Mixing viscosities???

[901Memphis]

Maybe in an engine that shears viscosity rapidly you would want to top off with a higher grade to bring the viscosity up a little. Such as topping off a Nissan vq with 5w40.

Redline recommends mixing to achieve products that aren't available directly.

The specs on the caterham blend are truly awesome. Just need more uoa to go with it.

 

[Errtt]

Some years back I used to mix some synthetic with conventional. Older pushrod v8s and never had an oil related issue.

 

[KCJeep]

I like to blend for my Jeep. Off the shelf thickish 30 grades with a VI higher than common in 10w30's don't exactly grow on trees. But blends of 5w20's, 5w30's and 10w40's will get me there easily.

I am currently running 5 quarts PYB 10w40 and 1 quart 5w20 PYB for example, which gives me a very thin 40 which will likely shear to a thick 30 by the end of the OCI. Perfect!

 

[Garak]

Originally Posted By: NormanBuntz
Every one stated to only add oil of the same viscosity. So why mix during a refill, aren't there enough multi-grades available out of the bottle?

I agree with you on the latter point, but but some people do mix in a well reasoned fashion. I don't do it, but that doesn't mean it can't be done.

With respect to the first point, remember the target audience. The automakers are trying to ensure that you're using oil of the specified viscosity or viscosities. Topping up your sump of 5w30 with a quart of 10w30 isn't a big deal (although it would bug me to no end). However, tossing a litre or two of straight 50 into a 0w-20 sump would be far less advisable, in my view.

Others have brought up CATERHAM. He likes to blend. I give him a hard time about it in a friendly fashion all the time. When he finds this, I'm going to bet that you will, in retrospect, wish that Bill had locked the thread.

@Shannow: I have actually seen the recommendation, but as you know, we in North America tend to get spoon fed a single viscosity recommendation, and have been for years. Maybe next year, Toyota will require that oil changes only be done in shops that have no 30 or 40 grade products inside, kind of like the peanut allergy thing.

 

[901Memphis]

Topping up one grade higher will typically result in better viscosity at UOA time. The exception i think to this is when you run super extended drains the oil actually can thicken from other factors. So topping off 5w20 with 5w30 and topping off 5w30 with 5w40 could be beneficial in some applications.

I think its a good idea to mix similar additive packs though, i don't like to mix sodium additive packs with the high calicum/boron blends. Theres only a few that use Sodium like Valvoline/Napa, Lukeoil, Schaeffer's, Lucas, and RP.


I think adding one of these types of oils can dilute the high calcium you find in Sopus products and many other top brands .