Prius Oil Type

Why change now?
The 5w30 got you this far.....in fact I'd consider switching to a high mileage blend of the same viscosity.

 

Why bother going synthetic now? Keep running same oil same viscosity. if you go thinner you will start losing oil. Your already seeing oil loss I bet.

 

If it ain't broke, don't fix it.

 

Thinner oil will likely accelerate your loss. As far as brands, Toyota's oil is fine by me. Up here bottled liters of their 0W20 are currently $5.91 at nearby dealership. There's also amenable to selling me bulk, for $3.85 per liter.

 

1. If your changes are at 10,000 miles, then immediately reduce the OCI (oil change interval) to 5,000 and switch blends (not viscosity) to a high mileage blend.

2. Check your oil every time you load fuel to get an idea if the quart loss is steady state or increasing. Remember...your car is basically through its normal life cycle.
Don't get offended.
I' not impugning your car, but a $2500 to $5,000 repair would just about exceed the street value of your car and if you have a really bad year...(brakes + HVAC + traction battery) and you're not mechanically inclined then you're probably hoping to get another 50,000 miles down the road with your car still using oil at about 1q/5000 miles and not needing a heart or liver transplant.
Start thinking about an exit strategy.

3 Do nothing else while your burn rate is static!!! Many people try to make things up to their car for what they perceive to be past sins by buying special crap (and most of it is crap!) for their car in the snake-oil section of their local parts house, and they often exacerbate the problem.

You're in Illinois, and so you're probably starting to sweat the VET thing....or you're going to be shortly when you start throwing codes, unless Priuses are allowed to pollute as much as they want to.
The reason I bring this up is that modern cars are designed to burn unleaded gas cleanly.....not oil.

Be careful if you ignore the brilliant advice in #3 above and get somebody to "clean all of the gunk out of your engine."
Used catalytic converters are cheap, but the install fees can be rather high......and there are oppressive states that do not allow one to replace their cat with a used unit, and insist on putting a "new" $1500 catalytic converter into a $5000 car. (see #2 above.)

Good Luck!
Keep us posted!!

 

If you must change to a full synthetic, Mobil 1 0W-30 would be a better choice since the 2G Prius is spec'd to use 5W-30. Especially if you are concerned about engine oil consumption, there is no point moving to a thinner viscosity oil (which 0W-20 would be, compared to 5W-30.)

If you are changing the oil at 5K mile intervals, your engine is doing very well considering it has logged 202K miles. This is very normal, don't worry about it and just make sure the oil level stays above the bottom dimple on the dipstick in between oil changes.

Well, your engine has done very well with 5W-30 conventional up to this point. There is no great reason to make a change.

 

For years, the original owner of my 2005 changed oil every 3 months, at the dealer.
In 2012, he switched to 5w-20, again every 3 months at the dealer. I bought it in mid-2015.

Not burning any oil as of March, 2016. I change every 6 months. 5w-30 blend.
. . . Now if I can just get the oil change crew to stop putting in four quarts instead of .... you know.

 

What is the spec'd quantity?

That's one thing our local dealership (who's doorstep I never darken) does right. Soon after purchase we went to an open-house for new owners, toured the service department: they had graduated pitchers at the ready, drawn from a large bulk oil supply (Ed the Fox will be along shortly to extol the perils of bulk oil, no matter), so no "just dump in the rest of the bottle".

 

Be cognisant: any oil with the description "high mileage" is designed to swell rubber, such as valve guides. It should be used as a last resort with an oil burning engine, and once you start using it you pretty much have to stick with it: reverting to non high mileage oil will cause the rubber to shrink more than it was to begin with, with greatly increased oil consumption.

 

I'm using Prius 2008 with 180k mileage. Should I use the 10W-40 instead of 5W-30 for such a hot weather in Cambodia?

 

THIS.

If it isn't using any oil between changes.........don't change anything.
And certainly don't switch to a thinner oil.

 

Maybe.
ONLY if it is using more oil than what has been "normal" in the past.
But it certainly won't hurt.