Mixing Mobil 1 0w-40 & Castrol 0w-40

[randomhero439]

Hello - I am a long time user of Mobil 1 0w-40 in my '08 BMW 335i and '10 Mercedes GLK. It is convenient that both cars use the same oil... until recently. Many are aware that the new M1 FS 0w-40 is not BMW LL-01 approved anymore. I have about 4 quarts left of the old M1 0w-40 formula (not enough for a full oil change).

Castrol 0w-40 is at my local WM for $23/5qt. Is it OK to buy a jug of Castrol 0w-40 and mix it with the old formula Mobil 1 0w-40 on my next oil change on the BMW? I would switch both cars over to Castrol 0w-40 then.

Thanks

 

[Quattro Pete]

There are bottles of old M1 (pre FS) still available on the shelves of various local retailers. What's your bmw's sump capacity? 7 quarts? Just buy 3 bottles so that you have enough for one oil change.

Personally I'm no fan of mixing, but if you have to, it's not going to kill your engine.

 

[randomhero439]

Originally Posted By: Quattro Pete
There are bottles of old M1 (pre FS) still available on the shelves of various local retailers. What's your bmw's sump capacity? 7 quarts? Just buy 3 bottles so that you have enough for one oil change.

Personally I'm no fan of mixing, but if you have to, it's not going to kill your engine.



Ah great idea - those dont seem to fly off the shelf as fast as the jugs.

 

[kschachn]

From what I've seen about the "new" M1 0W-40, I'd rather mix that with the old for now, before you transition to Castrol.

 

[mazdamonky]

I would just go with the mixing. If you are using 5 quarts Castrol 2 quarts Mobil, it isn't a big mix, hardly any different than topping off with a different oil. What size is your sump?

 

[dareo]

If you do an OCI with one brand and change to another brand next time you will still have residual oil of the first brand in your engine. Essentially some mixing happens no matter what you do. I wouldn't worry about mixing the exact same 0w40 weights of different brands.

 

[440Magnum]

I'd just keep using M1. I've seen absolutely nothing to indicate that the "new" formula is in any way inferior to the old. I have no idea why they dropped the LL-01 spec, but its an 8 year old car anyway. All the specs it originally required will disappear eventually, replaced by newer better ones met by newer and better oils.