Oil Viscosity (never-ending debate...)

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Old 03-22-20, 02:27 PM
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Oil Viscosity (never-ending debate...)

There's never any shortage of opinion on the subject of motor oil....but we all (us old timers, that is) agree oils have improved so much in the last 50 years. In 1970, the advise for my Volkswagen Bug was 30 weight Spring and Fall, 20 weight in Winter, 40 weight in July & August, no multi-grades (they weren't well-developed yet) and don't switch to Detergent if Non-Detergent was being used.

Up until my most recent purchase, 5W-20 seemed to be pretty standard for cars made 15 to 30 years ago, but for my recent purchase of a 2012 Scion, the Owner's Manual says use 5W-20 OR 0W-20 for all climates, allowing that the thinner oil will result in slightly better gas mileage. I've not payed attention, but I suspect the quick-lube places probably use 5W-20 by default, but not sure.

I'm guessing the age of the vehicle may suggest using the thicker oil at some point, (I've got 98K miles), or perhaps simply using the thicker in the Summer and the thinner in the Winter.

Y'all's thoughts?
 
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Old 03-22-20, 02:35 PM
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Use thicker oil on a modern engine and you will likely have problems. 50 year old mentality on oil doesn't fly with newer engines today. The tolerances and size of orifices in a modern engine call for thinner oil... thus the switch from 10w40 to 5w20 in many engines today. Thinner oil flows faster. Use thicker oil and the engine cant pump it as fast. Simple as that.

An engine with 98,000 miles is barely broken in.
 
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Old 03-22-20, 04:02 PM
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Why bother when there's this.
 

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Old 03-22-20, 05:19 PM
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Those quick lube places understand liability as well as anyone else and they'll put in what your manufacturer recommends.
 
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Old 03-23-20, 05:42 AM
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Those quick lube places understand liability as well as anyone else and they'll put in what your manufacturer recommends.
This says it all. I see no reason to argue or discuss what oil to use when the manufacture makes the specification.
 
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Old 03-23-20, 06:27 AM
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The fact that improving viscosity will likewise improve mileage is well established but the issue is how much. Studies I've seen put the increase at around 2.5% so each fill-up could see perhaps 10 additional miles. That's not bad but it won't change our lives.

Overall, I agree with previous posts: just go by the owner manual.
 
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Old 03-23-20, 06:41 AM
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It finally registered with me what you are asking when I reread your post. Depending where in the US you live there might be some benefit to using the mfg suggested 0w20 in the winter, but unless its regularly-20F there, I would stick with 5w20 year round.
 
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Old 03-23-20, 06:51 AM
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Back in the 70's when I started learning about auto mechanics as a teenager, we (my family) always used 30 HD in everything.... cars, trucks, tractor (we had a mid 50's Ford 600 4 cyl gas burner)
I didnt start using multi-grade oils until sometime in the 90's ( I think).

I have a 2007 Dodge Ram Hemi with about 210,000+. It does use about 1 - 1 1/2 quarts between 3,000 - 5,000 miles. Because of that, I dont use synthetic oils. Its just my preference. Because of the little bit of oil consumption, I am going to start going back to 3000 mile oil changes, starting this oil change.
1) because when it gets a quart low, I'll just change it.
2) because of the mileage on the engine, I just want to keep a fresher, newer, better quality oil in it.
3) 'cause its what I wanna do.

Personally, I use 10W-30 year around. I live in north Louisiana.
I think the manual calls for 5w-30.
At 210,000+ miles, I think this has worked well for me.
 
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Old 03-23-20, 10:23 AM
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If ever in doubt and you can't find the recommended oil spec, a 5W30 will usually suffice in a pinch. But I would not continue to use it.
 
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Old 03-23-20, 07:08 PM
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Yes I should have made clearer, that both Owners Manual and filler cap state both 0W-20 and 5W-20. "All climates" in the manual. Since we all like better gas mileage, I'm tempted to stick with 0W-20 year round, even tho it gets above 100 degrees in the summer where I live, and occasionally 105 to 107. I just find it interesting the manual encourages 0W-20 for better gas mileage, yet they still give you the choice of the 2 viscosities....they're giving you a clear advantage to use 0W-20 year round, so why include 5W-20 as well, if there's no reason to? My only guess is that 0W-20 may not be as readily available, so they're saying if you can't find that, it's ok to use 5W-20 as well.
 
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Old 03-23-20, 10:11 PM
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there both have a viscosity rating of 20 so really doubt you would notice any difference the winter rating is the viscosity rating at 0 degrees most would just be letting the car idle in the driveway while it warms up a little and are not even driving it immediately when its cold out.
 
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Old 03-24-20, 05:19 AM
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FWIW I use Supertech Synthetic 10w-30 in my tow truck (5.7L Chevy motor) year-round (not much temp variation anyway) and it uses about 1 1/2 quarts in 5k miles. About 325K on the motor, and most of the usage I know is valve guide seals.

I wouldn't sweat the difference between 0w-20 & 5w-20.
 
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Old 03-24-20, 06:31 AM
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My advice to you would vary depending on where you live.
If you were in Detroit I would say one thing and if you are in Miami I would say another.
Having your location as USA makes it difficult to respond to you ....
That being said, your question "Y'all's thoughts?" would prompt me to say go with 5W-20.
 
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Old 03-27-20, 07:00 PM
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Location: North Central Texas, so, very hot in Summer, not too cold in Winter.
 
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Old 03-28-20, 03:58 AM
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As an engineer for one of the big three that used to have release responsibility for global brake fluids, just use what the owners manual states, A lot of time, testing, and validation goes into those recommendations to make it easy for the consumer to know what is best, it's not listed based on a thought and prayer.
 
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Old 03-28-20, 06:32 AM
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Marq1 - I worked at Chrysler Canada in Windsor as a plumber/Pipefitter in the 1960s and spent a lot of time at the "tank farm" where all fluids arrived by rail tank cars and were checked/verified in the lab before being pumped into our storage tanks. We checked a lot of brake fluid building 1000 cars a day
 
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Old 03-29-20, 02:21 PM
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@Marq1 et. al., Not to belabor the point, but those advising to use the specified oil miss my point. TWO viscosities are spec'd, and while there's probably very little difference between them, there must be enough difference for the book to say that 0W-20 will result in better gas mileage. There's no mention of other advantages or disadvantages beyond that, so the implication would be, why bother with 5W-20 if there's no reason to choose it over 0W-20, no matter the climate. Common sense tho would suggest using one in the Summer and the other in Winter, .

I realize this discussion is quite trivial compared to the global crisis at hand, but maybe these trivialities help keep us "normalized" in between depressing news flashes. Y'all be safe.

 
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Old 03-29-20, 04:40 PM
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Common sense tho would suggest using one in the Summer and the other in Winter, .
Yes, so do that. But most people will buy oil based on price and availability. 5W-30 is easier to get than 0w-30. The manufacture is giving you choice. It's like buying 87 octane vs higher octane. My car manuals suggest using the higher octane or premium for a little better mileage. But no harm done using 87. To me a few mpg is not worth the lot extra cents of premium.
 
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