Changing to Synthetic Oil

I'm thinking very seriously about changing to either full synthetic or syn blend on my 1987 90hp Mercury. Do I need to drain the remaining oil from the oil reservoir or is it ok to add the synthetic in with the mineral oil that is still in the supply tank?

Jayhawkokie
Grand Lake OK

Re: Changing to Synthetic Oil

I think Amisol (spelling?) advertises no mixing with paraffins, but all others that I have seen of any type/brand clearly specify that they are compatible. I think the reason for the Amisol position is the way they determine the life cycle of their oil. Having any other oil in the formula would skew the results.

Mark.

Re: Changing to Synthetic Oil

Follow the mfg directions on bottle, if your using a blend just add it and go.

Re: Changing to Synthetic Oil

When I owned 2 strokes, I used Pennzoil semi synthetic and it could be mixed with dino oil with no problem. You can also use synthetic in your lower unit.
Since my 4 strokes are way out of warranty, I converted them to synthetic the weekend I bought them. I have always used Castrol, recommended for my old triumps/mg's. When they came out with synthetic many years ago, I started changing as I did my rebuilds. So, I used Castrol Syntec with my 4 strokes. I gained 200 rpm wot after the change...I kinda like the stuff...

Re: Changing to Synthetic Oil

Just to warn you, there is some controversy over Synthetic blends and pure Synthetics. Lot's of negatives on the pures syn's in two strokes but lots of kudo's for the smokeless syn blends. The syn blends will mix with your current blend no problem. I break my motors in on Merc Blend at 40:1 and then ween them off to Penzoil syn blend at 50:1

Re: Changing to Synthetic Oil

Re: Changing to Synthetic Oil

jeffnick said:

Do you like to gamble?
What do you expect to gain by switching?​

Click to expand...

I waited for a long time when Syn's came out before stepping up to the plate. Probably what convinced me was the use of Polyalphaolephins where I worked. I got interested in them and when I learned that this is the key ingredient of syn oils used in the transportation industry (plus detergents and other additives engines require), I got that much more interested.

That was 10 years ago and all my stuff is syn today including gear lubes which comes standard in my Dodge truck tranny and differential. Also higher priced auto's come standard with it from the dealer in the crankcase.

On blends, one would have to ask "just what is a blend". Well sir, it seems to me that you put some of old dino in and some poly in, stir em up, you get (some of the) benefits of the poly without having to pay full poly price. So adding syn to a pre-existing dino oil sump is merely blending oils. That's the way it looks from here.

My 2c,

Mark