Regular oil vs. synthetic

I know there was another similar thread, but it didn't address my question. I just bought a 2000 Tacoma, SR5, TRD, 2.7, 5sp man, 4wd, 120K miles. I want to change all the fluids, including engine oil, tranny & xfer case oil, F & R diff oil. The guy on the phone told me that with that many miles I should just stick with regular oil. He also seemed to indicate that if the vehicle has not had synthetic in it in the past, I shouldn't start now.

What is the problem with mixing oil with synthetic? How do I tell whether the truck has had synthetic in it, and why shouldn't I go ahead and change to synthetic now if it hasn't had it before?

 

the thing with synthetics is their cleaning abilities, which can tend to cause small holes in the seals..........just on occasion though. i think you will be fine running synthetic if you wanted to......just watch to see if your motor starts to have any leaks. it may even be a good idea to run a high mileage synthetic with that many miles on your truck, just my opinion of course.

 

Synthetics are more "slippery" if you have small holes in your seals that regular dinosaur oil might not slip through you might get a leak if you put the more slippery synthetic in it.

 

Thanks, guys. I thought maybe there was some sort of compatibility problem, sort of a water-and-oil type thing. I bought the Mobil 1 High Mileage 10w-40 after reading a thread on bobistheoilman.com, which was recommended on the other oil thread. Pretty good stuff on that page. I know Toyota recommends 5w-30, but I figured I was ok going with 10w-40, with 120K on the engine, even here in Pittsburgh.

 

i think you made an excellet choice. shouldnt give ya any problems at all!