Can you mix synthetic oil with regular oil?

[RVthere]

I gave my truck an oil change yesterday and somehow managed to overlook exactly how much oil I had on hand. I had nearly half of what I needed of synthetic and then the rest of was 10W-30. For the sake of time, plus it was nearly 10pm, I just went for it.

I'm having one of those 'did I screw up moments' and wondering if this was OK to do?

 

[smritte]

Your good.
The difference between the two is the quality of additives and the purity of the oil.
Synthetic oil is still oil.

 

[Derek]

Interesting, never really thought about this. But then again, I have never tried mixing. So does this mean you get the best of both worlds?

 

[smritte]

Actually just the opposite.
Regular oil is poorly filtered, has a ton of impurities in it and poor quality additives. These shorten its life span. Its not an issue if you change it often enough. Synthetic oil is chemically purified with a better additive package. No impurities.
By mixing, the regular oil will still break down fast. You need to change it ant the normal time for regular oil.

Heres something people don't know. Semi synthetic is regular oil with just a tiny bit of synthetic oil mixed in. There's no laws about how much synthetic has to be in there. The oil companies mix in a little synthetic and raise the price. Total scam. Basically you have what the OP questioned here.

Pennzoil is one of my works sponsor's. They send a couple of engineers down once in a while and do seminars. Very enlightening.