Use of 0w20 Motor Oil In Very Warm Climates

I am unclear why you think you know better than the engineers who designed the car. They think it needs 0w-20.

 

This is an excerpt from the Australian 2010 Prius Owners Manual. OW20, 5W20 and 5W30 are indicated as acceptable for the full gamut of ambient temperature. 10W30, 15W40 and 20W50 are also acceptable, except at lower ambient temperatures.



(There looks to be typo's in the temp range above: the leftmost 3 centigrade temp's should be negative.)

 

The engineers had nothing to do with the idea of using 0W20. It was the politicians who forced them to go that way. It's to achieve better fuel economy. I'm betting 5W30 would work just fine in the hotter regions of Arizona (probably not a good idea in Flagstaff though I'm betting also that it wouldn't harm anything but the ultimate fuel economy).

 

@ArizonaJon If you do switch to heavier oil, please post regarding fuel economy changes, if you notice any. There's also your mention of "conventional" oil, vs synthetic. I think either is fine, especially if you don't stretch the intervals.

 

I have switched from 0W-20 to 5W-30. Was dealing with some oil consumption ( about one quart every 4,500 miles). Switching to 5W-30 has lessened consumption to a quart every 6,500 miles. Did the swap at the 120 k mile change. Put 15 k on my 2010 Prius II since then. Have seen about 1-2 mph drop but I also changed tires and cleaned the intake manifold, egr cooler, egr pipe and egr valve since 120 k. Just did a 1,000 mile trip from around Sacramento to Palm Springs and back. Got 43 mpg average going 70 mph for the trip. This was improvement over last winter where same trip I got about 37 mph. The changes referenced were the variables. So IMO it is a negligible difference. In Northern California, the temperature will not get cold, so cold starts are not a concern I have. One data point for the thread that helped what I am dealing with.

 

Also did the PCV valve. It was still checking, but since I was there did the $7 valve

 

Your motor is liquid cooled, and this system is controlled by a thermostat.....which is set to??????? (anybody?)

Probably more than 118-degrees.
It's so vital to the operation of your car that the coolant temperature display is right next to the tachometer.

This means of course that the coolant temperature of your car during normal operation will be the same in Phoenix AZ in July as it will be in Buffalo, NY during January.

Don't over-think this.
Normally, I'm skeptical of OEM maintenance periodicity and fluid recommendations, but for the Prius I'm thinking that 0w20 is appropriate.
The biggest predictor of your motor's longevity will be how often you check your oil volume level.

Best of Luck!

 

My engine coolant always displays 195 degrees F after a 10 mile warmup. (I have no ups or downs to cause variation in load)

 

Yeah, and for someone on the fence, there's 5W20 too.

 

I've got it disconnected now, but highest I would see on my ScanGauge was 90C, maybe 91~92 occasionally. But as often as not, especially lower speed around town with more electric-only propulsion, temps would be around 75~80C.

 

well, you are clearly underthinking this as oil is air cooled in prius (and most other cars).

 

A valid concern about the extreme heat. I've been to Phoenix many times.

I'm a Prius "rookie" so my opinion is only worth about 5 cents... If I lived there, I would still use the factory recommended oil for my car. But for peace of mind I would change it a little more often. If the schedule says every 10K, I would do mine at 7,000 to 7,500. (And get the darkest window tint I could possibly get without being stopped by the cops. )

 

This list of xgauges hints you may be able to measure Engine Oil Temp F in a Prius, although it is experimental from 2011 and you would think they might have confirmed it by now.

 

That's a distinction that doesn't make a difference for an ICE in a normal passenger automobile.

The engine operating temp is somewhere between 180 and 190-degrees F, which pretty much means that the oil temperature isn't going to vary much between an ICE in Buffalo and an ICE in Aridzona.
The ICE is liquid cooled and oil lubricated.
Two different fluids.
Two different functions.

If oil temperature were important in this application, then there would be an oil temperature gauge right next to the tachometer or the engine coolant temperature gauge.
For some vehicles, oil temp IS important (think: TRD, Aviation, NASCAR, etc....) but for Priuses I'm thinking that there won't be any difference between the recommended viscosity and whatever flavors that home mechanics come up with.

Even in Arizona and Texas.

JMHO

 

incorrect assumption. we can argue whether that matters or not, but it doesn't change the fact that your statement is wrong. oil temp is not the same thing as coolant temp, unless there is oil heat exchanger (not in Prius or most cars).

 

you would have to be crazy to use 20 weight oil in Arizona. I'm running 0w40 mobil one in Florida. I can't imagine using even a 30 weight.

 

I am sorry for your car, maybe it's next owner can read the instructions.

 

They let anyone post here don't they

 

Well, the spammers are blocked quickly. For those giving help you do not want to accept, the best you can do is Ignore them. Click on my name and a black window will pop up, the rightmost option will Ignore me. Sadly, it will not ignore posts that quote me, so you may still see a tiny bit of my content. (It does ignore entire threads I start)