Prius 2010 oil change advise (urgent)

+1

If it concerns you greatly then you could buy some 0w20 and get whoever changes your oil to use that instead, but do not expect to notice enough of a change to justify the added expense.

Good Luck!!

 

I think a 10w-30 would be plenty thin enough. He has zero cold starts. 65 degrees F being the coldest temp. He could probably get away with a synthetic straight 30. 10w-30 is just more viscosity stable compared to 5w-30 and would tolerate heat better over 10,000 miles.

One issue you're trying to prevent is the oil sheering down below a 20w and then turning into sludge from the high temperatures. It'll also provide less protection if it gets too thin.

Preventing the oil sump from getting below the fill mark on the dipstick will also prevent sludge and varnish
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Have a look at the graph at: https://goo.gl/images/YVk1Xe

A motor oil with a temperature of 0C is 4-5 times as thick as the same motor oil at 20C.

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Motor oil temperature doesn't track coolant temperature without an coolant-to-oil heat exchanger. Priuses don't usually have these equipped. The only way to know your oil temp is to use an aftermarket temperature gauge.


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NO it will not be a problem.
Stop OBSESSING about this and use what the dealer recommends for your area.
Several of us here have recommended that too.
You are worrying about this WAY too much.

 

That's a distinction without a difference.

We're not talking about the Dakar Rally.
We're talking about a 1.8 liter inline four with funny breathing habits and tuned for a whopping 100BHP more or less and is designed for ops in the <4,000 RPM range and for the purposes of pulling a 3000 pound egg shaped car with up to 5 pax at speeds that are generally less than 100MPG.

Oil temps are moderated by the engine coolant, and adding an additional oil cooler would be extra redundant.

 

I agree with this. For peace of mind, do a search on bobistheoilguy.com for UOAs (oil analysis of used oil). For example, someone from Nebraska ran 0w40 in his 2005 Prius with good results.

The first number is the winter rating. Your winter rating makes no difference to your car since your climate is tropical. It can actually be a detriment since VIIs tend to break down leading to lower weight oils.