Switched to 5w-20 from 0w-30

Hi Josh,

I'm familiar with the two attached TSBs. The boxed note on the first page of EG018-06 excludes Classic/2G Prius from the list of covered vehicles.

EG050-04 applies to Classic/2G Prius and the version attached is current as of April 2007. That TSB continues to recommend 5W-30.

If you have access to more current info please post that document for our benefit.

Last year I was made aware that the Japan domestic market 2G Prius owner docs allow use of 0W-20. I tried using Toyota 0W-20 synthetic last winter in my 2004 while in southern CA and realized ~5% mpg improvement. However the engine started burning oil - using around 1 quart after 5K miles.

I switched back to 5W-30 synthetic but the engine is still consuming oil, at the rate of ~0.75 quart at 7,500 mile change intervals.

The odometer now reads 95K miles. The car did not consume a noticeable amount of oil prior to my using 0W-20.

I don't know whether the oil consumption was provoked by use of the lower viscosity oil or just naturally resulted from engine wear associated with the relatively high odometer reading.

 

I ran my '04 most of the time I owned it (Sold it this summer) on Mobil 1 0W-20. No difference in valvetrain noise, no difference in summer fuel economy, good used oil analysis reports

My '07 FJ is a different story. Running the dealership 5W-20, Mobil 1 5W-20, or Mobil 1 0W-20, the valvetrain went tick-tick-tick. I'm not talking about the vacuum switching valve, that's a different noise

Running the made in Germany Castrol Syntec 0W-30, or Mobil 1 0W-40, the valvetrain is silent. No difference in fuel economy with 0W-20, compared to 0W-40, in my FJ. With 0W-20 and 5W-20, used oil lab reports indicated very high nitration, which is absent when I run the Castrol 0W-30 or M1 0W-40

I intend to run Mobil 1 Turbo Diesel Truck 5W-40 as a "summer" oil. It comes in a 5 litre jug, which is perfect for my FJ refill capacity. In other countries, the same 4 litre V6 will generally spec a 5W-40, 0W-40, 15W-40, in temps >+50 F

It would be one hell of a coincidence that the car didn't use oil until you put in the 0W-20, and now it uses oil

This is why if I have a high mileage vehicle, I never EVER switch brands of oil, or viscosity. Especially to go lighter, there could be just enough extra wear that you will always use oil from that point

Have you tried a "thick" xW-30, like the made in Germany Castrol Syntec 0W-30? If the oil consumption goes away, you probably have your answer

Note: with my Prius, in summer driving I never noticed any fuel economy difference between 5W-30, 0W-30, or 0W-20. Even running 15W-40, maybe 2 mpg less

 

It's not just the Prius. With my FJ Cruiser, if they put in the "recommended" oil capacity, the oil level is about 4mm over the full dot.

Of course, with the FJ, Toyota used to recommend a straight 90 gear oil in the rear axle, if over a certain temp, and an 80W-90 as a "winter" grade. Which means in almost all of Canada, changing the gear oil twice a year

Those early owners who switched to synthetic 75W-90 received a lot of flak from dealerships. Including snotty comments like "customer used synthetic gear oil, warranty void."

Then Toyota came out with the TSB recommending a synthetic 75W-85 gear oil. Didn't know they made a gear oil that light. Usual cost is around $80 a quart

So a lot of us FJ owners just use a good synthetic 75W-90 and hope our rear ends don't self destruct. At least I don't have fender bulges

 

At least you're honest enough to have looked into this. Most likely, based on some of the horror stories on this forum, the average dealership wouldn't even give a s***

 

I've used AMSOIL 0W30, MOBIL AFE 0W20, and currently using MOBIL AFE 0W30 ...

All three, all good, returning to the AMSOIL 0W30 in 7500 Miles, and sticking with it for the life of the car :thumb:

 

What is the lightest, most fuel efficient motor oil you can use in your Prius?

 

Since you have a 2010 you should use 0W-20. Toyota sells that synthetic oil under its label at the local Toyota dealer, or you can buy that viscosity elsewhere.

If you have 2G or Classic then 5W-30 is the correct viscosity; however some owners have used lighter weight oils. This makes sense in cold climates.

 

I have used Amsoil SSO 0w-30 for the last 2 years, 16000 mi change interval but have switched back to Mobil 1 0w-30. I was noticing some clatter when the ICE started up cold -not bad but annoying. After going back to M1 and stock Toyota filter, the engine is as smooth as when it was new (I have 119k on it). I'm going to go with 10k OCI and expect to have no problems.

 

I have been using Mobil 1 0w-30 in my 05. The 0w-30 helped reduce valvetrain chatter during cold starts in winter time compared to 5w-30(yes, I use a good oil filter with anti-drain back valve). As you aware, Toyota released a TSB back in 07 stating that the 1NZ engine family as well as many other Toyota engines could use 5w-20 engine oil with no negative side effects. At that time we switched our bulk oil to 5w-20 (I'm a Toyota service tech) and put it in all the applicable 5w-20 engines. The other day a Prius driver was complaining of a noise when driving through curvy sections (ended up being a pile of gravel/mud/debris interferring with front sway bar operation). While on the test drive I was extremely impressed with how quiet the valvetrain was with 5w-20 oil in it (car had 34k miles on it). So, my oil was due to be changed on Friday so this time I picked up some Mobil 1 5w-20 (still using the Mobil 1 M1-103 oil filter) and switched to that. All I can say is WOW, the difference is night and day. There is no more valvetrain chatter climbing the hill leaving my house (after stage 1 warm-up) in the morning. I just wanted to post this tell my experience and to gather others opinion/experiences.

Thanks for reading!

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I have used 5W 20 on my 05 for a long time. I have 134,000 miles on it, and it burns no oil at change intervals of app 7,500 miles. I have used either Amsoil XL or Valvoline Synpower. I also use WIX filters. I live in Texas, and it has no problem with the incredible heat down here.

 

Congradulations on catching that Pat, I was just getting ready to change oil.