I read somewhere adding excessive oil is not a good practice,I don't know whether adding 12 oz of Auto-rx after oil&filter change is excessive or not,is it safe to add auto-rx directly after oil&filter change or what amount of oil is recommended so that it will be not excessive after adding auto-rx.
Auto-Rx is NOT an oil or a solvent . Auto-Rx does not change your oil chemistry. Within a few hundred miles of driving Auto-Rx it is on metal ( oil is just a carrier) it is up to you if you wish to drain oil and replace with Auto-Rx. For myself i would add 12 ounces (providing I have 5 quart oil reserve ) and start application.
I'm kind of confused, the new instructions simply say to add 12 oz of Auto RX. "Step 2 - Change oil and filter. Add one 12 oz. bottle of Auto-Rx®." The old instructions broke it down by your particular oil volume, the new ones do not.
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2001 Ford Ranger, 4.0 V6. Mobil 1 0w-30, Motorcraft FL 820s filter, 3oz Auto Rx
You are correct. The new instructions have been simplified, hopefully making it easier for everyone to follow. For some this will mean using more ounces of ARX, but keeping it in the crankcase for a longer period of time.
I can't imagine that an engine can't tolerate 12oz ..or even 24oz overfill. Where this became an issue is where the profile of the car got lowered and the sump still remained our traditional 5 quarts. That's when you began to see "max overfill" on some dipsticks due to the crank whipping up the oil into a lather (aerating it). I haven't heard of this being an issue of merit for a very long time. I think that the manufacturers found out that many dealer bulk delivery systems were too variable and suffered added costs due to them. Admittedly, that part is pure speculation.
I surely can see the need for simplification too. KISS is the key to consumer level success. If you put too much information in the instructions, confusion will occur.