Yes, without any issues. That's what synthetic blend oils are (better than conventional oil, not quite as good as pure synthetic).
Yes, you can mix them.
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.
I think you can mix them without doing any damage to the engine. I think you can even add a quart of synthetic oil to regular oil if your engine is low on oil. Generally you would want the 5-30 in an area where it is colder.
If you do it yourself with conventional oil, about $60. If you take it in, closer to $100. If you want synthetic oil, add about $30-$40 more.
if your engine is knocking that means you need oil. go get an oil change or add a quart asap or the engine will burn out
yes it can... get royal purple it adds up to 15% of your stock horsepower
It would depend more on how many miles you go before it needs a quart of oil. A healthy engine should go between oil changes without adding oil.
0.25 galls are 1 quart
1.6 Liter engine is 4.4 quarts, 2.0 Liter engine is 5.5 quarts, 2.5 Liter engine is 5.8 quarts. Add more as needed when changing filter.
It should take 4 to 5 quarts of oil. Add 4 quarts and start the engine let it run for a minute then check the level and add if it needs the last quart.
For an accurate reading, after the car has been sitting level and cooled off, open the hood, locate and remove the engine oil dipstick (should be on the drivers side of engine). The dipstick will be marked where the full line and add line is. The engine oil level should be anywhere between the full and add mark. Add one quart of motor oil to the engine if level is at or below the add mark.
FWIW, my Honda dealer here in Mpls told me the Honda brand 0W20 oil is SEMI-synthetic and NOT full synthetic. That seems logical to me because they charge $39 for a 0W20 oil change and to get full synthetic almost anywhere it cost you around $60 for an oil change. Full synthetic Mobil 1 0W20 cost $6.50 a quart at Walmart, so you are already over $33 just for the oil. Add labor and a good filter and your at the $60 mark.