[Hoyt]

Has anyone had any experience with changing brands of synthetic oil? I've been running Castrol 5W-30 and I'm thinking of changing to Penzoil 10W-30. I've heard people say that you should mix synthetic with conventional oil but is there any problem with mixing one brand of synthetic with another?

[Centerline]

None that I've ever heard of. I run only synthetics in all my vehicles and have never had a problem switching brands.

Centerline

[302 Z28]

If I remember correctly, Castrol (Syntec) is a blend, not 100% synthetic. There are no problems with switching, assuming your engine is in good condition. I have never heard that you should mix some conventional oil with the synthetic. What is this supposed to accomplish?

Vince

[Hoyt]

(I have never heard that you should mix some conventional oil with the synthetic. What is this supposed to accomplish?)

That was a mistake on my part, I meant to say you shouldn't mix them. Thanks for the input, I built this engine a few years back and it only has about 20k miles on it so I don't think the change in oil will greatly effect the performance of the engine, I was more concerned with the chemicals in the two oils being compatible.

[Cstraub]

You will be fine.

Chris

[Hoyt]

Thanks Chris, I thought so but I wanted to get the opinion of some trained professionals.

[68NovaSS]

Hmmm, I heard long ago, can't remember if it was a reliable source, that mixing synthetic with fossil oil was reasonable from a money standpoint - that one to two quarts of synthetic gave the protection benefits without the expense of using 100% and was an acceptable procedure. I'll try to find the reference and repost if I can find the answer.

[Croz]

Hmmm, I heard long ago, can't remember if it was a reliable source, that mixing synthetic with fossil oil was reasonable from a money standpoint - that one to two quarts of synthetic gave the protection benefits without the expense of using 100% and was an acceptable procedure. I'll try to find the reference and repost if I can find the answer.

Well, I read a book of an article a while back on the subject of motor oil... the good part about synthetic is that it is a uniform size in particles, where as petrolium based oils are a mixture of different sizes. So mixing a synthetic and a petroleum based just makes an expensive oil that is still not of uniform size. Thereby making synthetic blends and the such no more helpful than a petroleum based oil. I say if you are going to shell out and run synthetic, get a good one. Most of the good ones you can't even get at a place like O'Reilley's or AutoZone....

[Ghetto Jet]

302/Z28 Castrol Syntec is actually fully synthetic. Croz your right the best synthetic motor oils can't be bought at the local parts store. Check out AMSOIL's website, they have extensive tests on the site, they beat every synthetic brand you can buy at a parts store, Castrol, Mobile 1, Pennzoil, ect ect. and I believe they also have a test showing how their oil out did Red Line or Royal Purple, I can't remember which.

Mike

[302 Z28]

Mobil 1 was second in the test to Amsoil. The test I saw didn't even list Royal Purple. The fact is that Amsoil and Mobil 1 were so very close in performance it was meaningless. There was only about a ten or fifteen degree advantage Amsoil had on Mobil1 on the high temp test. That temp was far above what your seals and gaskets could withstand, so what is the point?

Vince

[68firebirdguy]

Go Royal Purple all the way. That stuff rocks! I use it and i wont go back!

[Ghetto Jet]

302/Z28, I couldn't find the original article I mentioned as it was separate from the tests you saw. I did find these two AMSOIL related articles though. http://www.performancemotoroil.com/Royal_Purple_info and http://www.performancemotoroil.com/Dyno_test

Vince I do agree with you, all synthetic oils have an order in which one is better than the other, but the differences are so minimal and the points at which some fade is well beyond the points an engine could ever go, so to the engine it really doesn't matter which synthetic you use. But personally, since they all cost pretty much the same, except Red Line, if I'm going to dish the extra money out for synthetic I'm would buy the one that does the best in the tests.


Mike

[87442lover]

In some articles they say to mix 4 parts regular with 1 part synthetic. Gives some of the benefits of runnings synthetics. Have found no problem doing this.

[302 Z28]

I would use Amsoil, if it were available at Auto Zone, or Advance Auto. I do use Amsoil air filters in my cars however, after reading the test that nailed K&N. Having to order the oil is a main pain, Mobil ! is readily available, as are their filters.

Vince

[chevy350]

DONT USE PENZOIL!!!!!!!!!!!!IT SUCKS/castrol,valvoline,roal purple only oils i trust,personally i run valvoline VR1 racing synthetic oil.the hydraulic lifters love it,dont know why?and it lasts