Change enginee Oil

To help you decide, here are a few pieces of information for your consideration:

1. In Japan, 0W-20 is an approved engine oil viscosity for 2G

2. Japan doesn't have much desert terrain. It might be appropriate to use 0W-20 if you live in the northern US where summer temps are not too high. If your high temp exceeds 100 degrees F it probably would not be a good idea to use 0W-20.

3. When I lived in southern CA, I tried 0W-20 on my 2004 one winter, when ambient temps are cold to moderate. At that time the car had logged ~70K - 80K miles. I found that the engine immediately started to consume oil, more than 1 quart over 5K miles. When I switched back to 5W-30 the engine continued to consume oil although at a slower rate, maybe 0.5 qt over 5K miles.

4. The good news is that mpg seemed to improve, perhaps as much as 5%. However I decided that for my purposes, 5W-30 provides better engine protection.

 

In a recent thread somewhere here about oil there were quite a few North American users running 0W20 (or 5W20).

It's interesting that here in Australia we generally use heavier oils than what I notice most in the US are using. Believe it or not but I've never even seen a 20 weight oil (anything-W-20) on the shelves of any supermarket or auto parts stores here!

Don’t know if it’s any different anywhere else but here most car manuals usually don’t specify a particular grade but give you a choice based on the temperatures you’re likely to experience. In the attachment below I’ve scanned the user manual recommendations for both of my current cars. Both the Mazda and the Prius are 2005 models. Notice that the Prius manual doesn’t even mention a 20 weight (anything-W-20) oil and the Mazda doesn’t recommend it if you’re going to operate in temperatures over 35C (95F).

I’m using 5W30 in the Prius and 10W40 in the Mazda.

BTW. 5W30 is about the lightest weight oil you’ll find in shops around here. I was at the auto-parts store yesterday and just out of interest I was looking at what were the max and min weights available. If the amount of stock on the shelves is anything to go by then by far the most common grades here are 40's and 50's (eg 10W40, 15W40, 20W50 etc). There's tons of choice in those grades and only one or two offerings at the lighter grades like 5W30. There were even a few choices to be had in the 60 weight range (10W60 and 20W60), but absolutely nothing in the -W-20 range.

 

It's helpful to understand what a multi grade oil does. A 5W-30 motor oil performs like a SAE 5 motor oil would perform at a cold temperature, but still has the SAE 30 viscosity at engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.

 

A TMS USA TSB, EG050-04, indicates that use of engine oil viscosity above 5W-30 may lead to no-start issues. Its interesting to see that in Australia, up to 20W-50 is deemed acceptable. (I'm wondering if the person who prepared that table just copied & pasted from the owner's manual for another vehicle like a Corolla...)

 

Thank you for providing the scan of the two owner manuals. It's important to have a reference from another country. Although the Mazda manual is a bit hard to follow, the Toyota manual is quite clear

The same motor that Mazda uses here that "demands" a 5W-20, will probably in Australia be filled at the service centre with a 10W-40.

I have always believed in matching viscosity to climate, all other things being equal. The modern "tight" motors do quite well on thinner oils, such as xW-30 or even xW-20. Unsure though how well they do in extremely hot climates, though the Fords and Hondas operated in the SW United States still appear to last a long time

At the other end of the scale, down to -40, you absolutely want the lightest oil you can find. A 0W-xx of some sort or another.

Perhaps at -20 C and colder it might, not in summer. The second summer I had my Prius, I had some heavy duty 15W-40 left over after servicing some of my equipment. I ran the entire summer on it, the Prius seemed just fine. No real difference in fuel economy - a couple of time I thought it perhaps got 1-2 mpg less, but that may have also been due to windy periods and highway driving

In the end, a 5W-30 will meet the needs of most drivers most of the time. A conventional 5W-30 should NOT be used colder than -30 C, it will be too thick to reliably pump at startup.

 

Ha I was thinking the same thing when I read it. It looks almost identical to the chart from the users manual of any and every other car I've ever bought since the early 1980's.

I know the chart says I can go up to 20W50 but I don't have any intention of going that high. The 5W30 I'm using in the Prius is however without a doubt the thinnest oil I've ever used in any car I've owned.

As for the TSB I assume that they are just covering themselves for the worst case possible scenario at the coldest possible conditions. Oil viscosity increase very rapidly as you cool it. I can post actual viscosity charts that show a 10W40 oil at 0C (32F) is significantly thinner (about 25% less viscosity) than a 5W30 oil is at -10C (14F).

Not a fair comparison I know, but my point is that given that I don’t see temperatures below 0C (32F) here, then even if I used 10W40 I’d still be better off (regarding the problem mentioned in the TSB or any other oil related issue for that matter) than someone using 5W30 at temperatures down to -10C (14F).

 

Yep I totally agree Jayman. I don't think I'd be comfortable using anything thinner than 5W30 here. (or 0W30 as there's no real difference at the high end)

As I suggested in the previous post I'm pretty sure I could comfortably use 10W40 in the Prius if I wanted to. The main reason I decided to stick with 5W30 was because it probably gives a little bit of fuel efficiency advantage.

As for the Mazda I'm running 10W40 but I'm sure it would also run ok on 5W30. The Mazda sees a lot less miles per year than the Prius so it's only getting one oil change a year these days. It might see only one or two days per year at less than 32F (and even then only a few degrees less) whereas it could see a dozen or more days over 100F. So I'm pretty comfortable with the decision to run 10W40.

One other thing about the 10W40 versus the 5W30 is that it's a fair bit cheaper to buy here. Because my choices are so much reduced when shopping for 5W30 I'm actually paying nearly $50.00 ($49) for a 5L jug (ouch yes I know oil and parts prices are crazy overpriced down here). And seriously that's about the cheapest name brand 5W30 I can find here.

With 10W40 there's heaps more choices, I can use something like Castrol GTX for about half of the above price, about $27 per 5L for the GTX or about $33 per 5L for the rather gimmickly named Castrol "Magnatec", which is what I've got in it (the mazda) at the moment.

 

So I wonder how much energy there is in a quart of oil since your engine was burning 2 fuels at that time... I'm asuming your mpg calculations are per gallon of gasoline.

 

interesting.