no, i don't mean coolant mixing with my oil.

i'm changing to synthetic this weekend, but was only able to get my hands on 4 quarts of my favorite synthetic (redline) in 10w30. i got 2 more of 5w30, planning to mix one of those in if necessary.

any problems with this? should i pre-mix or just dump the 5w30 in last, assuming it will mix around in the crankcase.

the weather here is quite mild, won't get below 45 or above 75 anytime on this batch of oil, but i do plan on hitting the track soon.

 

No schwett man! Put in all you got of the 10W30, then put in the 5W30. It'll mix just fine.

 

that's what i thought, thanks.

 

What about the opposite? mixing BRANDS of oil but not viscosity?

My $tealer filled the car at the last inspection with BP 10W-40 oil, but I can't find any BP stations around here, so I dumped in Mobil 10W-40 once when oil was low.

Then a few months later oil was low again, so I dumped in 0W-40 Shell after not finding any mobil or BP oil in any gas station following a long search.

I'm going to go with Mobil oil for the next oil change. The only full synthetic formula they sell here in Germany is 0W-40 however.

 

As long the API rating is the same or higher, I see no problems arising but for this car, I just "feel" better if I have the same brand oil in it. I some of my past beater cars, I didn't care and those cars didn't seem to care either.