I need to do an oil change on my car & it does burn oil sometimes (especially at weird times). A friend I have that is car knowledgeable says to use thicker oil & I do put 10w30 in the summer. But, being on the cheap with the price of oil through the roof these days, I only have 3 bottles of Shell dino 10w30 left. So, I wanted to know your opinions if I can do this combo of 3 x 1L 10w30, 1 x 1L 5w30 & the rest (about .7L) of Motomaster 15w40 Diesel oil? Now, I have been topping up with the diesel oil & haven't had any problems, but one of my friends told me that diesel has some additives that may be diesel specific, thus the reasons I'm asking. Oh, & I'm just waiting for Costco to put the Shell oil on sale then I'll buy 2 cases. I bought more 5w30, but I used my last stock of XD-3 for this past oil change from January.