I don't think this is a problem but would like to get some opinions on it. I have been using 5W30 in my Jetta Wagon (2.0 gasoline engine) for quite some time and I have some extra oil still in the garage. I recently thought I should move to the 10W30 oil to quell some of the lifter noise and reduce some of the oil consumption. It was recommended on this site to go for some 5W40 oil and that is in fact what the owner's manual recommends although it says 5W30 is a suitable replacement. Well, finding an inexpensive 5W40 oil is no easy task but I was able to get a really good deal on some 10W40 so....I was thinking mix in a little 10W40 with the 5W30 I already have on hand and maybe that will give me something similar to a 5W40?? Is there any problem with mixing oil of different weights?