Used car purchase, what oil to use conventional or synthetic?

lookup you service history via the toyota owners website. you can pull up detailed service info from each dealer visit. most likely the conventional bulk oil 5w30 was used. it varies what bulk oil is used based on the dealership. generally 5w30 is the standard for Gen II but toyota also back-specified 5w20 and 0w20 for this generation as well.

 

I am not sure it makes big a difference whether you use dino oil or synthetic, but these days you can get 5-qts of Mobil-1 synthetic for $22 bucks and change at Walmart. So I've gone to synthetic in my cars. Keep in mind Gen2 barely takes over 3-qts to fill so that 5-qt container will have some left for next refill. If you go to Mobil-1 web site I think they say you can you can safely put in synthetic any time even if dino oil was in there. For the winter I go with Mobil-1 0W-30 advanced fuel economy, but Ca. you are warmer so I do not know what I would use there. The other nice thing you can get various flavors of syntheic (fuel economy, extended drain, high mileage).

 

To directly answer the question, and I'm not trying to be flippant: it matters if it matters to you.

In other words, if you're inclined to obsess over brands or types, feel there might be an advantage in one particular oil, or synth vs conventional, indulge yourself. It's not a big expense.

With the miles that are on it, while Toyota's now authorized 0W20 for the older Prius, it might be better to stay with the originally spec'd weight.

Personally, I just put in the Toyota brand oil. With our spec being 0W20, it's synth anyway. It's pretty cheap too, always under $6 per liter.

 

Whichever you use, make sure you check the oil often to get a feel for how much oil it uses, if any. The best oil in the world won't do anything if it all gets used before the next change.

 

Conv goes 5k between changes, syn goes 10k. That's what I do