Is mobil1 5w-30 acceptable to use to add to factory fill?
 

Had to add 1.5qts M1 and 1 qt. castrol syntec 5w-30 in about 2K mi. The M1 isn't A3/B3 approved but it is API SJ. So WTF does that mean? The castrol is A3 approved. I don't think M1 is so great when their 0w-30 and 5w-30 isn't a3/b3 approved when many other syn makers are. The manual says these grades are ok but need to be A3/B3 or SJ. Is it and/or or just or approved?

My dealer used M1 5w-30 for my 5K service.

Re: Is mobil1 5w-30 acceptable to use to add to factory fill?
 

My dealer told me to use Mobile One 5-30 in my S4. That is what the dealer used on my 5K service.

Neil

M1 0W-40 meets all the qualifications you seek (only M1 oil to do this)
 

5W-30 will be just fine in your car.

Do you have an 04 or 05?
 

I have an 05 and service manager said M1 0-40 full synthetic. May be different for 04s.

5w-30 is fine. 0w-40 is the only M1 to carry the VW/Audi certification however.

LOL, sorry didn't see your post. Nice thinking BTW. ;-)

That's OK. I don't come around very often anymore, so feel free to ignore me. ;-))

I hate to be contrary, but..
 

There can be problems when adding one brand of synthetic to another brand of synthetic. Different viscosities of the same brand are usually fine.

It is actually safer to add dino oil to synthetic, unless you know you're adding the same brand/formulation.

If you want more info, read some of the very good oil FAQs out there on the net.

Re: I hate to be contrary, but..
 

The whole problem w/ that is that 05's are syn only and according to my service dept it's supposed to be M1 factory fill (they're probably wrong, though) so I don't know exactly which oil is in there. Also, the castrol says it can be mixed w/ petro or syn oil. So if the factory oil is M1 then everything is cool. If it's not M1 then chances are it's castrol 0w-30 and you can mix the M1 w/ it. Either way it's compatible, hopefully.