yes it can... get royal purple it adds up to 15% of your stock horsepower
Yes, you can mix them.
Yes, without any issues. That's what synthetic blend oils are (better than conventional oil, not quite as good as pure synthetic).
No. It will ruin an engine. The above answer is 100% wrong. You can mix convention oil with synthetic and it will do no harm at all. When you see them selling Synthetic blend that is what you are buying. A blend of synthetic and conventional oil.
Synthetic oil does not improve power ratings, however it does extend the life of the engine and considerably reduces the rate of sludge buildup.
No, absolutely not, that is the wrong weight oil for your Civic. Use 5w30 weight oil. You can use a full synthetic but use the correct weight if you want this engine to last.
yes you can synthetic oil can go in any engine
Lucas also makes a synthetic engine oil additive.. Yes.
I think it is a 2.5 horsepower engine. There are 4 oil formulas for Kawasaki lawnmower engines. I recommend you use the correct blend as stated in your owner's manual.
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.