Changing up brands of 2 stroke oils question

[gmacp]

I am presently running the Shell advance 2T regular 2 stroke oil, and changing to Polaris blue synthetic oil. Is it necessary to drain the oil tank of the old oil, before filling with the new oil. I have read that mixing oils can cause problems.

 

[gmacp]

I mixed the 2 oils together in a small plastic container, no visible changes in the first 15 minutes. I know that that doesn't really mean much.They are both blue in color and mixed easily. Not sure on what's next, any help would be greatly appreciated.

 

[turboless terry]

I have done it a bunch and never had a problem. I always ran it down a little but the last time i didn't and never had a problem. You already did more than i ever did and there is no visible change so go for it.

 

[BeartoothBaron]

I think the only reason people talk about that is some 2S oils don't mix well. I recently started using Castrol 2T snowmobile (yup, went the other way with synthetic), and you could see it form a layer with the Poo VES oil I'd been running when I first poured it in. I've never heard of mixing oils and having some reaction between them, but some still suggest running the tank down to 1/4 or so. I can't say I see even a reason for that: as long as it gets oil, it doesn't matter if it's the old stuff, new stuff, or a mix of the two.

 

[jcjc1]

seems like if mixing oils was an issue then it would be explicitly stated in the owner's manual.

 

[gmacp]

I am going to remove as much of the old oil and top up with the new. Thank you for your replies, sure makes the decision easier with all of the knowledge and experience of the people on this site.
I recently bought the Polaris maintenance manual, what a disappointment. It is almost as vague as the owners manual. Thanks again for those who replied.

 

[FlynHigh]

I bought a used oil tank and in the bottom of it was some rather large wax pieces that I assume came from mixing different oils. I didn't notice it till I got home and don't know the history of what oil was used in the tank previously but obviously something reacted between different oils. I remember 20 years ago when I was into dirt bikes it was well known not to mix castor oil with other oils.