Quote Originally Posted by nfpgasmask
I am burning oil and need to add some, should I stick to 15w-50 or could I put 5W-30 in? Will it hurt to "mix" the two?
Mixing is fine, but to be safe stick to the same brand of oil. In the old days, there were certain oils that were bad to mix, supposedly because of differences in base crudes having chemical reactions. This could be an old wive's tale though. I've been broke and had to do it and never had any problems. In fact, I've purposely mixed oils to increase or decrease the thickness. My Jimmy had really low oil pressure after putting 10w30 Napa synthetic in it. I added some 20w50 Valvoline Synth somebody had given me and got it into acceptable range. It's not a good practice, but works in a pinch.