WARNING: Don’t do this to your Prius that burns oil

I don't think 10w-30 would have a catastrophic effect on a Prius engine. Your engine was well worn before you switched to this oil.

 

In the US, due to EPA regulations, most auto manufacturers specify energy saving motor oils. In many other countries, a choice of different oil viscosities are specified, depending on prevailing ambient temperatures.

For example, in Germany 10W-30 is allowed for temperatures down to 0°F (-18°C) for the Gen 2 Prius.

German Owners Manual Oil Spec 2007 by Fred_H posted Apr 26, 2021 at 10:33 AM

At temperatures above freezing, even viscosities as high as 20W-50 are allowed for the Gen 2 Prius.

 

Sounds like it's time to seek advice from someone else..........

Any chance you can go into this a bit deeper?
It makes sense too. It’s an aluminum engine block.

 

My company doesn't use anything else for their fleet vehicles last time I checked....

Oh and I think that I've identified the root cause for your trouble.
You've had this mechanic for how long?

Yeeeeaahh.
I think that the "change mechanic" light just came on.

 

This is a joke, right ?
If you really believe this story, you have been suckered.
"He" is either a moron or is getting a good laugh out of your gullibility.
Seriously.

 

running 10w30 would do nothing negative to your connecting rods, except increase oil pressure, film, and cushion between them and the crank.
it will definitely not damage your engine.
it will definitely not decrease consumption, if consumption had reached a point of 1 quart every 1,000 miles.

if the clearance on the con rods, and or crank bearings increased at the same time as running 10w30 , it was only a coincidence, and not causation.

if you stopped running the engine in time (quickly!) there's a chance you could replace your rings and bearings, and still get another 100-200k miles of service from it.

never run a knocking engine. always shut it down immediately and get it repaired before it makes windows into it's soul

 

More likely it blew a head gasket and then hydrolocked.

 

Using 10w30 oil in your engine by itself wouldn't have caused failure- something else happened. About the only "negative" things that would occur are taking a little longer to get oil to all moving parts on cold startup and a slight reduction in mpg due to more torque needed by the oil pump.

Posted via the PriusChat mobile app.

 

@M67v , I hope we have convinced you that your problem cannot have been caused just by using 10W-30 oil.

Once in a while, a spark plug can become loose or broken, even if it was properly torqued. That would be consistent with your symptoms, and is especially suspect because the plugs were recently worked on. Did you use a torque wrench? Was there much resistance when screwing in the spark plugs? Were the gasket seats clean?

Misfire, knocking sounds, and fumes could also be caused by a leaky intake or exhaust manifold or manifold gasket.

 

As several others have also tried to tell you............
I am telling you absolutely, positively that just changing to a slightly thicker oil, and it is just ever so slightly thicker, is NOT the cause of your engine failure. It just is NOT.
This is based on about 60 years now being a shade tree mechanic and auto enthusiast.
You need to STOP spreading around that false information.

 

If the objective is to increase oil film thickness, it seems that the emphasis should be placed on the "warm" grade part, not the "cold" grade part, because the oil film thickness is much thicker at "cold" than at "warm" anyway. For example, go from 5w-30 to 5w-40. What is the logic to do the opposite, such as going from 5w-30 to 10w-30? Could someone enlighten me on the logic?

In addition, does anybody have hard data to support the hypothesis of oil burning reduction by using a heavier oil? I want to know how effective it is.

 

This was your problem. The Mechanic was just an idiot.

 

Another issue with suspecting the oil is at fault in this scenario, which I don't believe anyone has mentioned, is that 10W-30 only increases the cold weight of the oil. This is an exceedingly small fraction of the oil's usage, only experienced on startup. Then when the oil is warmed up and it rises in weight it increases to 30 weight anyway, meaning that your engine can obviously handle 30 weight oil, so 10 weight is not an issue. I could maybe see switching to 20W-50 on an old engine, or 30W-60, if they even make such a thing, but increasing the cold weight of the oil will have little impact on the stress on your engine, but it will probably also have little impact on oil burning considering the small amount of time spent at that weight.

 

Running 40 weight in my G2 for years. Its got an aluminum head & iron block.

Not much difference between 5-30 & 10-30 except the 10 is a tiny bit thicker at cold temp who cares it's a 10 weight oil soon to be 30 weight oil. Soon as it heats up its a 30 weight oil.

Many people run 40 weight oil in there g2 its the best thing you can do to mitigate oil loss.

"Car was obliviously mistreated" pretty much explains it.

 

Well, there you go. It's no secret that it's not uncommon for professional mechanics to make mistakes or not take the time to clean everything up and make sure everything is in perfect condition. I am not saying that that the mechanic did something wrong. I am just saying that you can by no means rule it out.

You sold the Prius? Then the reason to continue this discussion would be to dispel the myth that only the single recommended oil viscosity is safe for the engine regardless of the operating conditions.

Using the same logic, you shouldn't think it was a coincidence that the engine got messed up not long after the spark plugs and coils were replaced. Unless you were driving the car in extremely cold temperatures or if the motor oil was of inferior quality, then it definitely was a coincidence that the oil was also recently replaced with an oil of slightly thicker cold temperature viscosity. (The warm temperature viscosity was the same.)