0w-40 oil in a 140K miler?

[kocho]

Do you have any thoughts on using a 0w40 oil in my '02 prius, which is rapidly approaching the 140K mile mark?

I've been feeding it 5w30 so far (all Mobil 1 synthetic, of course) and had let it go on the last oil change for 10K miles or so and intend to continue doing at least 10K b/w changes going forward. I've only had the car for less than 30K myself and I'm sure the previous owner used the cheapest oil and did not do changes often - the car was in a rather poor condition in terms of maintenance when I got it, including signs of dried/baked oil visible around the engine pour spout area.

The question is about the 40 relative to the age of the car. Supposed to be thicker than the 30 at operating temperature and for an older engine I thought this might be actually good. Any thoughts? I did the change actually a few days back and I seem to feel the engine work a little noisier than usual. But I am not sure if I am imagining things or not - it has not been the most quiet engine so it may just be that I'm paying more a ttention to it now...

And please, no "the manual recommends ..." type of answers

[FireEngineer]

Before you do the change over get a used oil analysis. If your Mobil 1 is showing good wear, good TBN and has not sheared the viscosity too bad the 5W30 is fine. The 40 weight would give less MPG and would not help unless you were losing oil between changes from engine wear.

Wayne

[jayman]

Agreed. If you suspect the motor has been poorly maintained, a used oil analysis is essential

The Mobil 1 0W-40 European Car Formula is an excellent oil, and I use it in my FJ Cruiser. It's considered a "light" 40, so there should be minimal impact on fuel economy compared to Mobil 1 5W-30

[jayman]

Originally Posted by kocho

And please, no "the manual recommends ..." type of answers

Actually, the manual for the EU market Prius suggests up to a 20W-50, depending on ambient conditions. In the EU, a 0W-40 is a very popular choice for extended oil changes and engine protection, with minimal impact on fuel economy

Indeed, many Opel, BMW, and Mercedes models require a 0W-40 for their extended service intervals of up to 24 months or 30,000 miles

[Patrick Wong]

Originally Posted by kocho

Do you have any thoughts on using a 0w40 oil in my '02 prius, which is rapidly approaching the 140K mile mark?

...The question is about the 40 relative to the age of the car. Supposed to be thicker than the 30 at operating temperature and for an older engine I thought this might be actually good.

Since you are approaching winter, its not clear that 40 weight oil will help unless your engine has problems with oil consumption. However this is a good experiment for you to try.

Should you find that you experience engine no-start problems in the winter (i.e., DTC P3191), I suggest switching back to xW-30 oil.

[kocho]

Thanks for the replies. I've read that EU spec suggests up to 50, so I figured it would probably be safe to use 40.

I have pretty much no oil consumption, so that's not an issue.

I'm too lazy to go for oil analysis, yet I've been keeping my Camry and the Prius on 10K/1yr change intervals on synthetic oil... Have not heard anyone have a problem with this so I suspect it is OK with good oil and not too hard use...

[Gokhan]

Originally Posted by kocho

Do you have any thoughts on using a 0w40 oil in my '02 prius, which is rapidly approaching the 140K mile mark?

I've been feeding it 5w30 so far (all Mobil 1 synthetic, of course) and had let it go on the last oil change for 10K miles or so and intend to continue doing at least 10K b/w changes going forward. I've only had the car for less than 30K myself and I'm sure the previous owner used the cheapest oil and did not do changes often - the car was in a rather poor condition in terms of maintenance when I got it, including signs of dried/baked oil visible around the engine pour spout area.

The question is about the 40 relative to the age of the car. Supposed to be thicker than the 30 at operating temperature and for an older engine I thought this might be actually good. Any thoughts? I did the change actually a few days back and I seem to feel the engine work a little noisier than usual. But I am not sure if I am imagining things or not - it has not been the most quiet engine so it may just be that I'm paying more a ttention to it now...

And please, no "the manual recommends ..." type of answers

No, no, no!

Always stick with the thinnest grade of oil recommended in your car's manual. You will get the maximum gas mileage and longest engine life.

Once you make the switch to a thicker oil grade, there is no going back to a thinner grade. Thicker oil means higher oil pressure. Higher oil pressure means your cylinder rings, valve seals, and various other seals in your engine will endure higher pressure, and this will permanently deform them. Not only that but tolerances of metal parts in your engine will also change and adjust to higher oil pressure. All this change is bad, and it will result in increased oil consumption, more engine noise, and, the worst part, less smooth engine performance. At the end the overall result is to decrease the life of your engine.

It's a myth that thicker oil grade will decrease oil comsumption in high mileage cars. The truth is it won't. Although thicker oil passes through tiny gaps more slowly for a given oil pressure, increased oil pressure caused by thicker oil compensates for this and you get similar or more oil consumption when you switch to thicker oil.

Perhaps the only exception could be during summer months in hot deserts where your engine runs much hotter than otherwise. Then, if you switch to a thicker grade, say from 0W-30 to 0W-40, during extreme heat, such 100+ F temperatures, you might see a benefit. This is because increased temperature will thin your oil, and 0W-40 in a very hot engine will behave like a 0W-30 in a normal-temperature engine. But do this only if a thicker grade is recommended for such high temperatures in your owner's manual. If not, your cooling system is powerful enough that your engine temperatures don't change much under extreme heat and you should use the same grade during very hot weather.

So, the bottom line is that always stick with the thinnest oil recommended in your owner's manual throughout the life of your car, no matter how many hundred thousand miles you have on it. The only exception would be if a thicker grade is allowed for extremely high temperatures in your owner's manual. In that case you can switch to the next thicker grade during 100+ F or so weather, or more accurately, whenever your engine-temperature gauge shows higher than usual engine temperatures, but still avoid very thick grades such as 20W-50.

One other note: If your manual recommends 10W-30, you can always use 5W-30 or 0W-30 in all temperatures. Likewise if your manual recommends 5W-30, you can always use 0W-30, and if it recommends 5W-20, you can always use 0W-20, regardless of the temperature. Using 5W- instead of 10W- or 0W- instead of 5W- oil will increase your gas mileage and extend your engine life. Decades ago 5W-30 oil was not recommended for very high temperatures but modern motor oil doesn't have this problem and 5W-30 is always better than 10W-30, at all temperatures. Likewise 0W-30 is always better than 5W-30 and 0W-20 is always better than 5W-20, regardless of what is recommended in your owner's manual and at all temperatures. The only caveat: 0W- oil comes only in synthetic form and you end up spending more money (about $15 more for an oil change) and straining your wallet. Also, obviously, do not use xW-20 if your manual recommends xW-30 or vice versa. But, as explained, it's more than OK to go as low as 0W-xx for 5W-xx or 10W-xx. The digits before the W indicate the cold-engine and "W"inter performance and 0W-xx is always the best for automative engines.

[jayman]

In other parts of the world, folks frequently switch among viscosity. Eg: 20W-50 summer, 10W-30 or lighter for winter. I have a 1984 Ford worktruck at my hobby farm, its entire life the motor had 15W-40 summer and 0W-30 winter. It now has 528,000 km on it, motor still pumps up 130 lbs of compression

An oil like Mobil 1 0W-40 meets far stricter specs (ACEA A3/B3 for example) than the other Mobil 1 oils. This oil is specifically designed to meet severe service and extended oil drains - up to 24 months or 30,000 miles - over in Europe

The oil also has far higher TBN and detergent action compared to other oils. It may help dissolve the worst of the sludge and varnish buildup, especially in the crown land and ring land area of the pistons.

I run the 0W-40 in my FJ in summer, and 0W-20 in winter. Excellent used oil analysis results

[uvm1969]

I have been using Pennzoil Platinum synthetic 0W-20 in the heat of Texas, and my 2005 has 86,500 miles and is going strong. I would think the 0w-20 would be perfect for both the colder winters in Maryland, and the hot, very humid summers.

[kocho]

Originally Posted by jayman

An oil like Mobil 1 0W-40 meets far stricter specs (ACEA A3/B3 for example) than the other Mobil 1 oils. This oil is specifically designed to meet severe service and extended oil drains - up to 24 months or 30,000 miles - over in Europe

The oil also has far higher TBN and detergent action compared to other oils. It may help dissolve the worst of the sludge and varnish buildup, especially in the crown land and ring land area of the pistons.

These are the reasons, especially the extended change interval, why I was tempted by the 0w40 vs. the 0w30 or 5w30. Plus I read than in Europe up to 50 is OK so I figured it should be fine here in the US as well Lastly, there was a very good deal for under $30 bucks for 5 quarts with a mobil filter included (that alone is $10 usually), so I could not pass it up...

I ran my Mazda MPV on 0w30 and it was recommended to use 5w20 on it - have not heard of one issue when folks have done that (and many have as the 30 is more readily available than 20).

Now, for an instant 5mpg boost I just need to remove my roof rack more often