Switching back and forth between oils

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268
Location
IL
Since my wife's '03 Honda Odyssey requires 5w-20 grade oil, I usually find myself not finding my preferred brand, Mobil 1 0w-20, and I end up buying Motorcraft 5w-20. Some many time I end up switching back and forth between Mobil 1 and Motorcraft oils. Motorcraft is a syn blend, as far as I know. Mobil 1 claims to be compatible with conventional oils, reason for which I haven't worried too much about it. Could this switching back and forth between oil brands/formulations eventually have an adverse effect on engine seals, for example?
 
Messages
575
Location
Wisconsin
I, personally, have never had any issues and most people here will agree with me. Some people here run synthetic in the winter and dino in the summer.
 
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13,132
Location
By Detroit
The oil in my wife's Aerostar by the time I got done with it included some of each of the following: Valvoline Durablend 5w30 Valvoline Maxlife 5w30 Citgo 10w40 Royal Purple 10w40 Rislone Engine Treatment Didn't seem to bother it a bit.
 

TC

Messages
1,644
Location
California
Good question, GimmeTorq. I found two bits of information on this: "What about solvency of Group II base oils? Is it true that formulations that use these stocks have problems with rubber seals swelling properly? While they do have slightly lower solvency than Group I base oils, ChevronTexaco Group II base oils exhibit a level of solvency compatible with the vast majority of additive components and systems. Furthermore, ChevronTexaco base oils have higher solvency than most synthetics. When properly formulated, lubricants made with ChevronTexaco base oils have proper seal swell characteristics." http://www.chevron.com/prodserv/BaseOils/faq_answers.shtml "MYTHS #4 -- You can't switch from synthetic oil to conventional oil or vice versa. You need to start with a synthetic blend for a few oil changes before moving to full synthetic oil. Once you start using synthetic motor oil you cannot go back to conventional oil. Synthetic and conventional engine oils can't be mixed, or else they react and cause engine problems." "FACT: As long as the synthetic motor oil product and conventional motor oil product meet the viscosity and performance requirements outlined in the vehicle’s owner’s manual, you may interchange them with each other." http://www.quakerstate.com/pages/carcare/whattoknow.asp I don't have a definitive answer here, but my interpretation of all this is that it doesn't really matter -- you should be able to switch back-and-forth all you want with no significant detriments, if any. Quaker State basically comes right out and says doing so isn't a problem, that as long as each differing oil meets the "performance requirements" [API "SL" typically], you're fine in regards to seal effect. But they do make the interesting comment of, "If the seals are in good condition, synthetic oils may be used in high-mileage engines." So this suggests that using syn in engines with WORN seals is NOT recommended..? A slightly different twist on Mobil 1's traditional claims. Note that this topic also addresses "high-mileage" oils since they often include additional seal swelling agents to compensate for worn seals. [ March 31, 2004, 03:18 AM: Message edited by: TC ]
 
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