Check engine light!

[efusco]

Well, indirectly they answered the question.

You deserve to have the recommended 5W-30 oil used. The dealer should correct the mistake for free. And it does have the potential to affect your gas mileage...but not your warranty I wouldn't think.

[jayman]

Well, it sounds like local dealers are allowed to deviate from the generic recommendations based on specific climate and/or driving conditions. If this did affect the warranty coverage, then I doubt Toyota USA would allow them to do so. It would otherwise become a legal mess.

For a climate like Van Nuys CA, I doubt there will be any issues with engine life compared to a 5W-30. Given the climate, a regular 10W-30 may be more stable than a regular 5W-30.

If you look at BP Lubricants retail oil recommendations for that motor, they offer much more specific recommendations (Synthetic and regular oils) based on climate. For example: any temperature consistently over -12 C you can use a 15W-40, and any temperature consistently over -7 C you can use a 20W-50.

You also see similar motor oil viscosity recommendations from European manufacturers like BMW and Audi. Since the same motor is used in North American, EU, Australia, etc, it stands to reason you may want to tailor the viscosity to specific driving conditions.

A lot of the motor oil recommendations for the North American market are driven by API marketing and by odd EPA fleet-wide fuel economy requirements, most of which are theoretical and not noticeable by the average driver. But a theoretical 5% "improvement" on a vehicle that gets 12 MPG isn't really noticeable by the driver, whereas a car that gets 50 MPG *will* have a noticeable difference in fuel economy.

This is sort of like how Ford and Honda recommend a 5W-20 oil for the North American market. I haven't heard of any motors blowing up due to using 5W-20. The same motors in Europe typically specify at the lightest some sort of 5W-30 or 10W-30, usually some sort of xW-40.

In Australia, you'll probably see as a minimum an xW-40 and probably a 20W-50. Perhaps our Australian forum members can tell us what Toyota Australia fills their Prius with?

I would think that if you operate under extremely high ambient temps, especially at high speeds and WOT, you'd want something thicker than an xW-30. But to confuse the issue, synthetic oils are far more stable under such operating conditions than regular oils with heavy polymer additives.

Consider Mobil 1 0W-30: it's a "borderline" SAE 30 at operating temp, but it's very stable too. So although you may be right on the edge, long term testing with UOA has confirmed it holds up very well even at 10,000 mi oil change intervals.

In Van Nuys CA you may gain 5% in fuel economy just by substituting Mobil 1 0W-30 for the 10W-30 now in the crankcase. Although it exceeds all the requirements, the local dealer may have a s*** if you tell him to run 0W-30.

With Honda cars, like the Civic and especially the Insight, either a 5W-20 (Semi synthetic) or 0W-20 (Fully synthetic) are specified for North America. The same motor - at least in the Civic - in Australia needs a 10W-40 and can run a 20W-50. There may be up to a 10% fuel economy hit if you compare a 20W-50 to a synthetic 0W-20.

If you get 45 MPG running a 20W-50, you may get 50 MPG running a 0W-20.

I'm sure that in the case of Honda - maybe even Ford - their long-term reliability testing didn't uncover anything bad when running an xW-20 under "typical" North American operating conditions.

I used to have a 1992 Honda Prelude that I purchased new. When I had it in SLC, I ran Mobil 1 15W-50. That car only got 30 MPG so there was no difference between Mobil 1 5W-30 and Mobil 1 15W-50. What I did notice was that the motor was *much* quieter and a bit smoother. That's subjective, but when the outside temps were 105 F or higher and I was driving at 80 MPH on I-15, I felt better.

In Canada, I ran either a synthetic 5W-30 all year round, or a synthetic 0W-30 in winter once that viscosity came out. At -40, the last thing you need is a blown front seal or a broken oil pump, and yes those catastrophes still happen around here. Especially over this winter, as it was long and brutally cold with many -40 nights.

To sum up, I don't think going too thin will have any immediate consequence. Especially with a good synthetic, there won't be any long-term consequence either. However, going too thick especially in cold temps can have immediate and catastrophic consequences.

If a dealer in Van Nuys feels that a 10W-30 is best for that climate, about the only consequence I can predict is a slight loss in fuel economy. It may not be much, maybe 1-2 MPG.

However, if you want to keep the dealer happy, *and* gain some MPG, why not run Mobil 1 10W-30? This is a very stable Mobil 1 product (They all are) and is also a "thin" SAE 30 at operating temp. You keep the dealer happy and also have the potential to gain maybe 1-3 MPG.

The Mobil 1 site appears to be down at the moment. I was going to attach a link to their Mobil 1 10W-30 product page.

Hope this helps.

[IsrAmeriPrius]

Just because someone wrote 10W-30 does not mean that is what was put in the car.

Did it occur to you to ask the service writer or the service manager or director if that indeed is what the technician used? Only a few of Keys Toyota service writers handle the Prius. I found service adviser Elias Pilichos, who handled my first service and a minor warranty problem, to be particularly knowledgeable about the Prius.

[prberg]

Thanks for the great info guys. jayman... that helps to see how the different weight oils work. I have been considering mobil 1, but since I'm going to stay at the 5,000 mile interval (for warranty purposes) and don't really run my car under extreme conditions (It does get hot here in summer but I don't think the engine is under extreme stress) I don't know if synthetic is worth it for me.

I guess I'm not that worried about the 10W-30. I know it's not really going to ruin my engine. I guess it's just that when the dealer does any work on the car I expect them to know exactly what the car needs and if they use different oil it would be nice if they tell me they did (and why they did it). And maybe the paperwork is just wrong. Since I didn't notice it till I got home, and since it wasn't a huge deal I just let it go. (Other than writing to Toyota to make sure it wasn't a problem with them)

As always... you learn a little something new every day.

-Peter B

[richard schumacher]

<div class='quotetop'>QUOTE(prberg\";p=\"77775)</div>

After looking at my paperwork closer.. I see when they did the service that I didn't ask them to do... they used 10W30.  Shouldn't they know what oil the car needs more than me??  Doesn't it say right on the cap... 5W30??  They probably overfilled it too.. I better go out and check right now.  Is it really that hard? I mean really.  
[/b]

Maybe they think you need it for all that high-speed driving in the desert :_>

[prberg]

haha. I guess me and V8Cobrakid are just trying to prove that the Prius can do anything that a non-hybrid can do. (yeah... that's the reason). Although we get warning lights in the process. Guess the Prius is trying to give us a friendly reminider to be careful.

Of course both oils are 30W when warm so should protect the same at high temps.

[rick57]

<div class='quotetop'>QUOTE(prberg\";p=\"79828)</div>

haha.  I guess me and V8Cobrakid are just trying to prove that the Prius can do anything that a non-hybrid can do.  (yeah... that's the reason).  Although we get warning lights in the process.  Guess the Prius is trying to give us a friendly reminider to be careful.

Of course both oils are 30W when warm so should protect the same at high temps.[/b]

Or are you guys trying to find the upper limit of the Prius?

[Kyle Pehrson]

Hi Rick whats up!

[rick57]

<div class='quotetop'>QUOTE(Kyle Pehrson\";p=\"79869)</div>

Hi Rick whats up![/b]

Hey Kyle, not much. Just trying to keep up on all these questions. Don't be a stranger and visit often, :wink:

[Kyle Pehrson]

Hey I got the answers to the new A/C Test. Have you taken it yet?