switching brands

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Oct 30, 2005
South Dakota
My wife's brother and dad say "Never switch brands or weights of oil. It will cause your vehicle to use oil.". Where does this myth come from?
I say switching brands is no problems. As far as weights, I say if you have always run one weight of oil, this might be true. If you are used to switching to a lighter weight for winter and have done so, there should be no problems.
I figure most of the myths probably come from the old days when vehicles and oils were different than what they are today. Just like the myth of the 3K oil change. Any thoughts? [email protected]
Well I am not sure that changing brands is good or bad. I tend to stay with one brand, but I have also seen people change brands like they change dish water. In the end I guess it's not an issue.

I ran Quaker State for years until they had QC problems in the late 70's, then I ran Castrol GTX up until a couple of years ago, except for a 3 year run on Valvoline AC, then I started using Amsoil on everything.

I guess additive clash is a thing of the past so changing brands every OCI won't hurt a thing.
There is an actual observable phenomenon sometimes when you switch brands. For a period of time, sometimes a couple of changes, consumption may increase. There is a theory that a different additive mix causes one chemistry on engine parts to shed and another to replace it. The term used to describe this is "seating". Again, it's the theoretical explanation for something that is seen once in awhile.

Another issue that arises is a more detergent oil replacing a less detergent oil, or an oil that causes a bit less seal swell replacing an oil that swells seals more. In both cases you may get some leakage, either for awhile or permanently. Either the gunk holding the oil dissolves, or the seals shrink.

These days both of these are uncommon but not unknown.

The biggest problem with changing brands around is that if you're doing oil analyses you can't get any sort of baseline. It's the changes from baseline that are meaningful in oil analyses, and you can't get a baseline if the additives are changing all the time.

So, generally changing brands is not a problem, nor is changing viscosities, if you use a good quality modern motor oil. Lots of people run cars for years to high mileages using whatever API rated motor oil in the weight they prefer that's on sale when they change it.

So far on my 05 Corolla I've run the following;

OEM oil to 1k

Pennzoil to 3k

Castrol Syntec Blend for 5k

Castol blend + Syntec for 5k

Mobil Drive Clean Plus for 3k

Mobil 1 for 5k

Castrol GTX for 4k

Castrol Syntec for 5k

And right now Castrol Blend + Syntec + GTX for 5k.

I've had UOAs done on most of the changes and with the exception of a iron spike after the Mobil 1 to GTX, all have been fine and the engine is fine. All other metals have been the same.

And when I run out of my Castrol stash I'll be going to Chevron, Havoline and Pennzoil in it.

My truck has seen Mobil 1, Mobil 7500, Pennzoil, Chevron and QS with no problems in 6 years.

Not a problem IMO..

Take care, Bill
My Elantra has had OEM fill, SJ Penzoil 5w-30, Mobil DC 10w-40, Castrol Syntec 0w-30, Royal Purple 10w-30, Mobil 1 0w-30, and now Havoline Synthetic 10w-30. Next 8 oil changes will be Mobil 1 15w-50 EP mixed 3/1 with Mobil 1 0w-30, and then back to Syntec 0w-30 (Green GC) for probably the rest of the cars life.
Other vehicles I have had before this have been whatever was on sale at the time and never knew of any problems with switching brands.

Now if trying to find a real trend with UOA's, then you should probably stick with one brand/weight.
I'm a little nutty in that I have for a long time deliberately switched brands. The theory is that every oil's add pack has its strengths and weaknesses. If I switch around, no particular engine contaminant will be able to build up (which might be the case if I used one oil for a long time that happened to be weak on that contaminant).

Since finding BITOG, I have more info on the oils, though. So my switching may be limited to a smaller set of brands. I think some oils may be weaker on all types of contamination.

(Sometimes I do this with gasoline, too, but only if the prices are equal.)
Changing brand may cause your non-user to become a user. Different base stocks & different add-packs can do that.

If you presently have a non-user & your engine is quiet & clean.... don't change a thing.
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