Toyota Service Said Don't Switch to Synthetic Oil

In the UK with petrol over $10 a gallon (over £6 UK) 1to2% saving on fuel over the life of synthetic oil pays for the oil.

 

To see the improved MPG 1-2%, you need to use reduced viscosity oil. For a Gen-II Prius this means 0W-30 Mobil-1 AFE Advanced Fuel Economy or equivalent other brand. The 0W-30 Mobil-1 AFE is considered to meet manufacturers requirements for the normal 5W-30 specified oil in the owners manual. Now then *some* Gen-II Prius owners take it a step further (go against owners manual - living on the wild side) and use even lower viscosity 0W-20 to try for even better MPG. In winter this may be OK but I have not tried this myself. I feel like I am seeing better MPG with 0W-30 AFE this winter, but in summer I expect less benefit over 5W-30.

About the lowest price for Mobil-1 is $5/qt on the very best sales.
Walmart 5-QT bottles gets close to that price in my area. Believe it was $6.50/qt at Toyota parts store today, but of course that is not the best place to get it. Frequently I buy it myself and give it to the guy changing the oil (more frequently change it myself).

 

Using 20 weight in a Prius is very common and not against the owners manual.

Toyota recommends 20 weight in the Prius.

 

Gen-II in USA is 30 weight, right?
Newer versions are 20.
I am thinking we are in Gen-II thread.

 

Yep 5W30 for the Gen2 is the original spec. In Canada and Japan however they've also "back spec'ed" it for either xW20 or 5W30.

Question for BritPrius. Are you running xW20 or xW30 over there in the UK? I guess at $10+ per gallon you'd want to try anything you could to reduce fuel consumption. We never even see xW20 down here in Australia, most cars here run xW40 or thicker!

 

Don't switch to synthetic?

Depends on what propaganda you want to embrace.

I've done the usual internet investigations and it seems to me that the truth is that in the early days of synthetics, there was a problem with higher mileage vehicles that made the switch developing leaks.

Mobile One and The Synthetic Oil companies will tell you they have improved the product and addressed the problem.

My own experience? I switched my 16 year+ 120,000 mile Honda Accord to synthetic oil and never had a problem.

So going on my own personal experience and what I've read mostly from makers of synthetic oil? I don't think it's a problem.

 

I have been running 0w20 since first oil change with no problems and no measurable oil use between 10kmile oil changes. Now at 80k oil comes out still looking very clean and fit for further use, I save it and use it in my chain saw lawn mower and strimmer.
0w20 is listed as suitable for the gen2 by Toyota and from 2008 on handbook and is marked the preferred choice.
I have a couple of friends that have converted to 0w20 from 10w30 in 2005/2006 Prius, and booth have reported MPG improvements of around 2%.

 

Toyota UK also offered a 60,000 mile warranty on the engine of the gen2 using 5w30 synthetic oil with a 10,000 mile oil change interval.

They now offer a 100,000 mile warranty on the gen3 Prius with a 10,000 oil change on 0w20 oil. If they were concerned about engine damage they wouldn't offer such a warranty on either car.

Am I correct to assume the US Prius engine warranty was only 30,000 miles on the gen2?

 

...yes we are talking almost 40-years ago synthetics came out and had a few little bugs apparently fixed by improved formulatons.

 

So what you're saying is the Toyota Service Technician that recommended NOT switching to synthetics was only 40 years behind the times?

 

I believe you are correct for 2006. And we had 5000 mile drain interval with 5W-30 with no difference for conventional vs. synthetic lube oil.

 

I have switched to synthetic oil in high mileage cars and not had any problems. My Prius was bought used and it got its first syntheic oil change at about 15k miles.

 

No matter what car I buy or at what mileage I always switch it to Mobil 1 synthetic.
Hi performance and extended drain intervals cannot be beaten.

 

Probably true for newer engines. However, after my nephew to over my well-maintained '87 4-Runner with 97k miles, he switched to synthetic and suddenly I'm hearing how happy he is with the 4-Runner, except for the oil leaks.

 

I Agree. Switching to synthetic oil makes sense only if

1) There are no oil leaks, and
2) Engine is not burning any significant amount of oil

otherwise, you will be leaking or burning the expensive stuff

Thanks,
- Alex

 

Here's one to through in the mix. The Prius C uses the same complete engine and drive system as the gen2 Prius. The Toyota oil of choice for the C is 0W20.

 

It is true that it is a 1NZ-XFE, same as the Gen2, but it has been modified considerably since then. Weigh change, compression ratio change, etc.

 

The only engine modification that I am aware of is the electric water pump and perhaps heat recovery system. Perhaps someone can fill in more detail of changes that may affect lubrication.

 

+1 The reports of older mid life engines developing oil leaks as a result of switching to synthetic are not uncommon.

I would be wary of switching to synthetic on any higher mileage engine.


iPhone ?

 

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