Castrol's view on mixing oils

[aa1986]

I sent an email to Castrol asking about mixing grades within the same brand and also mixing across their brands.

In short, the only thing they say is ok in terms of mixing, is topping off with the same grade of oil. If you do this a lot, make sure it's the same formulation. Anything else in terms of topping off and mixing is not recommended. Here are the key points of the reply I got:

- For topping off: You can use any of their products / formulations so long as it is the same grade. They do not recommend topping off with another grade.

- They do not recommend topping off with a different formulation on a continuing basis.

- Do not recommend mixing different grades even in the same formulation.

- Do not recommend mixing formulations due to changes in viscosity that can develop. (This is something Shannow pointed out).

- They said that Edge gold bottle with Titanium FST is not the same as the Edge gold bottle extended performance.

 

[jacky]

i have always topped off with the cheapest oil i can find
i usually buy thicker oil because i have a severe leak
on occasion i have used straight 30 wt but i know better now

 

[jrmason]

And what are the consequences? There is enough oil left in an engine during an oil change to tell me absolutely nothing will happen when/if you decide change oil types or viscosities.

 

[gfh77665]

There are roughly 3.417 Gazillion anecdotal experiences around the globe that prove otherwise.

 

[Clevy]

Originally Posted By: gfh77665
There are roughly 3.417 Gazillion anecdotal experiences around the globe that prove otherwise.




Pretty much.


I mix oils just about every single time. Engines are spotless through the fill hole with 10000 mile intervals.

I don't expect any oil blender to say go ahead and mix grades and brands. It's not in their best interest from a marketing point of view.
If I wanted to sell oil I'd tell customers they can mix anything and to only buy the grade required.

 

[surfstar]

I'd reply saying that I will no longer be using Castrol, since other companies state that mixing is fine (along with the API itself).

 

[HTSS_TR]

Castrol wants to scare drivers in using other brands/types so they can sell more. This is not good in term of marketing.

According to them my 1994 LS400 engine should be out of service long time ago because it almost never had more than 2 OCI's with same brand and/or type. But its engine is running great after 370k miles.

 

[Eddie]

Same recommendation from M1 and Pennzoil. Not following their recommendation for 10 millionth time and no problem but, I don't want to be the one in 10 M that has the problem.

 

[OVERKILL]

Originally Posted By: surfstar
I'd reply saying that I will no longer be using Castrol, since other companies state that mixing is fine (along with the API itself).



The API "mixing" spec only requires, as Shannow has pointed out countless times, that the oil won't turn into Eggnog. It does not, in any way mean that the oil will retain its viscosity characteristics, particularly low temp performance, nor continue to meet the performance specifications it is approved against.

 

[mongo161]

I've mixed, and continue to blend, different grades, formulations within the same family. I've run Castrol Syntec, black gallon jug compliments of the Kmart clearance, with Castrol WB and also with Castrol Synblend. In fact some of my neighbors vehicles, that I change the oil on, are now running a blend of Castrol Synblend 5w20 and Castrol Syntec, black gallon jug, 5w30 for the cold winter months.

IMO...the major oil companies don't like you to mix oils because they need you to go buy more of the same grade, family and formulation. Then name of the game is Sales. Synblend by Castrol is a blend of Edge black bottle/Gold bottle with Castrol conventional WB. The percentage of synthetic to convention is a big secret......why??? is a better question for Castrol.

 

[wemay]

http://castrolmagnatec.com.au/faqs.php


WILL CASTROL OIL MIX WITH THE CURRENT OIL I AM USING?-

Castrol MAGNATEC is designed to mix completely with other synthetic, part synthetic or mineral lubricants. Not only is it perfectly okay to top up your vehicle with Castrol MAGNATEC, you will begin to benefit straight away from the protection of its Intelligent Molecules which reduce the engine wear that would occur with inferior oils. To reap the full benefits of Castrol MAGNATEC, a complete change of oil is recommended.

 

[OneEyeJack]

Instead of worrying about the details you could just stick with the same exact oil and only top off with something else if it becomes necessary. There might be factors involved in the formulation of your oil that you may know know or understand that would not be used for some reasonable reason in the oil you choose for a mix. I don't think the issue is damage but might be more correctly characterized as reduced performance.

 

[Clevy]

Originally Posted By: wemay
http://castrolmagnatec.com.au/faqs.php


WILL CASTROL OIL MIX WITH THE CURRENT OIL I AM USING?-

Castrol MAGNATEC is designed to mix completely with other synthetic, part synthetic or mineral lubricants. Not only is it perfectly okay to top up your vehicle with Castrol MAGNATEC, you will begin to benefit straight away from the protection of its Intelligent Molecules which reduce the engine wear that would occur with inferior oils. To reap the full benefits of Castrol MAGNATEC, a complete change of oil is recommended.



So we've got Castrol talking out of both sides of its mouth at the same time.
At least mobil sticks with one story.............

 

[Powerglide]

Mix away. The motor will still outlast the rest of the vehicle.

 

[aa1986]

Originally Posted By: OneEyeJack
Instead of worrying about the details you could just stick with the same exact oil and only top off with something else if it becomes necessary. There might be factors involved in the formulation of your oil that you may know know or understand that would not be used for some reasonable reason in the oil you choose for a mix. I don't think the issue is damage but might be more correctly characterized as reduced performance.


You've hit the nail on the head. It isn't that damage will occur, it is that the performance of the oil cannot be predicted or guaranteed. If they said mix away and you weren't happy with the results, then they open themselves up to unhappy customers.

On modern vehicles with much longer ocis than before, as well as on engines that require oils with higher manufacturer specifications (I am thinking Euro cars mainly), there is probably a bigger risk from mixing than for older vehicles where modern oils are far better than required.

Originally Posted By: Castrol North America customer service email
Each grade and formulation has been specially formulated in a manner to which you can expect maximum performance


which suggests that if you tinker with it, you may not get maximum performance. Indeed, you may get "adequate" performance which none of us want right?

 

[Doog]

I only top off with "open and on the shelf" brand oil.

Not sure if this is harmful but I have been doing it since 1968 on about 40 different engines. Never had a failure.

I will try for another 20-25 years and report back.....

 

[wemay]

VALVOLINE:

http://www.valvoline.com/faqs/motor-oil/full-synthetic-motor-oil/

Can you mix different types of motor oil? For example, synthetic and synthetic blend or regular and synthetic? Is this going to cause problems?

Mixing synthetic and conventional oils will not cause any problems. The oils are compatible with each other.

 

[wemay]

Mobil1:

http://m.mobil1.com.sg/products/faq

Can different synthetic engine oils be mixed together?

Mobil 1 is fully compatible with conventional engine oils, semi-synthetic engine oils and other synthetic engine oils if you need to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way.

 

[Shannow]

Actually Clevy, I don't see the two as being incongruent..

Mixing is mixing, they are safe, and won't split/clump whatever...that's what the standard is. It's not any guarantee of anything other than that.

I had a dinner back in my turbine days with a chemist from Castrol who was working on Magnatec.

Their test regime was
* Flush oil
* Reference Oil (Mobil 1 50 - think it was 5W, could have been 15W - yes Castrol's testing).
* Flush oil
* Test oil (with Magnatec)
* Flush oil
* Reference Oil.

Standard type of test, where they keep the reference and the test separated through a flush oil, and bracket the test oil with a reference.

He stated that post magnatec, both the flush oil and reference oil showed improvements due to the clingy "magnatec" (ester type stuff), laid down, that wasn't flushed off...

Anyway, the Standard only promises what it promises, which is why I'm swayed to not mixing anymore, and this idea if you need to have a top-up oil....SAE30 moewr oil. Plain zinc based additive, no VIIs, PPDs, or any of the other parts that MAY decide not to play nicely.

 

[Shannow]

Penrite when I spoke to their tech people stated also that their oils were all compatible.

They recommended mixing their "Race" range of oils to get exactly what you wanted, but cautioned against blending across the ranges.