original engine oil on prius C?

Actually Mobil 1 is probably still made of mostly Group IV (PAO) and V base oil, as most people on the Bob is the oil guy forum believe. The record-low cold-cranking viscosity of Mobil 1 0W-20 is almost a proof that it's a mostly Group IV (PAO) oil. Amsoil is almost certain to be entirely Group IV (PAO) and V.

Toyota Genuine Motor Oil 0W-20 made by ExxonMobil and sold in US, as well as the Japanese variants, are believed to be mostly Group III+, with perhaps some Group IV mix.

Yes, Group IV is superior to Group III+, at least in theory, offering less friction, more oil life, and cleaner engine. That's one advantage of Mobil 1 and Amsoil over Toyota Genuine Motor Oil. But then, in real world, the overall performance of the oil is what matters, which is greatly affected by the right balance of the base oil and the additive package. With a better additive package, an oil made with a Group III base oil can easily outperform an oil made with a Group IV (PAO) base oil.

So, which one you should use? Again, if you are an MPG-purist or hypermiler, you should definitely use the Toyota Genuine Motor Oil 0W-20, which is specifically made for more fuel economy, thanks to its very high viscosity index. As far as whether M1 or TGMO results in less wear, that's impossible to say at least without seeing the results of thorough engine tests. For a cleaner engine, M1 is probably better, but a cleaner engine hardly means anything or makes a difference, as long as sludge doesn't form or deposits aren't excessive.

 

You can probably negotiate down the TGMO 0W-20 SN/GF-5 (Made in USA by ExxonMobil) to about $5 per quart, which will be cheaper than M1 0W-20. Then, you can return the M1 0W-20 to Wal-Mart.

TGMO 0W-20 is a better oil than M1 0W-20 in my opinion. It has a much higher higher viscosity index than M1 (216 vs. 173), which means that the oil will be thinner throughout the temperature range, and this is guaranteed to give you more MPG and save you money and let you boast about your MPG to guys who use M1. (See this link about the importance of viscosity index for getting more MPG.)

TGMO, thanks to Toyota's strict specs for reducing engine wear, has more antiwear additives (ZDDP and moly) than M1 as well, which may possibly result in less engine wear. Note that the SM variety of M1 notoriously had high-wear issues but the SN variety seems OK.

There is really no need to resort to a generic oil like M1 while there is a great custom-made oil for Toyota engines, blended according to Toyota's strict instructions with the ultimate fuel economy and lowest wear in mind.

 

M1 is 26$ per 5qt jar in Walmart, it may be cheaper then TGMO?

With respect to VI it is not always higher is better. The PAO base VI is ~140, lower for Base III. To get higher to 173 you have to add polymer modifiers. More so to get to 216.

Well the problem with polymer additives that they don't last, so the 216 oil will be out of spec quicker, and byproducts will gum up engine.

IMHO unless you live in cold climate with regular sub-zero starts there is no advantage in running higher viscosity oils.

Let the religious/oil wars begin :cheer2:

 

Ah, OK, that statement is actually incorrect.

You are right that it used to be that Group IV (PAO) base oils had more viscosity index than Group III base oils. But, nowadays, the new Group III+ base oils have a higher viscosity index than Group IV (PAO) base oils. That's one reason Toyota, Honda, and major Japanese oil blenders use Group III+ nowadays -- higher viscosity index than PAO. PAO viscosity index is limited to around 130 - 140, but the Group III+ viscosity index can be made higher by making more linear molecules. See the Sustina Web page about their W base, where W base stands for Group III+ base oil that originates from wax, which results in very high-viscosity-index linear molecules. For more technical info on Group III vs. Group IV, see the articles section of the Yubase Web site, Yubase being the world's largest Group III base oil manufacturer. (This is not to say that Group III+ is superior to Group IV in all ways -- Group IV is usually more stable (longer life), has less base-oil friction, and more cleaning.)

Therefore, it's not true that you need more viscosity-index improvers -- special polymer oil additives -- with Group III or high viscosity index simply implies more viscosity-index improvers. TGMO does use a very high viscosity index Group III+ base oil to start with. If you really want to see if the viscosity-index improvers might be a problem, compare the 100 C used-oil viscosity to 100 C fresh-oil viscosity (using used-oil analysis [UOA]). More the drop in viscosity in used oil means more low-quality viscosity index improvers were used in the oil, which then permanently sheared.

 

You can only get it from the Toyota dealers. Unfortunately, having it shipped from an online Toyota dealer would cost a fortune, and you need to actually go to a dealer.

The other problem is that the price the dealers ask varies greatly. The cost to them is about $4 per quart and you should negotiate with them and try to get it for around $5 per quart. Then, you have a good deal. There is no guarantee that they will go down that low. My nearest dealer asked for $12 per quart! Fortunately there is a dealer 25-miles away where I can order online for about $5 per quart and then go there to pick it up.

Therefore, first check with your nearby dealers. Otherwise, you will have to use the M1. Your other option is to get the oil change at the dealer instead of doing it yourself. This might be cheaper sometimes. Just make sure that they put the correct oil -- TGMO 0W-20 SN. I am a big-time DIYer myself.

 

I purchased a case, 12 quarts, Toyota banded 0W20, from our local Toyota dealer for $5.50 per quart. Mobil One oil is currently
on sale I believe at NAPA, for $5.79 per qt.

 

The Toyota part no for a quart bottle of TGMO 0W-20 SN/GF-5 made and distributed by ExxonMobil in US is: 00279-0WQTE-01

Good Toyota dealers sell it for about $5.30 - $5.40 per quart. Other Toyota dealers might charge more, even much more.

 

When I bought my new Acura RSX 10 yrs ago I had grave misgivings about the long change intervals, the 5w-20 viscosity recommendation, and I had questions about which type and brand of oil was best. So I did oil analysis every oil change for nearly 100,000 miles. I discovered several interesting things:

• My engine took about 30,000 miles to fully break in and the wear metals stabilize.
• The long change intervals were actually conservative.
• 20 weight really was the best recommendation for engine wear. 30 weight gave no better results and negatively affected gas mileage.
• Expensive Mobil1 gave me higher wear metals than much cheaper Chevron Supreme and Valvoline Durablend (this was the best performing oil I tried as far as wear goes.)
• My car consumed Mobil1 0w-30 at a much higher rate than any 20 weight oil.
• Synergen's very expensive ester and diester group Vsynthetic 0w-20 was the worst performing oil I tried as far as wear metals goes.

The experience taught me that beautiful spec sheets and high priced synthetic oils don't necessarily give the best results. As a long time Mobil1 fan boy this was difficult to accept.

 

How about flash point? oxygenation? resistance to thermal breaking under extreme conditions? Group III base don't last as much as homogeneous PAO, they have lower flash point. They break down faster and gum up engine. And sludge is more serious issue then wear, most of the time.

I am yet to hear of engine failure due to excessive wear, but I have seen many engines rebuilt due to sludge clogging oil filter.

BTW it is a moot point either oil is probably good enough to outlast car. AMSoil is superior to Mobil-1, but why you'd care if on M1 car will go 380,000 miles?

 

Yes, Group IV is superior to Group III in terms of chemical stability and cleaning, at least in theory.

I was pointing out that Group III+ has a higher viscosity index than Group IV, which results in better fuel economy because the oil runs thinner in regular operation and when cold, yet as thick as an oil with a lower viscosity index when it gets really hot during severe conditions.

Therefore, most Prius owners would appreciate the higher fuel economy resulting from a high-viscosity-index oil like Toyota Genuine Motor Oil SN/GF-5 0W-20.

Overcleaning is actually bad for your engine. Because when an engine oil cleans too much, it also removes the protective antiwear, antiscore, and antifriction films (such as formed by ZDDP and moly additives) on metal surfaces, which leads to increased wear. Mobil 1 had notorious high-wear issues in the past because of this problem.

Sludge is only a problem in few engines, and it usually results from bad engine design, using the wrong oil, using poor-quality oil, exceeding the recommended oil-change interval, or not performing the oil and filter change properly. I wouldn't worry about sludge in most engines.

I think for most people fuel economy and wear are the most important things. You're right that a lot of people don't keep their new cars for more than ten years, and most engines nowadays easily last for 200,000 miles, but those buying used cars will appreciate an engine with less wear. People appreciate the $$$ savings resulting from a more fuel-efficient oil as well.

 

I drive my Prius C on the interstate mostly at 60 to 70, so my tripes are always 0 or 1 percent EV modes after 60 miles interstate commutes, meaning my engine is running most of the mileage I drive, am I still good with the 10K intervals?

 

Yes, most modern engines can easily go 10,000 - 15,000 miles on quality synthetic oil.

 

We have 69,000 miles on our Prius and change oil every 10,000 miles.

When I change the oil I only fill with 4 quarts so as
not to over fill.

After 10,000 miles when I change the oil and filter nearly
4 quarts comes out, in fact it just about fills
a gallon container.

Oil used currently is Mobil One 0W20 synthetic, but next
change I will use Toyota 0w20 synthetic to see if there
is any difference, espically in mpg's..

 

The capacity is 4.4 qt. If you fill only 4 qt, it will give you 10% less protection and safety margin against the acids formed during the combustion process. Likewise, your recommended oil-change interval will decrease by 10%, as the bases in your oil that neutralize the acids will be depleted 10% sooner. In addition, the particulate count in your oil will be 10% higher -- another reason for a shorter oil-change interval with less oil put into the engine.

 

This is an interesting thread as I am picking up my new C4 in few weeks and was beginning to think about oil, oci's and oil brands. I have long been a Mobil 1 fan, but I am thinking I will try Toyota 0W-20 in my C and go with the 10k oci's. Still, old habits die hard and I want to be sure about this, you guys positive 10k is okay on the factory fill?

 

Bump. First post. This seems to be the official priuschat motor oil nerd thread, so here I go. I believe y'all may find this to be new and interesting.

I purchased a new 2015 PriusC Three on July 16, 2015. The day before, July 15, 2015, Ravenol came to market in North America with a ground breaking 0W16 motor oil. I studied the information carefully. Having had vast, positive, previous experience with using Eneos Sustina 0W20 VI 229 motor oil, I was not at all reticent to use this Ravenol product.

At 4623 vehicle miles, I replaced the factory fill, TGMO 0W20 VI 216 motor oil with the Ravenol. I now enjoy an approximately 5% improvement in fuel economy. I will be conducting successive used oil analysis to substantiate my conjecture that Ravenol is a superior product in every way.

If anyone is interested in dialoguing me about the details of this oil, I will be glad to do so. I am no scientist, but do have a knowledge base as a very well informed consumer.

 

i have been using raven oil for years. it's head and shoulders above am soil. i used to get 60 mpg, but with raven oil i'm consistently above 70. nice to know i'm not the only genius in this house!