Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Mixing Synthetic Oil Brands

Recommended Posts

I took my wife's car (not a Porsche) to the dealer the other day to have some maintenance done. I asked them to use synthetic oil, and they used Amzoil. If I need to add some before the next oil change, can I just add some Castrol sythetic or Mobil One of the same viscosity?

Link to comment
Share on other sites

They used Amzoil.  If I need to add some before the next oil change, can I just add some Castrol sythetic or Mobil One of the same viscosity?


It is far preferable to use the same brand and type of oil. Porsche says:


The engine oils approved by Porsche can be mixed to the extent that it is not necessary to flush the engine when the oil is changed, or another type of oil is used. This holds true for mineral oils and synthetic oils.

However, since every brand of oil has a specifically adapted unique composition, the same oil should be used for any topping up that might be necessary between change intervals, whenever possible."

Basically, if you mix two oils the oil manufacturers have to make sure that the resulting mixture does not turn into some sticky goo. However, each band has its own additive package, and for optimum performance they should not be mixed.

Incidentally, this even true within a brand. For instance, Castrol has hydrocrack (group III) based "synthetic" oils and Polyalphaolefine (group IV) based "synthetic" oils. My understanding is that the PAO-based oils use a different additive package, so for best performance the two should not be mixed.



Link to comment
Share on other sites

Thanks for the useful info. In general, I haven't had to add any oil in between oil changes, which I have done once a year (which is usually 5.5k - 6k miles). But in case I do, I guess I should hunt around for this Amzoil (which I've never come across).

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.