Choosing an Oil

Auto RX Worldwide Inc | ‪Ecologically Remove Engine Sludge

Choosing a Motor Oil for Your Cleaning Application

If you read our article about Auto-Rx® Plus, you will see how Auto-Rx® Plus is compatible with all 4-stroke motor oils. However, for the best results, conventional, mineral-oil based motor oils work best. The normal cleaning and rinse phases of an Auto-Rx® Plus cleaning application are only for a relatively short duration of 2,000 miles. In nearly all cases, conventional oil will provide the same level of lubrication as would an expensive full-synthetic motor oil for such a short duration. Auto-Rx® Plus is more active in simple conventional oils.

  • If you feel that you would prefer to run Auto-Rx® Plus with a Group IV full-synthetic oil, then merely increase the cleaning time to 4,000 miles and do the same for the rinse phase for 4,000 miles (no Auto-Rx® needed).
  • If you are running Auto-Rx® Plus to solve a rotary seal leak in a motor, using conventional oil is a must for both the cleaning and rinsing phases.
  • For heavily sludged motors, we highly recommend running conventional oil for cleaning and rinsing. We recommend that you do not run oils badged as “high mileage” for the best cleaning and rinse results in heavily soiled motors or those with seal leak issues.

Auto-Rx® Plus works best with dino or conventional oil for the short 2,000-mile oil change interval. Note: It is possible to run Auto-Rx® Plus with whatever oil is recommended for your motor in the proper weight and viscosity, but the cleaning might not be as efficient as with conventional oil. Many oils are available on the market that can be run for extended oil drains, but keep in mind that running the engine with extended oil drains may result in the same problem that caused the trouble in the first place.

If you choose to run Auto-Rx® Plus in a full-synthetic PAO-base oil (such as Mobil 1), you must increase the cleaning phase and rinsing mileage to 4,000 miles. PAO-based oils do not accept additives readily. They need coupling esters to hold the additive package in suspension. These coupling esters compete for the same space on metal surfaces as do the cleaning esters of Auto-Rx® Plus, which slows down the cleaning action and takes longer. Also, the PAO oils are not a good choice in the rinse phase because those coupling esters make the oil cling to metal, which interferes with Auto-Rx® Plus being able to rinse the metal surfaces fully. Therefore, if you use this type of oil, the cleaning process may not work as well as with conventional oils. All engines, including turbos, work well using conventional oil with Auto-Rx® Plus.

Some oils to consider for use when cleaning with Auto-Rx® Plus:

      • Shell Rotella T
      • Castrol GTX
      • Pennzoil in the yellow bottle
      • Pennzoil Group III Platinum
      • Mobil Super 5000
      • Conoco Phillips
      • Trop Arctic

As stated a number of times on this page, choose an oil in the proper weight and viscosity for the given vehicle. Auto-Rx® Plus is more active in conventional oils, or Group III oils that have mineral oil as the base. If you wish, you can go back to a full synthetic after you have finished the Auto-Rx Plus application. Just remember to use the Auto-Rx® Plus Auto-Rx® Extended Protection Plan.

Our Advice? Don’t waste money on expensive oil designed to run longer intervals. Auto-Rx® Plus generally works best with the least expensive motor oil available. Choose an oil in the proper weight and viscosity for the given vehicle.

For Rotary Seal Leaks:
Conventional oil must be used
For Heavily Sludged Motors:
Use conventional oil for best results


Regardless of the oil you choose, Auto-Rx® Plus can do no harm,
but the results will not be as good if you choose to use other than a conventional oil!

Need technical answers? Have questions? See our Instructions page

© Auto-Rx Worldwide, Inc., Jacksonville Beach, FL USA. All rights reserved.

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