good or bad? --> repeated use of seal swelling agents in high mileage oils

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Mar 6, 2003
College Station, Texas
Last year I remember reading something on the Exxon/Mobil motor oil site alluding to or intimating that continued use of motor oils with seal swelling agents (Valvoline MaxLife was the only one available at the time) is not advisable. I cannot find this information anymore. Now most of the major vendors have responded to the popularity of MaxLife by rolling out their own high mileage products..Pennzoil, Castrol and even Mobil (Drive Clean Plus 10-30 and 10-40) have done so. I used MaxLife in a 1993 Chevy Pickup with a 5.0L V8 and it stopped the oil leaks almost immediately...I was quite surprised. I have since sold that truck and bought a new one. Now my 1999 Suburban is leaking a few drops of oil onto the driveway and I'm thinking of using Mobil Drive Clean Plus. My dilemma is should I alternate between DC+ and a non-high mileage oil for...say...two drain intervals each or would it be safe to use DC+ for every oil change. Question: What, if anything, have you heard that might be negative regarding the prolonged use of motor oils that contain these seal swelling agents? Thanks in advance! [ January 11, 2004, 08:46 PM: Message edited by: cheeks ]
In terms of seal swell, just rmember that what goes up must come down. Swelling a radial seal means the inner lip diameter is pressed against the journal and this will wear the seal back. When the seal swell is removed, the inner lip diameter and/or face will then shrink. I would prefer to clean and condition a seal rather than swell it too much. How much will these oils swell a seal, who knows unless a test is made at operating temp.
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