With out a doubt you should use synthetic for a few simple reasons: 1. Fewer recommended oil changes (difference between 3K-6K miles vs every 35K for synthetic). 2. Begins lubricating sooner and don’t have a problem with heat breakdown conventional oils have, therefore do not produce sludge in your engine. 3. Though you never want to do this on purpose, if you ran all the synthetic out of your engine, as has happen to me, your engine will still run with out seizing up and destroying your engine. 4. You can now purchase generic synthetic brands, so not that much more than conventional now.