Mixing Motor Oil

It is poor practice to do this, but it shouldn't cause any problem as long
as the residual oil is clean, dry, and of the required
viscosity and class.

Then why is it poor practice?

Thanks for all the input.  I will stick to the advice of not mixing
different weights of oil.

Thanks for all the input.  I will stick to the advice of not mixing
different weights of oil.

***Probably the best scenario, BUT the reasons for not
mixing weights are few, at best.   Weights are viscosities,
nothing more.   If you are within the viscosity range for
the temperature, and if your oil is clean and has the proper
additives for the service you are running, there is no big deal.

I dont mix them, BUT my car requires 6 quarts, plus 3 ounces
of oil.  I keep a bottle of oil from which the 3 ounces can be
made up.  Then I add 6 quarts of oil per change, and top up
with the odd bottle.

This is not rocket science.  

Why not just buy two 5-qt jugs, and save the remainder for the next
oil change?

I'm actually now in a similar situation as the Original Poster.  Just
sold my '96 Camry, which takes 10W-30.  Our '99 and our Sienna take
5W-30.  I'm slowly using my remaining 2 quarts or so just topping off
the oil as needed.  It's all Mobil Clean 5000 anyway.

Why not just buy two 5-qt jugs, and save the remainder for the next
oil change?
*******
I dont know if that would be any cheaper or not...Maybe,
if you dont buy any quart size oil at all. My Solara requires
5 quarts, but the Avalon requires 6 quarts plus a little.

The only times I've paid attention to sales here were a couple times
they had an oil filter and 4 quarts of oil for sale at a very good
price, and they gave customers the choice of a one-gallon bottle or 4
one-quart bottles, same price.