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I've been using the recommnded weight 0W-20 oil in my 2015 LX (R18 engine] since new. It gets changed every 5k miles.

This last oil change, less than a week ago, at 62k miles, I decided to go with 5W-30, mainly for the 30 part, and not necessarily the 5W part.

I made the switch because I've never thought that 20 wt oil was sufficient for any car for summer temperatures, even in the moderate northeast, where highs can sometimes get into the mid-90s. I've read in multiple places that the general drop in oil viscosity for newer cars is strictly a fuel economy measure. Every little bit helps the OEMs meet the CAFE standards, as is advertising fodder, as well. Every mpg makes a difference, even if it's not real-world accurate.

I noticed almost right away that starting is a little harder. The engine spins just a little longer before lighting off. Idling seems a tad rougher and highway cruising and acceleration seems just a touch laggy.

But if thinner oil is better for fuel economy, shouldn't that mean that it's better for the engine, as well? If my engine is smoother with 0W-20 than 5W--30, shouldn't I be using the prescribed 0W-20?

And which part of the equation is responsible for the smoothness - the 0W/5W, or the 20/30? Would a 0W-30 compromise really be the best bet?

Has anyone here gone off the 0W-20 diet for a heavier oil and experienced similar issues? Has your car run better? No change? Is 20 wt really okay for the long term health of our engines?
 

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I went from 0W-20 to 0W-30. Both Mobil 1 advance fuel economy/extended performance. I didn't feel a difference cranking, nor the engine feeling smoother. I went on a heavier weight purely under the assumption that it should provide a bit better thermal protection for the turbo.

The last time that I've heard somebody saying that their engine felt smoother was when someone I know switched from Mobil 1 to Castro (same weight).

Maybe the R18 behaves differently than the K24
 

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Discussion Starter · #3 ·
Of course I can't draw any conclusions yet, but since your 0W- vis didn't change, it could explain why there was no perceived difference in starting the car. Or maybe not.

I'd also like to hear from folks who changed vis and if there were any changes. Anecdotal evidence doesn't count until there is enough of it, right? :)
 

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This seems like a perfect question for Engineering Explained, if he hasn't done one already.
 
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Discussion Starter · #5 ·
This seems like a perfect question for Engineering Explained, if he hasn't done one already.
I've been through a number of sources re motor oil. Unfortunately, most of them read like religion or politics -- lots of opinion with very little fact. Sometimes, though, you stumble across a blog that actually explains things. The best one I found had to do with flat-tappet engines, which doesn't directly apply to our cars. It was still useful, though. And I'm looking for impressions of oil viscosity changes in our cars, in particular.

I will look up Engineering Explained. Thank you for the lead.
 

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I don't know if the viscosity has anything to do with the chemical properties that enable motor oil to maintain a lubricating film on your engine's moving parts.

We're using 0W20 Mobil 1 HM EP in everything right now (trio of 9th Gen Civics, pair of 8th Gen Accords [I4 & V6], an ancient Gen 2 Acura TL 3.2 Type S, and an even older Gen 2 Odyssey).

In short, on the older cars (TL & Ody), we went from 5W20 to 0W20.

Already finished an entire year, and just finished "spring cleaning 2022," namely changing oil & filters on all seven of them again.

We routinely see temperatures over 110°F in the summer. I just may have some oil samples sent to a lab next year to see if our choice of oil and interval is adequate.

OF
 

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Discussion Starter · #8 ·
in this case, I'd go with the Honda engineers.
All well and good, but I am still hoping for some responses involving real-world experiences with oil viscosity experimentation.
 

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This is a good question for bobistheoilguy forum.

When whatever oil supplier didn’t have the oil I needed, I would go 5-30. For me there was no difference during the summer months. The winter months there is a slight sluggishness when first starting. Once everything was warmed up, it was fine.

If you look at the chart for temp range and oil viscosity, a lot of them overlap. Why Honda chose 0-40 is unknown to me. This is a full synthetic only oil. Did they want their customers to pay more to use full synthetic from them? Idk.


Sent from my iPhone 13 Pro while on the toilet.
 

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I've been advised that 5W-20 helps K series engines with blowby especially on startup. I haven't tried it yet, but I do plan to try it out since I have a 2012 oil burner. I received this advice in response to a question I had about winter viscosity, considering I live in Los Angeles and so my car thinks snow is an old wives' tale. I usually use Kirkland oil, since $30 for ten quarts beats any other benefits, and I just found a Costco near me that sells 5W-20.
 

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Discussion Starter · #11 ·
Now that I have driven the car for a while and have tuned in to how it feels with the 5W-30, I am inclined at this point to try 0W-30 on my next change. That way I can have the cold weather crankability I am used to, and the high temperature protection of 30 wt.
 

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I went from 0W-20 to 0W-30. Both Mobil 1 advance fuel economy/extended performance. I didn't feel a difference cranking, nor the engine feeling smoother. I went on a heavier weight purely under the assumption that it should provide a bit better thermal protection for the turbo.

The last time that I've heard somebody saying that their engine felt smoother was when someone I know switched from Mobil 1 to Castro (same weight).

Maybe the R18 behaves differently than the K24
What's happening is this: the oil is too thick during warmup and too thick when it's warm. You've been running 0w20 in that car since it was brand new. The car is DESIGNED for 0w20 (the tolerances on these motors are fairly tight which is another reason they use a thin oil). If you were going to run something thicker in the summer, you could most likely get away with 5w20 as it's only a tad bit thicker than the oil that is normally used in these.
Now to be quite honest, if the OEM says to run 0w20 year round, don't deviate from that.
 

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I've been using the recommnded weight 0W-20 oil in my 2015 LX (R18 engine] since new. It gets changed every 5k miles.

This last oil change, less than a week ago, at 62k miles, I decided to go with 5W-30, mainly for the 30 part, and not necessarily the 5W part.

I made the switch because I've never thought that 20 wt oil was sufficient for any car for summer temperatures, even in the moderate northeast, where highs can sometimes get into the mid-90s. I've read in multiple places that the general drop in oil viscosity for newer cars is strictly a fuel economy measure. Every little bit helps the OEMs meet the CAFE standards, as is advertising fodder, as well. Every mpg makes a difference, even if it's not real-world accurate.

I noticed almost right away that starting is a little harder. The engine spins just a little longer before lighting off. Idling seems a tad rougher and highway cruising and acceleration seems just a touch laggy.

But if thinner oil is better for fuel economy, shouldn't that mean that it's better for the engine, as well? If my engine is smoother with 0W-20 than 5W--30, shouldn't I be using the prescribed 0W-20?

And which part of the equation is responsible for the smoothness - the 0W/5W, or the 20/30? Would a 0W-30 compromise really be the best bet?

Has anyone here gone off the 0W-20 diet for a heavier oil and experienced similar issues? Has your car run better? No change? Is 20 wt really okay for the long term health of our engines?
I would stick to oem weight in N/A cars that aren’t track use. I use ams signature 5w-30 in a turbo k24z7 which has been the best performer so far. Royal purple 5w-30 was next in line. I would stick to 0w-20 and just use a better oil like royal purple or ams. There’s a lot of independent testing data on ams signature series that shows it holds up much better than all the other oils. That’s why I switched from royal purple.
 

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Discussion Starter · #14 ·
What's happening is this: the oil is too thick during warmup and too thick when it's warm. You've been running 0w20 in that car since it was brand new. The car is DESIGNED for 0w20 (the tolerances on these motors are fairly tight which is another reason they use a thin oil). If you were going to run something thicker in the summer, you could most likely get away with 5w20 as it's only a tad bit thicker than the oil that is normally used in these.
Now to be quite honest, if the OEM says to run 0w20 year round, don't deviate from that.
So you're saying that 5W-20 is better in hot weather than 0W-30?

I would think that the extra protection of a 30 wt (over a 20 wt) would be better for when the engine is up to full operating temperature, and a 0W better than a 5W at startup when the engine and oil are cold (even 80*F is cold for engines and motor oils).

If I were to run a 20 wt oil, I would go back to 0W-20 for the cold starting advantage.
 

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I started looking through some of my shop manuals, both new and old, regarding crankshaft rod and main bearing clearances.

In general, I found that older engines with much more generous bearing service clearances could use 10W40 oils and still ensure reliable pressurized oil flow characteristics.

New Hondas have fairly tight crankshaft rod bearing and main bearing clearances. I just opened up my Gen 8 Accord shop manual to compare against a Fiat 2000 twin-cam I4 (1980's, but designed in the late 60's ... this engine platform has won more WRC championships than any other design).

The minimum clearance for the Honda (0.017 inches) is about half of that for the Fiat (0.030 inches). The Fiat could use 10W40 oils, and I'd even heard of people using 20W50 to minimize leaking past old valve seals. No way could you, or should you ever use those oil viscosity grades in a newer Honda...it's got only half of the cross-sectional area available to supply oil for crank oil passages that lead to the crank rod bearings.

I would think that the extra protection of a 30 wt (over a 20 wt) would be better for when the engine is up to full operating temperature
The name of the game is to be able to flow the proper viscosity oil through the oil galleries and into the crankshaft bearings (as an example) so that the bearings remain hydrodynamic (pressurized film of oil). Thicker viscosity oil will result in a pressure drop and flow decrease through the passages in the crank that feed the rod bearing journals.

I would stick to oem weight in N/A cars that aren’t track use. I use ams signature 5w-30 in a turbo k24z7 which has been the best performer so far. Royal purple 5w-30 was next in line. I would stick to 0w-20 and just use a better oil like royal purple or ams. There’s a lot of independent testing data on ams signature series that shows it holds up much better than all the other oils. That’s why I switched from royal purple.
This.

OF
 

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Discussion Starter · #16 ·
So I just now changed my oil back to 0W-20. The 5W-30 was in there just under a month. Almost new!

I'm gonna hang onto the 5W-30 for my VW, which sees a few hundred miles a year.
 

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Has anyone made the switch from (SAE 0W-20) Mobil-1 Advanced Fuel Economy Fully Synthetic Oil to (SAE 0W-16) Mobil-1 Advanced Fuel Economy Fully Synthetic Ultra-Low Viscosity Oil and noticed an increase in fuel millage MPG?

The ILSAC GF-6 was split into two subcategories: GF-6A and GF-6B. The principal difference between the two subcategories of oils concerns viscosity grade and high temperature, high shear (HTHS) performance. The ILSAC GF-6B grade will provide the same performance as GF-6A, but with the added aim of lower HTHS to deliver potential further fuel economy benefits and the ILSAC GF-6B will be defined for 0W-16 viscosity grade oils only.

They state ILSAC GF-6A is backward compatible, while ILSAC GF-6B will not be backward compatible for older applications and features an entirely new formulation. In addition to GF-6B’s lower viscosity, a unique balance of additives, viscosity modifiers and base oils will work with new and unique engine designs to maximize fuel economy.



 

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Has anyone made the switch from (SAE 0W-20) Mobil-1 Advanced Fuel Economy Fully Synthetic Oil to (SAE 0W-16) Mobil-1 Advanced Fuel Economy Fully Synthetic Ultra-Low Viscosity Oil and noticed an increase in fuel millage MPG?
No, not us. Every Honda / Acura we own or maintain uses “20” for the operating temperature viscosity … so we’re staying with that.

in this case, I'd go with the Honda engineers.
Me, too.

Yeah let Honda do the experimenting rather than experimenting on your own car just stick with what Honda saids works best IMO.
Same here.

If we get something newer that specifies 0W16, then that’s what we’ll use.

OF
 
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