Nope...you just don't want to top off your regular (fossil fuel based) oil with a synthetic or the synthetic with a fossil fuel based. A complete change with a new filter is all that'* recommended when switching between blends.

Nope, if you use Seafoam according to directions, it will be a little watery coming out. Just let it all drain and reup with Synthetic.

ok thank you for all of your help, i plan on driving my baby till the wheels fall off, then im gonna out them back on till they fall back off

Use Mobile 1 synt. Change your oil and filter and other fluids and your engine will last.

shud i get any specific oil, like high mileage or something like that or just normal Mobil synthetic oil?

Use a 5-30W or a 10-30W or whatever your owners manual recommends.

Personally, I have used Zmax in one of my cars and I have no complaints. I had a 1980 Chevrolet Citation X-11 that got at the most 10 MPG. After putting in the Zmax additive, I found that the fuel economy jumped from 10 to 14. So, I really have no complaints. I actually thought on using this additive in my Riviera.

so what your saying is that it cant hurt to use zmax?

I would say it wont hurt anything. But I'm thinking it wont help any either. Like I said earlier, you can't beat a good oil changed regularly. And if there is damage, nothing in a bottle is going to fix it.

If you have some minimal leaks or lost compression, high mileage oil might help a little. Additives like gasket conditioners can soften cracked ones enough to stop drips (but there'* no sure guarantee of that. But remember the softening part. If your gaskets are intact and not leaking, why soften them and risk it causing a leak that isn't there. Additive'* that clean the engine aren't needed if your use a predump cleaner. Why have an oil that works on sludge deposits therefore fouling it quicker, the last thing you need is sludge freed by such getting between your crank and sleeves. Possibly clogging old dirty oil passages. If it isn't broke then don't try to fix it, and if it is broke, fix it. Anything in a can uses things that at best slow a specific problem, and as well may hurt in another area.