I have heard in the past that to switch between the two will cause various seals to expand and contract which is not good and the blended stuff, I would stay away from it, just choose one, preferable 100% synthetic, it lasts longer and is nicer to your car. Remember just because a company provides it doesn't mean it is good...

 

Great!! Now I have to know which Brand it was exactly ? Label on my Castrols say that synthetic and conventionals are "compatible." I guess that means it's ok to mix the two...anybody work at Castrol ? Why is synthetic better than the conventional? I know I'm making fuss of nothing but just want to make sure what I'm putting into my baby . BTW it's funny I don't remember going through this grief when I had my Prelude (not that lude is a bad car) . Thanks guys.

 

Dude, don't sweat it! You're just topping off! For that purpose any SJ or SL oil is fine.

When they say "don't mix" they mean don't use the leftover 1-1/2 quarts of 5-30 Pennzoil conventional from your Civic six months ago with the 2 new quarts of Mobil 1 synthetic 10-30 you just bought and the quart of Castrol Syn-Blend 20-50 your ol' college buddy gave you last year...

Sheesh...

 

When I bought my 328 it didn't come with synthetic oil...

 

ok thanks guys. I just put about 1/8 QT of Castrol GTX (conventional) this morning...every one clap . I wasn't really sure about how reliable my oil level readings were. Everytime I dip the stick and pull it out I would get different readings. Just this morning, one side of the dip stick read 1 notch above L and on the other side I saw 3 notches ...wipped it off and dipped it again....same result! May have to do with the oil being cold and too viscous (looks a lot darker in color as well)? Or could be I actually started motor and then turned it off to check the oil level spewing the oil all over inside messing up my reading?
So I ended up just putting "little."

 

About the BMW and M-B thing, I am not sure, although I am pretty sure that my mother's Benz did come with synthetic, because I called up to see why the first oil change was after 10,000 miles. About BMW, I just thought I had heard from my friend with an M3 that his beemer came with it too, sorry about that if I was wrong althought the M series may be different.

 

[QUOTE]Originally posted by Destiny2002
[B]Doesn't matter.

 

One side of the dipstick almost always reads lower -- the engine block is tilted! Use the lowest reading.

Mobil1's web site lists the cars for which it is the factory fill.