0W-30 Oil
 

So, at about 40k miles and for the subsequent 35k miles, my 2016 developed this death rattle right at 3400RPM. Many members here said it was most likely the VVT-i cam mechanism. At first it only happened occasionally (once a tankful) but then gradually became regular and predictable. It usually happened when outside temps were warm, above 75° or so. After perusing some schematics, I thought perhaps loose tolerances so for my last oil change I put in 0W-30, Mobil 1. It's been about 1800 miles since then, temps have been 90-115 degrees and I no longer have the death rattle, at all. Surprisingly (coincidence?), the crickets have disappeared too.
Just thought I'd let you know...

I've been running that oil for about 40k with no problems, I've been pleased.
https://i.imgur.com/JI3IaW8.jpg
I recently switched to 0w40 to give that a try, so far things seem good. I will post those results as well.

Thanks for the info .. :thumbsup:

Back-in-the-day, if a car started burning oil, we would simply put in heavier oil - till we saved up for a set of piston rings...:D


humfrz

And 3 angle valve job. If you did rings without valves, or vice versa, you just immediately blew out the other. Both were required.

I made the same mistake with "make-up" oil. Never heard of the term.

Well, yes, as long as you had the head off, might as well have the valves ground/replaced ... :)

Yes, mill the head, more carburetors, higher lift cam, headers, GMC truck clutch, traction masters .. :thumbup:


humfrz

Also, I just checked my.oil level today. Consumption is practically zero. With the 0W-20, my FRS was using/losing/burning one quart every 3k miles.
Makes me wonder if the engine was actually designed to use something thicker, like 5W-30 (which was so popular with carmakers 10years ago) but was ultimately specced with 0W-20 for fuel savings?

The engine wasn’t designed around 0W-20 since thicker viscosities are allowed by Subaru Japan.

Link?

<-- professional tribologist (friction, wear, and lubrication scientist) with some experience in PCMO additives. If you have a good source, I will gladly vet it and weigh in. I usually stay out of oil stuff as it's tons of hogwash mostly, but viscosity is the first line of defense for a motor and I take it quite seriously.

The 0W20 thing is purely a fuel economy play that is made possible by modern manufacturing practice. 0W30 (if available) would be quite sensible in warmer climates or for track days if within manufacturer's bounds.

I love these two points. :laughabove:


And absolutely agree. One of the reasons why I go for any name brand oil manufacturer that provides the smallest viscosity ranges between the 40 and 100 degrees.

Actually, it works the other way.

The low and high temp viscosities describe a property called Viscosity Index, or VI. VI is the tendency of the material to maintain viscosity over temperature. The basis for VI is 100, and that is for a "normal" oil that loses a "normal" amount of viscosity with a given rise in temperature. A material with a very high VI will not lose as much viscosity over a given temperature interval. Therefore a 15W30 oil behaves like a 15W oil at lower temps and a 30W oil at higher temps. It gains and loses the corresponding amounts of viscosity. A 5W40 oil behaves like a 5W at low temps (less increase in viscosity) and a 40W oil at high temps (less decrease in viscosity). The 5W40 oil experiences less shift in viscosity as the temperature changes in either direction, which is the characteristic behaviour of a high VI oil.

This is why I am not so worried about running a 0W30 oil - it will maintain viscosity at higher temps. A 5W30 oil could get a bit sticky at low temps.

I was under the impression that the higher 40C viscosity causes rougher starts, engine wear, and poorer MPG. As long as the 100C viscosity is comparable to the standards of the suggested weight, then the oil will be good at norm temp. This was my logic behind choosing the tighter range oils within the 0w20 weights. Also, since this reflects the viscosity index, should it go beyond 100 C, it will able to hold the ideal viscosity better than those other 0w20 oils that have a higher 40C viscosity but same 100C viscosity.


My concern was the 0W30 tends to have much higher 40C viscosity (I think they were around 60 cSt, whereas 0W20 have been 45 cSt (and as low as 35). At the 100C 0W30 vs 0W20 are pretty negligible .. like 10 cSt vs 8 cSt. Plus I'd like to stick with the manual's suggestion of 0w20 because my driving is pretty standard public road use.

Remember that you want to maintain a fixed viscosity at all temps. There is a significant drop from 40 to 100 for 15W30. As in, a lot of viscosity loss. Preventing that loss is important. So I look for very high VIs that lose less viscosity over that span and beyond.

I mean, you're welcome to your idea of how it works. Physics doesn't care. :)

It sounds like we're saying the same thing? Less viscosity deviation from what the manufacturers deem to be normal/ideal operating temperatures is what we want.


Since manufacturers suggested 0W20, then I assume they would want a lower viscosity at 40C (as this is much cooler temp than normal operating temperatures thus much more viscous than desirable) and normal standard 100C viscosity of ~8 cSt.


Last I checked our stock car when fully warmed up has oil temps around 100C as well. Thus I looked into the majority 0W20 oils' 100C viscosities and found them all to be ~8 cSt.


The majority of 0w20 at 40C were 44 cSt, but there were two 0w20 oils that were 35/36 cSt. Thus I have decided to use those two oils instead of the other 45 cSt oils.