Synthetic or regular oil?

I'm about to possibly buy a 2007 -- with a 2.7 litre engine. 136,000 km on it.

Owner says he runs synthetic in it. Should I stay with that or switch to regular oil? Is one or the other better? is it a big deal to have a bit of residual synthetic in it when/if I add regular petroleum oil?

 

You can switch back, although some may say that switching back may cause issues with seals and you'll end up with leaks, but I think that only applies to those who already have slight leaks and issues with seals, if at all especially with the advancements they've made in synthetic oils since their introduction.

The true question is, why would you want to switch back? There are many advantages to synthetic oils, but the biggest con about it is some think its expensive when it's actually not. You can go for longer on synthetic oil before needing an oil change than you can on conventional mineral oil so the cost difference is pretty much a wash.

Here's a decent article about it. I'm sure some of the more seasoned members will chime in as well.
http://www.topspeedracer.com/synthetic-vs-regular-oil.html

 

It really comes down to how often you want to change it/ what makes you feel good. I feel better changing it every 3k with dino oil but many people prefer to go 7-10k with synth. price is the same either way. My only other thought is that if you change the filter more often you are better off. Plus I just like working on my truck!

As far as mixing and switching it shouldn't matter on a tight motor. Only old high milage engines that have leaks should stick with dino oil and use a high viscosity. I used to run diesel truck oil in my 91 BMW with 250K on it and she never leaked!

also read the similar threads at the bottom of the page

 

I like to run conventional oil because change intervals are 5000 miles and that helps me remember to rotate my tires. Dumb reason, I know, but it helps me stay on top of things.