0W20 oil, need honest truth.

Maybe 2-4% on the mpg.

Any synthetic oil including low-viscosity will 'hold up' better than conventional oil including Toyota's products.

My used oil analyses on 0W20 synthetics (2001 Prius) always looked good. Others have posted similar results at Prius Chat.

To any who 'experiment' with non-standard choices such as this, it is in your best interest to get used oil analyses. Your car, your driving conditions. And if you do, please post the results at Prius Chat too.

We talk a lot about warranty implications of such decisions, but so far I know of no Prius having engine problems, and the company trying to void warranty coverage thereon. It could happen someday though. In which case, it would be very handy to have a record of squeaky-clean used oil analyses. Don't you agree?

 

I'd suggest not going outside the manufacturers recommendations. The ICE is built to close tolarerances, and they state what ought to be used for a reason. Their engineers aren't dummies. Two different options only, in the manual.

 

Any automotive engineer is going to tell you that if the engine went through it's validation tests with 5-30 then that is what you should use. It isn't just guarantee you want to consider but ultimate lifetime longevity. That is one of the things you pay for isn't it.

 

I just did some math for you. Assumptions:

-Gas costs $3.20
-5000 mile oil change interval
-50 MPG nominal fuel economy
-Either 2% or 4% MPG gain from using 0W20

For a 2% MPG boost, you save approximately $7; it's $14 for 4%. I know there are reasons other than $$ for wanting better fuel economy, but decide for yourself whether that savings is worthwhile

 

I'm with Seamus, use what the manufacturer recommends.

 

For another angle, Ford now recommends 5w-20 for a lot of their 5w-30 engines, and I've heard the Motorcraft 5w-20 has a larger amount of moly in it. Which may be to make up for the lower viscosity.

If you want to stay within spec, I just saw 0w-30 mobil 1 at wal-mart in the 5qt jug. You will likely only see a noted improvement with it during the winter though.

 

Was the price difference between conventional oil and the synthetic oil factored in? $6 and change verse $2 and change would negate any savings with a 5000 mile oil change.

 

I thought about that, but decided to leave it off. It wasn't clear what the OP's other oil choice would be. Would he use synthetic oil at the recommended viscosity, rather than 0W20? Or would he use regular dino oil? It's also not clear whether the 2-4% improvement stated above is from dino to synthetic 0W20 or from synthetic 5W30 to synthetic 0W20.
You're right though, that the more expensive oil probably offsets the cost savings.

 

For what is worth I saw no difference at all in mpg's going from Mobil 1 10-30 for 6000 miles to 5-30. No mpg increase whatsoever. I doubt you'll see any mileage difference in any weight oil you use as long as its Mobil One. I doubt you'll see any in 0-20 either. Probably some in moving from dino to synthetic though. Your on the wrong track. Mpg savings are in learning how to drive and plan your day with the car. Just pump up the tires and drive slower.

 

the fact that you live in Vegas, I would be shocked and surprised if you had better results from a 0 Weight oil versus a 5 Weight. If anything for your climate you may want to consider a thicker weight for those hot summer months. I would just stick with the 5 W 30 (only mess with the 0 weights if you live in one of the truly cold climates such as Minnesota or Maine, Canada, etc...)

 

I've seen a lot of 'thin as water' comments for 0w. The fact is that the 0w at its cold temp range is thicker than a -40 heated up to operating temps. The 0w flows quicker at start up than a 5w, which gives better protection and less resistance. It may give slightly more benefit to an auto stopping car like a hybrid.

The numbers on the oil bottle, and what engine manufacturers recommend, is just a labeling system. The actual viscosities of different brand 30 weights can range from close to 20 to nearly a 40.

 

Once the car hit operating temps, there wouldn't be a difference between 5w-30 and 10w-30. So unless you are mostly making short trips where the engine never has a chance to heat the oil up, there won't be a difference in your mileage.
I agree that it is mostly your driving technique. That said, I believe I may have had an improvement with a 0w during the winter. I'll give another try in the Ranger once it gets cold again.

Now, I've seen this explanation on the ddifference between synthetic and dino oils once and thus it may be wrong. A dino oil base is of the viscosity of the first number, and it contains modifiers to bring it up(actually down) to the second number. The synthetic is the opposite; base is the second number modified down. Which partly why the syn gives better protection, and probably why there isn't a 0w dino.
Whether that is true or not, a 5w-30 has more additives, and thus less lube, than a 5w-20.

 

For a 30 weight oil there are three choices. 0W30, 5W30 or 10W30. At operating temperatures, many 0W30 oils are thicker then 10W30 oil. The first number relates to cold temperature viscosities and the second number relates to operating temperature viscosities. 0W30 oils are not as thin as water. For that matter, 0W20 oils are not as thin as water either. Also, there is a pretty wide range of viscosities that are still called 30 weight oil.

I use 5W20 Motorcaft brand oil. It is a partially synthetic oil that comes in reasonably priced 5 quart jugs at Walmart. I use it because I feel that the thinner oil reduces start-up wear, operating oil temps are reduced, gives a little better fuel economy, is a really well designed oil. Yes, it violates the mfg recommendation, but I do oil analysis every time I change my oil. It is also, just a little bit thinner than a thin 5W30 oil. So it is not really too much different than a 5W30.

 

I've posted very detailed information on this subject

http://priuschat.com/forums/care-ma...ting/39648-extended-oil-change-intervals.html

http://priuschat.com/forums/prius-technical-discussion/42457-6m-8k-oil-change.html

http://priuschat.com/forums/care-maintenance-troubleshooting/42609-oil-change-why-difference.html

We recently had a *very* heated debate over oil quality and viscosity, and oil change intervals. A couple of forum members were nice enough to post the oil page from their owner manual, one from Japan and another from Spain

In the EU, Toyota Prius has a 12 month or 16,000 km oil change interval. THis is twice as long as our interval, with no ill effect. Of course, the standard ACEA spec A1/B1 oil is far superior to our crap API oil.

If you find a dual-rated oil, it is almost always a synthetic. Eg, API/ILSAC SM and GL-4 is a weak spec, but dual rated to ACEA A3/B3/B4 is a *very* tough spec to meet. Cars in the EU that spec A3,B3/B4 oils typically have a 18 month/30,000 km oil change interval. A lot of GM/Opel cars and VW have 24 month intervals, up to 50,000 km

I use 0W-20 year round in my Prius. I'll use the 0W-20 in winter in my FJ, the 0W-40 in summer, based on UOA

I've attached the pdf of the Japan and Spain owner manual pages. I'd appreciate it if members in England, Sweden, and Australia would also scan and post the appropriate pages

You will notice that in the EU Toyota suggests a 5W-30, but allows up to a 20W-50. In Japan, 0W-20 to 10W-30

 

-Either 2% or 4% MPG gain from using 0W20?
Who tested this mpg gain? I don't think there would be any gain at all. As soon as the ehgine heats up, the oil isn't 0, it changes to 30. So how could there be any gain? You may never see 0 unless during very cold days.

 

At operating temperature, a 20 weight oil will be thinner than a 30 weight oil. Also, part of the API rating requires a specific fuel efficency improvement of a 20 weight oil over a 30 weight oil.