Yes, I've searched the FAQs! It says "once synthetic oil has been used, its best not to switch back to Dino oil". Anybody know why? (my daughter had the oil changed in her 99 RX300 yesterday and they put dino oil in it - it's had synthetic every time since the first oil change).

Thanks

 

synthetic oil and conventional oil dont mix well. they will separate. otherwise if u want to switch. make sure u keep using conventional oil. dont keep mixing syn then conventional. could cause problems

 

Myth is that rubber seals will swell up.

Fact or fiction?

If you cant mix, then why are belnds sold?

salim

 

Exactly what I'm wondering. What is a blend then?

I suspect the whole "don't mix" :"don't switch back and forth" thing is a myth. I wish somone could show conclusive evidence by someone who actually works in the business... and I DON'T mean Jiffy Lube or a dealer. I mean you're a chemical petroleum engineer for Valvoline or something.