changing to synthetic

[SLS]

I will be changing to synthetic 2-cycle oil in my merc. 175efi this year. What I need to know is, can I add the synthetic oil to the reserve when the level gets low with the remainder of the petroleum based oil in the system, or could this cause a problem in some way? Thanks in advance.
SLS

[Walleye Daddy]

You cannot mix the two. You must completely get all the petrolium out of the system before you even think about putting synthetic in. I wouldn't switch. Stay with the good old petrolium, we have all been using it since before we were born without any problems. Also, once you switch, you can't switch back, all the seals in your motor will go to heck.

Good Luck,
Walleye Daddy

[Sparky]

I have a Mercury 175 outboard and switched to synthetic oil three seasons ago. It's the best thing that I've done for my motor. I occasionally have the cylinders checked for carbon buildup and this problem went away. The 2 stroke smoking was substantially reduced. The manufacturer said that I didn't need to empty my reservoir. The two oils are supposed to mix OK but, I emptied my reservoir and then refilled it with the synthetic. I just saved the old oil and eventually gave it to a friend who was still using petroleum based oil. From all of the research I've done the synthetic oil is a superior product. As much as a V6 outboard costs I consider it cheap insurance.

Sparky

[Walleyefisher]

Absolutely, you can mix the two together. I use a penzoil blend that is both synthetic and petroleum based. I would burn the petro based oil up and then switch over, but you don't have to.


Good luck and Good fishing

[s-bone]

I just purchased new 60hp 2 stroke and I am going to start it out on synthetic. mercury has it out now. when I asked the service manager about switching my other motor to synthetic he told me just run it low and dump it in. It won't hurt it to mix it.

[Dave in Mpls]

s-bone...

You may want to rethink that. My understanding is that a motor should be broken in using a petroleum based oil. The synthetics lubricate so well that the rings and cylinder walls don't get to break in properly.

Regards

[Sparky]

I agree with Dave. Break the motor in with petroleum based oil and when the rings are seated well switch to the synthetic. I also dothis with my vehicles and if they weren't using oil at 10,000 miles they won't be using oil at 1000,000 miles.

Sparky

[moptop]

As long as the two oils have the API "starburst", the can be mixed without any worry of being incompatable.

[s-bone]

thanks for the warning, I pick the boat in mid march and will find out. I think I will follow your advice and break it in and then switch.