Looked at a lot of Prius and the dipstick oil looks kind of tarnished

huh, mine have all clear as a bell. in fact, sometime i think there no oil at all! maybe buy a new one?

 

third one, they all been same. but low mile. how many mile on yours?

 

Probably just from crankcase vapors which deposit and accumulate over time.

 

Toyota 0W-20 looks darker than others.

I've no qualms about it, all I've used.

 

My only experience is with a gen 3 using Toyota full synthetic 0W-20 oil.
I am totally amazed that the engine oil looks nearly new (justly slightly darker than new, a dark yellow) at 10,000 miles when ready for the recommended change.
I have used domestic cars and pickups for the last 40 years using Mobil 1 synthetic, also changed at 10,000 miles.
The Prius on Toyota 0W-20 is the first one where the oil looked near new at 10,000 miles.(and always still full) I suspect this is in part do the amazing good ring seal of the little Toyota engine and the fact that it does not run much at idle.
A normal trip for me is at least 40 miles one way, so the engine and oil gets fully warmed up with each trip.
I started using Toyota synthetic in my Dodge Dakota pickup(4.7) last oil change.
Dodge recommends a 5W-30 synthetic, but in our cool climate and light loads, the Dodge 4.7 seems to like the Toyota 0W-20, so when I had the annual 10,000 mile service done to my Prius last week, I bought another 6 qt of Toyota oil for the next change in the Dodge. Price over the parts counter is comparable to what I have to pay for Mobil 1 locally, so why not. Hopefully the Mobil1 and now toyota synthetic oil will prevent the oil sludging problem the Jeep / Dodge 4.7 is known for.

 

I wouldn't recommend running 0w-20 in a 4.7L V8 engine when a 30w oil is specified by the manufacturer.

 

What exactly do you mean by "tarnish oil" ?
Maybe it is the color of the dipstick that is confusing you ??

Motor oil doesn't have just one color; different brands even look different coming out of the can.
And they get even more different as they are used a bit.

 

Or even better, bring a paper towel or napkin with you - then you can see the color of the oil stain on the white paper surface...

In any event, the color of the used engine oil is not particularly important and different brands will get dark at a different rate. What is important is how often the engine oil has been replaced, and whether you see contaminants like antifreeze in the oil.

 

Yep, It's tarnished allright! 83k miles

 

Same thing on our '05 when we bought it with 47K on the clock. Complete dealer service history oil changes etc. I chalked it up to VAT oil. I shined my dipstick up with 0000 steel wool and a spritz of brake parts cleaner. It's minty fresh now. But Patrick's wisdom is spot on again.

 

Are you referring to the area a few inches above the measuring end?

 

No, I was just making fun of the "always" in OP's comments.

 

I would not worry about the "tarnish" above the actual measuring part of the dipstick. My '04 has 154K miles and does not show any of this. Yes, I have seen it use oil between changes. But, the next change it may not use any. I have used synthetic oil since the 15k oil change. My thoughts are that the rings needed to seat before using the synthetic oil. I use what ever synthetic is on sale at the time. It seems that Mobil 1 is on sale more often than the others. Castrol and Royal Purple work just as well, and I have had really zero problems with the engine. My usage seems to be related to high speed runs (over 80 mph) for hours at a time. I let up and drive sanely the oil usage drops.