change Guide
Pictures and instructions on how to change the supercharger oil in your Eaton M90 supercharged vehicle.

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This supercharger oil change guide is intended for any vehicle that is equipped with the Eaton M90 or M112 roots style supercharger.

These vehicles include the 6th generation (1997, 1998, 1999, 2000, 2001, 2002 & 2003) GM Pontiac Grand Prix GTP and also the Buick Regal GS, Monte Carlo SS, Impala SS, Ford Lightning, Ford Harley Davidson F-150, and certain Ford Cobra Mustangs.

Although this guide was specifically written for the Eaton M90 supercharger unit, it might be useful for owners of the Magna Charger Radix MP112, Paxton NOVI, Whipple, Vortech, ProCharger, Jackson, Powerdyne, and other Eaton  supercharger models.

Owners of the supercharged Nissan Frontier SC and the Xterra SC, or certain Chevy, GMC, and Hummer SUV with blowers may also find this guide helpful.


To the right you'll see my 2001 GM Pontiac Grand Prix GTP with a 3.8 Liter Eaton M90 Supercharged 3800 Series II V6 engine.

The Eaton M90 and M112 are self contained roots style superchargers with their own oil supply.

The manual says to just check the oil and top off every 30k miles, but other GTP owners have recommended a complete oil change every 50,000 miles.

Pontiac Grand Prix GTP

There are three main types of superchargers including centrifugal, twin-screw and roots style.

My GTP has an Eaton M90 roots style charger.

The first step to changing the supercharger oil is to remove the engine cover by unscrewing the bolt just above the "3800 Series II Supercharged" text on the cover.

Also remove the engine oil crankcase filler cap.

3800 Series II 3.8L S/C

Then locate the snout of your Eaton M90 or M112 supercharger and the belt that goes around the pulley.

The stock pulley on a Pontiac Grand Prix GTP is 3.8". By putting on a smaller pulley you can force the supercharger to spin faster and produce more boost and hp.

The stock boost rating of my M90 is 6 lbs (pounds).



Next, get your two 4 oz (ounce) bottles of GM Vehicle Care Supercharger Oil, which is part number 12345982 at any GM dealership or at online retailers such as Amazon.

You'll also need a sprayer top and some sort of bottle to hold the old supercharger oil. The old oil will really stink so be prepared for that.

GM Supercharger Oil

This picture shows you exactly where the supercharger oil change bolt is located.

As you can see, I have a 3/16" size Allen key sticking out of the bolt head to illustrate it's location.

You can also use a 3/16" hex head socket.

Once you remove the bolt, you can insert your totally clean and dry spray bottle pump head tube. (You don't want to introduce any water or foreign substances into the supercharger oil reservoir chamber.)

Supercharger Oil Tank Bolt

Once you get most of the oil pumped out of the supercharger, try to move the pump's hose around to get any more that is hiding in the crevices of the M90.

Then you just have to use a small funnel and carefully fill the supercharger up with oil to just under the bolt threads. Don't Overfill Your Supercharger!
Now go have fun and enjoy the WHINE and power of your supercharger!

For more, check out all of my Pontiac Grand Prix DIY Repair & Maintenance Guides.

Pumping Out Old SC Oil

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