Mobil 5w40 turbo diesel syn.

[patrick_g]

Gee Pat, maybe you are a canidate for synthetics!

What if you were to use and synthetic, low weight (like 0w-20 or 0w-30) oil in your Prius? Since the engine is so much smaller than typical cars of its size, I'm wondering if the combined improvement in viscosity losses and frictional losses would have a more dramatic effect on performance and mileage. Also with the constant start/stop of the engine, would that help improve its durability and lower wear?

Just a theory. Maybe Toyota uses a low weight synthetic already.

The Prius certainly stops and restarts the engine more than most any vehicle on the planet, I think, but the way it does it prevents problems, It is designed to do this. IT has control of the valve timing, spark, and fuel injection. The starter is not an anemic 12 volt starter but a powerful electric motor that can propel the car and uses hundreds of volts from the BIG battery not the little 12 volt battery for the accessories.

Here is the sequence of events when it starts or restarts:

1. open the valves with no fuel being injected
2. crank the engine up to a high idle speed with the spark turned off.
3. when the oil pressure comes up and everything so everything is lubricated then the valves go to normal operation, the fuel and spark are turned on,the motor quits cranking because the engine is running.

Pretty harmless operation that is repeated thousands and thousands of times on a trip of reasonable length. The starter has no bendix and so does not engage and disengage, it just changes roles from motor to generator as controlled by computer. The transmission having no clutches or torque converter has no wear associated with starting and stopping the engine. The transmission is actually a sun and planetary gear set which effectively simulates a CVT in its actions. There is no reverse gear in the tranny. Backing up is by running one of the electric motor/generators backwards.

Starting and stopping the engine incurs no additional wear to the engine or any aux components. The only thing getting exercised any differently from a long continuous engine run in their setup is the computer executing some lines of code. Not injecting fuel or not sparking the plugs, or not closing the valves should not incur extra wear. Shifting to reverse just reverses the flow of electrons to the motor to back you up as there are (I say again) no clutches or other moving parts except some plain old gears in the sun and planetary gear system.

Pat

All this is transparent to the driver, it just works (perfectly for us so far for 50,000 miles plus.) I don't know whether or not the Prius is a good candidate for synthetic. It gets new oil and filter religiously every 5K miles.

I just checked a couple Prius sites and as you may well imagine there is no consensus regarding synthetic versus dino oil. Oil change intervals were mentioned from 3500 to 15,000 with this, that or some other filter, Fram getting poor reviews from some but Amsoil and Toyota filters getting all good reviews. MFG recommended change is 5K miles and dino oil is standard. Some change the filter 2-3 times for every time they change oil and go out to 15,000 miles per oil change. Some test their oil and the test results support their longer change intervals.

Ask 5 guys and you get 10-15 opinions on most automotive issues especially oil.

 

[crashz]

Wow! - thats impressive. Thanks for the explaination, as I've always thought they were more akin to the typical powertrain in convential cars, just with the added electric motor.

Does the engine alway spin when not running and electric motor driving the car? You mentioned no clutches so I envision this spinning with the valves open and simply pumping air.

This would be a fun car to tinker with.

 

[patrick_g]

Wow! - thats impressive. Thanks for the explaination, as I've always thought they were more akin to the typical powertrain in convential cars, just with the added electric motor.

Does the engine alway spin when not running and electric motor driving the car? You mentioned no clutches so I envision this spinning with the valves open and simply pumping air.

This would be a fun car to tinker with.

No the engine does not spin when it is shut off and you are coasting or under electric power only. Less parasitic losses and wear.

I am not the most savvy guy regarding the Prius tranny. It is pretty simple mechanically as it has no clutches, no torque converter, no reverse gear, and doesn't "shift" gears per se. At moderate speeds if you let up on the accelerator just a bit it tends to go to a higher speed drive ratio (lower gear ratio, we call it high gear in conventional tranny) and if you "punch it" (risking whip lash from the sudden acceleration... ) the tranny smoothly slides down its essentially infinite choice of gear ratios to a "lower gear" for acceleration. Of course the accelerator is just an input device to the computer which the driver uses to tell the computer how much power you want. The computer takes other stuff into consideration, in addition to "throttle demand" and decides what ratio to give you. This ratio varies over a continuum depending on demand, response, etc. If you take your foot off the accelerator then the ICE (usually) is quickly turned off and restarted again when needed. Whether the car is propelled by electric motor, ICE, or both depends on several factors which are monitored by the computer.

The driver does not need to be aware of ANY of the above. You put gas in the tank like a regular car and drive it. The computer does the rest. This is similar to modern warplanes where the pilot's control inputs are actually "requests" to the computer that then does what it can to give the pilot what he asked for.

The only computer controlled aspect of the car that is not really smooth is computer assisted traction control and that is a bit "herky jerky" but that seems to be the nature of the beast. Punch it with poor traction and it accelerates by fits and starts, maintaining good safe control but not silky smooth.

I don't have a perfect understanding of how it all works, mechanically as when an undergrad I studied physics not automotive engineering, but I appreciate the results in action. It is pretty darned good. As far as the software is concerned, I have never seen better control software and I make that judgement with years of software experience and a masters in software engineering.

There are several Prius sites and at some of them there are folks discussing various hacks at the software and some hardware mods too. Some added more batteries for greater electric only range and so forth.
Pat