Any appreciable gain with 0w-20 oil?

Well you really made two viscosity-reduction changes, so you *might* see 2-3% MPG increase-
(1) you vetoed the 30 weight called for in the owners manual to 20 weight (Toyota apparently OK's that)
(2) you went with 0W Advanced Fuel economy which improves low temp viscosity.

I plan to refill Mobil-1 AFE 0W-30 which is approved for 5w-30 vehicles. I am less brave than you, but also I gotta use up the 0W-30 on my garage shelf.

I saw this brochure at VW service (our other car) yesterday (paraphrasing here): " to Improve MPG up to 20% - change air filter +10%, tune-up +5%, inflate tires +3%, lube oil change to AFE +2%"

 

Air filter restriction has very little to zero effect on fuel economy in gasoline cars with closed loop controlled fuel injection systems. That covers every car on the US market for the last decade.

I don't trust any brochures in a service department, particularly a VW service department. They are there to separate you from your money.

 

OK thank you for that good explanation, my VW is really a Dodge Caravan in disguise. We never talk about the air filter MPG impact here, so I was wondering.

 

There should be some gain since you will be running a thinner oil than before. "Appreciable" is the key word here. I'm with wjtracy. Maybe 2%-3% which is imperceptible to me and within margin of error.

 

I think 2-3% might be a little on the high side. You need to know the actual viscosity of the oil, not the SAE rating. A thick 0W-20 would be a closer to a thin 0W-30 at operating temperature than it would be to a thin 0W-20.

Viscosity at 100C

20 = 5.6 to 9.3 cSt
30 = 9.3 to 12.5 cSt

If you look up their actual kinetic viscosity ranges in SAE J300, 20 weight has lot wider range in percentage than 30 weight
9.3/5.6 = 1.66
12.5/9.3 = 1.34

The HTHS viscosity also has an effect and it isn't necessarily proportional to the
so it's not even that simple.

Short version:
Take any individual claim a of a specific amount of savings with a big grain of salt and a guffaw. The should be a small savings and if you drive consistently and keep good records, you may be able to determine what it is for your driving conditions and the two oils you evaluate.

 

Any appreciable gain with 0w-20 oil?

No.

 

I find an improvement in using 0w-20 oil. Huge gains? no. Worthwhile gains? yes. With UK petrol prices if I only save 1 mpg by using 0w-20 oil, over the life of the oil (10,000 miles) I save the cost of the oil. Does that qualify as an appreciable gain? in my book yes.

The climate in the UK is somewhat cooler than the southern US states and using a "thinner oil" in a cooler climate may make a bigger difference than a hot climate.

 

In racing the guy that makes all the small improvements that are hard to measure or too small to measure is the one that wins, same for fuel economy.

There is no rational reason to doubt that 0W-20 will give a bit better fuel economy then a higher viscosity oil. That's one of the reason I stick with it.

10,000miles/50 mpg = 200.0 US gallons. 10,000 miles/51mpg = 196.1 USg A difference of 3.9 USgallons. Looks like at least the cost of a DIY oil change to me at UK petrol prices.

 

I switched to 0W20 Toyota synthetic oil and I was happy with the result. I don't know if it was the tires that were well worn, or the thinner oil but I noticed an improvement in mpg (in my 08).

 

Give the clean old 5W-30 to a friend with a winter beater.

 

Don't feel guilty changing the Mobil-1 oil at 5000. Toyota said (someone on Prius Chat asked) that it is OK to switch to the lighter 0W-20 for Gen2, but the important thing is to stick with the recommended drain interval. I go 6000 miles with Mobil-1 but believe there may be merit to holding to approx 5 to 6k. I have the extended drain interval Mobil-1 in right now, but subjectively feel engine is louder/valve noise @>5k.

In summer you may not see big effect of lighter lube, but winter in Michigan, I gotta think you will see a MPG benefit for 0W-20.

 

Hi PriusGuy32. Make sure you watch your MPG closely and document any changes. We are all interested in the results.

I just changed from my (thinner) winter fill to my summer fill about a 10 days ago and have been watching really closely for any changes. Both oils are 5W30 but one is a at the lower end of the viscosity range and the other is at the upper end of the range .

Technical data for the "oil heads".

Winter oil: ILSAC GF-5 and Dexos1 rated. Viscosity = 58 cSt @40C, 10.7 cSt @100C. HTHS = 2.9 @150C.

Summer oil: ACEA A3/B4 rated. Viscosity = 72 cSt @40C, 12.2 cSt @100C. HTHS = 3.6 @150C.

As you can see there's a reasonably large change in viscosity between the two (at least as much difference as that between a light 5W30 and a typical 0W20). No change in weather conditions and only one tank on the new oil so far, but here are the preliminary results are <....drum roll.....> no change. The last few tankfuls averaged 57 MPG and the first tankful with the new oil was exactly the same.

Maybe your results will be different due to colder climate PriusGuy. Temperatures have mostly been around 75F to 90F here recently, and will get hotter.

 

Ha, that sounds like a challenge.

Better watch out though, I'm a moving target. I had an easy trip on Sunday so I hypermiled all the way to finish that first tank (on the new oil) at 60 MPG.

 

No flaming me, please, for a mostly oil change question. I'm a newbie.

I have a 2006 Gen II with 93,000 miles. I've changed the oil every 5,000 miles with 5W-30 conventional oil and a Toyota OEM filter. She's running fine. I'm interested in switching over to 0W-20 for increased mileage (maybe) and increased engine life (maybe again). I would continue the change schedule of 5,000 miles, as suggested by Toyota for the Gen II.

Question is this: What are you Gen II homeboys and homegirls using for a filter with your 0W-20 synthetic? Will the Toyota OEM be fine? My guess is yes.

 

Yes the OEM filter will be fine. Several people here are doing 10,000 mile intervals on the OEM filter without any problems.

For your first run on the new oil just keep an eye out for any changes in oil consumption and (as always) be prepared to top off as necessary. This first run on synthetic might also clean a little more aggressively, which can load the filter a bit quicker, so sticking with 5k is probably not a bad idea. After that you could go a little longer than 5k if you want to, but obviously that's up to you.