I've got ~26K miles on a 2007 Honda Civic. Oil Can Henry's is upselling me on Castrol Syntec vs conventional oil. Should I bite?

Not necessary. You’d extend the engine life by using synthetic, but the Honda is pretty bullet proof even with regular. Might consider synthetic later in the engines life.

The old rule of thumb was to only use synthetics from the very first oil change and then stick with them. But your car has been manufactured to much tighter tolerances than those older engines and 26K is not very many miles so it would be okay to switch. However you should still stick with synthetics for each subsequent oil change.

No.

It’s not good to switch between natural and synthetic. They use different detergent types that do not play well together, which has been known to be detrimental to engine seals. Once you pick a type (synth or no) stick with it. As @prescottman2008 just said.

Stick with the manufacturer’s recommendation and even though the 2007 is the first year to not require a timing belt change, do it anyway. That is still an interference engine design. If the belt breaks you have the potential to destroy your engine.
Of course all owners of MY 2006 and earlier, know this. Right?

@worriedguy: Wait, timing belt? I was just asking about synthetic versus conventional oil… How is that related?

It’s more important to change your oil frequently than to switch to synthetic. If you are letting more than 3K miles go by, change your habit. It’s the single most important thing you can do to extend the life or your engine.

thanks @dpworkin. From the other information I’ve gathered, changing to synthetic can actually extend the mileage or period of time between changes — from 3K miles with conventional motor oil to ~6K with synthetic.

Of course I’m sure it varies by car, age of the vehicle, and which motor oil you use, but it’s not clear to me that changing my oil after 3K miles still makes sense if I switch to synthetic…

What I meant to say was stick to a good grade of conventional oil but do not extend the mean time between service to more than 3K miles.