I am about a quart low on oil and use mobile1 synthetic 5-30. I don't have any mobile 1 laying around but have access to a quart of Pennzoil full synthetic 5-30. Since I am going to change the oil in a couple of weeks, is it safe to add the Pennzoil to the Mobile 1 in my car? I would think so because they are both full synthetic and identical weight. Any thoughts?

 

I'm sure that other members will chime in, but I dont see anything wrong with doing that esp. if you are going with the same SAE weight and both are synthetic....

 

I wouldn't make a habit of it, but it won't hurt anything. Different companies use different additives, so the mixing of them could possibly cause a problem, but it's likely it won't. If there was really a risk there would be heaps of warnings about mixing oils. Mixing Syn and mineral oil, now that's a bad idea.

 

I've done it before many times in my RX300. Though I like to keep the same weight whenever possible. I have even done some blends of different oils and different weights (I had other reasons for doing this), but don't fret about what you did.

 

Tell me more. (And I read most of what you have in your link . . .)

If mixing is a bad idea, why are "Synthetic Blends" offered?

Synthetic oil is manufactured from dino, from what I've read. (Can't cite sources. That was from magazine articles, years ago!)

Also, if mixing is a bad idea, why would anyone (namely me) just switch the family mini-van from 5w-30 dino to 5w-30 full synthetic? There has got to be 'some' dino oil still inside the engine.
And this MOPAR engine is a lot quieter with synthetic and there has been no 'using' of oil since the swap to synthetic, in 1,000 miles.

I know of only one manufacturer that is shipping new vehicles (Corvette) with synthetic oil in the crankcase. (Granted, that was 2006 when GM did this.)

Please enlighten me.