Not in normal driving.
yes you can synthetic oil can go in any engine
Lucas also makes a synthetic engine oil additive.. Yes.
Yes, you can. It is even sold as a Synthetic Blend.
No, old oil can use synthetic engines
I use synthetic oil in my 2002 PT Cruiser, and it runs great! Synthetic costs a little more, but it actually better for your engine.
If your engine leaks oil, no you should not use synthetic oil because it will clean sludge and can make the leak worse. If your engine does not leak oil, I would highly recomend using synthetic oil(Pennzoil Ultra 10W30 from Walmart is a good and pretty cheap choice). As long as your engine does not leak oil using synthetic oil is a great choice regardless of how old it is.
Yes, you can mix them.
If you have kept regular oil changes, no prep is required. Just go and put the synthetic oil in.
No, I would not recommend using synthetic in an engine this old. Use a good 10w40 conventional oil.
if it's a turbo engine you should only use synthetic oil only!! if it's a non-turbo engine a conven. oil will do.
Yes.
Yes you can use a synthetic blend or 100% synthetic.