So I find it very interesting that Toyota put this engine in the C. It is the same engine as used in the Gen II's. I don't know if the transmission is the same though, certainly the software would be different I suppose. Also Toyota recommends 0W20 in this engine. So is this kind of telling me I can run 0W20 in my Gen II? This weight oil is somewhat of a controversy in Gen II's I think. Toyota shakes their head at using anything other than 0W20 in the C, like the 0W30 I now run in my Gen II.
From what I have read it is similar to the Prius Gen I (or maybe II engine), but has some changes...Here is a quote I read about it...not sure it tells the exact details pertaining to your question about oil...but interesting none the less..maybe some more informed folks can shed some more light on the nitty gritty deails of the differences... -M "Under the hood sits a revised 1.5L Atkinson cycle four-cylinder engine, essentially the same 73HP mill used in the first generation Prius with some key modifications. To improve efficiency, Toyota removed all belt driven accessories. Even the water-pump is electric on the diminutive four banger. Because the Prius liftback is wider than a Yaris, Toyota created a new Hybrid Synergy Drive CVT transmission that is smaller and lighter. In addition to the new transmission, the c also uses a new 144V battery pack and inverter that are smaller and lighter than the regular Prius. Total system output is 99HP (about 35 less than the 1.8L in the Prius)"
Toyota said they redesigned engine 70%. If they changed tolerances, size of the mains, etc, engine would need different oil.
I would say its highly doubtfull they changed all that. Its mainly the same engine that they used in 1997. It is beltless now though, so less parasyhtic load. The main change from the gen II is a different hole for the engine block heater, and lower max rpm, lower peak torque, peak hp. The new units in the prius c and gen III use cooled egr, which can mean a cooler running engine. That makes enough changes that I would not assume they use the same oil. Here people are discussing it on the gen II. http://priuschat.com/forums/gen-ii-...service-said-dont-switch-synthetic-oil-4.html Most of the hybrid parts have changed from gen II - mg1, mg2, psd, added cooled egr with ehr. They removed the thermos for heat with the new system, and new gas tank eliminates the bladder. Now its an electric water pump. They are also using a smaller battery with similar but fewer cells.
Running cooler means that if clearances are kept the same, viscosity can be lowered to allow less shear without breaking lub film.
Here is the pres release. Looks like a lot of changes. Here is one "a micro-polishing process that reduces friction of the reciprocating assembly" among other things.
actually, it's not doubtful they redesigned the engine at all.. they made drastic changes to the 2AZ-FE engine in the 2007.. as well as placing a TSB that same year noting the newer designed engine was to use 5w20 vs. the 5w30 the older 2AZ's used to run on. (changes did include piston design and as a result a different compression ratio.. along with improved oil flow.. cooling.. etc..) so... yeah.. even if it's the same base engine design on the first place.. they do have revisions that may warrant a different weight oil.. in the end... it's best to use what your owner's manual suggests.
You can use 5W20 or even 5W30 without harming anything except for the oil change interval (if using conventional oil) and perhaps fuel economy. I would say it is the other way around, that design and manufacturing has changed to allow for use of 0W20 without causing consumption problems, rather than having a design that dictates only 0W20 be used. Toyota has been pushing all motors to run 0W20 in the past 5 years for fleet fuel economy. Many people run 0W20 in Gen II as well as Gen 1 without issue. To me, the material differences between the C motor and Gen II are the electric water pump, cooled EGR, and lack of the coolant heat storage tank nightmare. They may have tweaked 70% of the parts, but it is still the same basic motor.
I thought that might be one of the major differences. It also drops NOx and may reduce deposits, I don't know. Thanks for the doc. I hadn't seen it before. I don't quite get it, I assumed they micro-polished the crankshaft before. Are they they doing more parts, or maybe just a better process that reduces friction. When they went to the 2NR they micro-grooved bearings to hold the oil a better way. I said minor, not no redesign, and it still appears minor. They switched the valve timing a little going from gen 1 to gen 2, which was also fairly minor. agree and said this in the post. You can though listen to people on the forum to see if there is better oil to use +1
This engine uses VVT (variable valve timing), if I recall from the back of the brochure. VVT is designed to use a specific viscosity oil. While the differences in viscosity between the various companies for the same weight oil, and between various 5w and 0w -20s, is minor and likely not to be an issue, moving to a 30w oil might cause issues. Or not. Depends on the design. Try 'em all and tell us how it goes.
So to wrap up this thread I decided to ask my local service manager what their position was on running 0W20 in my Gen II. His reply was pretty much what I expected, so here it is. I don't think he was shouting at me (CAPS ON) but on the other hand perhaps he has been asked this question numerous times.
