I use syntec blend. It does not gum up or do anything weird. Its the best of both worlds at a reasonable price. The Honda Tec says you can use 5w30 oil in your civic( esp in summer with no apparent difference or damage) but they recommend 5w20 when you can get it. Ken

 

ok i am gonig to switch from refined oil to man made oil but wha tshould i go with mobil 1 or castrol syntec

 

mobil one, but ive heard that once u switch to synthetic, then u cant go back to regular...im not sure if its true or not

 

yes that is true once you switch to synthetic you can't go back to refined oil

 

Sorry guys: you need to check out bobistheoilguy.com for real world, unbiased, factual information. Yes, there are sponsors for the site. What they say bears no more importance than the 10,000 members of the site, many of whom are fleet managers, professional mechanics, automotive engineers, petroleum engineers, and the like. There are huge databases with real world used oil analysis results to show what's good and what ain't. I've been a member for a couple of years, and I've seen nothing but good information regarding any and all aspects of lubrication and car care.
BTW: Oil is oil. Some comes from the ground, some from a lab, and some is blended! Some brands work better than others. You can switch back and forth from dino to synthetic to dino as much as you want. You don't need to flush the engine. Synthetic oil did cause a few engines to leak, when it was introduced, about 35 years ago. Very few to no problems now. Please, check it out. You'll learn so much, and get so hooked, that you'll drive all your friends crazy!