Motor Oil Viscosity?

**CharlesW** · 10-17-2005, 02:47 PM

How about some discussion on oil viscosity?
Please comment no matter if you use synthetic or conventional, but please mention which variety you are commenting on.
Experiences would be great, but opinions would be interesting, too.
I happen to be using Quaker State full synthetic.

1. How many believe in 5W-20,30 whatever? The reason I ask is that I read on "Bob is The Oil Guy" that many people consider 5W oil to be strictly for fuel economy and not really the best for your motor. One individual went so far as to describe 5W-20 as "cutting oil".

2. To me, 10W-30 seems to be a pretty good compromise. 130,000, 140,000, 152,000 and 168,00 on a few vehicles kind of reinforces that feeling.

3. Anyone believe in mixing viscosities of the same brand and type of oil.

4. How about needing to add oil and only having 5W-20 to add to a motor with 10W-30 in it?

5. How about having only 10W-30 to add to a motor with 5W-20/30 in it.

6. I think most any oil would be better than being low on oil, but would you feel that you would need to change it as soon as you could?

Comments, questions, opinions?

Charles

**tubafeak** · 10-17-2005, 03:41 PM

I use Castrol GTX High Mileage every 4000 or so in both of my cars (every 6 months or so). 5W-30 for both the taurus and the honda. never had any oil related problems. If I had gottent eh cars earlier in their lives I would be using Mobil 1 synthetic (or Royal Purple in the CRX if I do a motor swap/rebuild) but as I got both cars with more than 100k on the clock I`m not sure if the rings are seated correctly and you don`t want to use synthetic exclusively in a car that eats oil. The GTX has been pretty good about not allowing oil burn off. As for viscosity, I think that with Dino oil the weight means more. If your car needs 5W-2 then that`s the dino oil you should use. Synthertics are much lighter than dino oil (from my highly calibrated test of rubbing in between my thumb and forefinger), if you`re racing your car at all go up a viscosity level, it will protect the engine better and you won`t lose a lot of power if it`s a synthetic oil.

As for tranny fills, go with a high quality synthetic (Redline, Royal Purple, something that you have to go to a speed shop to find), you won`t be changing these fluids for a while so you might as well get the good stuff in there. I switched from whatever was in the tranny of my CRX to Redline 10W-40 and the shifting became so much easier and smoother (is that a word?).

The bottom line, whatever your manual says is what you should go with, I know someone who put 15W-50 in to a Prius, it wasn`t pretty because that engine is designed for 0W (what, we got bored :noexpress

hmy: :evil: ).

**onemeanmachine** · 10-17-2005, 03:47 PM

I`ll throw in my 2 cents:
1. I use 5w30 in my truck because I`d rather know my oil is getting back up to the rockers quickly than worry about how quickly it drains off of them. My cousin and I both use Amsoil synthetic 5w30, and it holds up better than any other oil I`ve used...we both change filters at 12.5k miles and oil at around 25k...yep 25,000! As testament to it`s quality my cousin has 225k on his truck and countless hours on all his construction eqpt. which also use Amsoil, and hasn`t had a problem to date. And if anyone can punish an engine it`s my cousin and I!
2. I`ve always believed that 10w30 is a good oil for engines over 75k, but I`ll only change if I start to burn any oil...that`s about all the extra viscosity is good for unless you`re really gonna beat on your car.
3-6. I definitely wouldn`t recommend mixing viscosities for any reason, but obviously in an emergency I`m more inclined to add a different oil to get me home rather than ruin my engine (it`s a lot cheaper to change oil than change engines!). I would be changing my oil as soon as possible though.

**Don** · 10-22-2005, 05:23 AM

I run 0W23 or 5W30 Mobile 1 oil all year in my car. The "0" is the indicator of how well the oil flows cold, and the 30 is the viscosity at operating temp.

Having an oil with a low number for the first number in the series is better for the engine particularly during cold starts because a low numbered oil will reach the upper end of the engine more quickly, lowering the time of minimal lubrication/maximum wear an engine experiences at start up.

**CharlesW** · 10-22-2005, 06:53 AM

Originally Posted by Don

I run 0W23 or 5W30 Mobile 1 oil all year in my car. The "0" is the indicator of how well the oil flows cold, and the 30 is the viscosity at operating temp.

Having an oil with a low number for the first number in the series is better for the engine particularly during cold starts because a low numbered oil will reach the upper end of the engine more quickly, lowering the time of minimal lubrication/maximum wear an engine experiences at start up.

What the numbers mean is no problem. What I`m curious about is what happens under actual running conditions.
There has to be additives in the oil that cause the change in viscosity when it gets hot. In fact, I think I have read where they use "polymers".

Those polymers are supposed to get thicker when heated causing the change in viscosity.
There seems to be some thought that the polymers are thickeners and don`t lubricate, just thicken. Wider viscosity ranges, more polymers that don`t lubricate. There is also some debate about the polymers breaking down during the time they are doing their job. Like maybe they would be 5W-30 for some time, then deteriorate and have a lower viscosity rating at the higher temperatures.
It gets a little like wax/sealant discussions. Lots of ideas and opinions, but not a lot of true, hard facts.

Charles

**Don** · 10-22-2005, 08:11 PM

Originally Posted by CharlesW

There seems to be some thought that the polymers are thickeners and don`t lubricate, just thicken. Wider viscosity ranges, more polymers that don`t lubricate. .

Charles

I DO know that having a multi-vis oil with widely separated numbers IE 5W50 is not a good thing because of the amounts of additives it takes to make an oil with such a wide range

**Monty_Merlot** · 10-23-2005, 06:22 AM

Use the viscosity recommended by your owners manual. Each automaker doesn`t pull these figures out of the air - they pick them for specific reasons. Both Ford & Honda started recommending 5W20 back in 2001, and if there were adverse effects on their respective engine durability, we would have seen that by now. What have we seen? Chrysler begin recommending that oil weight, 5W20, specifically for their multi-displacement Hemi V-8. Multi-displacement won`t work properly with 5W30.

Use the weight recommended by your owners manual.

**JaCkaL829** · 10-23-2005, 09:09 AM

Originally Posted by Monty_Merlot

Use the viscosity recommended by your owners manual. Each automaker doesn`t pull these figures out of the air - they pick them for specific reasons. Both Ford & Honda started recommending 5W20 back in 2001, and if there were adverse effects on their respective engine durability, we would have seen that by now. What have we seen? Chrysler begin recommending that oil weight, 5W20, specifically for their multi-displacement Hemi V-8. Multi-displacement won`t work properly with 5W30.

Use the weight recommended by your owners manual.

I`ve actually read from a couple different people that 5W-20 doesn`t protect as well as other oils, the main reason more and more companies are using it, is to boost MPG ratings. Whether or not there is validity to that claim, I have no idea, i`m no car engineer or chemist.
My Acura recommends 5W-20 and since I still have a warranty on it, I will use it but it kinda makes me raise an eyebrow at how well its protecting my engine. I do plan on switching to Mobil 1 next oil change so maybe that will help.

**RTexasF** · 10-23-2005, 09:57 AM

I use Mobil 1 0W20 (no longer available) in my `04 Accord and M1 5W30 in the `03 Corolla.

While it`s true that the 5W20 oils are for higher MPG they are consistantly showing excellent in used oil analysis. Here is some terrific reading:

http://theoildrop.server101.com/cgi/...=0;DaysPrune=0

Both cars go 7500 miles per oil change now. Once I`ve run out of 0W20 (still have a 30 quart stash), I`ll go to Mobil 1 5W30 EP and change @10K-12K intervals for both cars.

**JaCkaL829** · 10-23-2005, 01:36 PM

RTexas: Any particular reason for not using the new M1 5W-20 now? You said you used 0W-20 now your going to 5W-30?

**Monty_Merlot** · 10-23-2005, 02:21 PM

Originally Posted by JaCkaL829

I`ve actually read from a couple different people that 5W-20 doesn`t protect as well as other oils, the main reason more and more companies are using it, is to boost MPG ratings. Whether or not there is validity to that claim, I have no idea, i`m no car engineer or chemist.
My Acura recommends 5W-20 and since I still have a warranty on it, I will use it but it kinda makes me raise an eyebrow at how well its protecting my engine. I do plan on switching to Mobil 1 next oil change so maybe that will help.

Yea, I was concerned at first, but since it`s been in use, there haven`t been any reported problems from it that I`m aware. Plus, the Motorcraft 5W20, a semi-synthetic, has been showing some impressive results in terms of used oil analysis.

**jaybs02** · 10-23-2005, 03:20 PM

I actualy use whatever they put in at the "quick lube" normally they use 10w30 and I believe that Ford recommened 5w30 for my Taurus, so I guess it`s close enough

"J"

**CharlesW** · 10-23-2005, 04:31 PM

Originally Posted by jaybs95

I actualy use whatever they put in at the "quick lube" normally they use 10w30 and I believe that Ford recommened 5w30 for my Taurus, so I guess it`s close enough

"J"

Most "quick lubes" in my area will use whatever viscosity you tell them. Many will even use the oil you specify for an extra charge. If you want synthetic, that would also be an additional charge.

Charles

**tubafeak** · 10-23-2005, 05:47 PM

I used to work at a quick lube place, if you ask for a specific viscosity they`ll put it in for you. The trick is actually asking for it. Also, if you don`t ask they`ll fill your tires to sidewall spec (great for drifting, not great for driving.

**RTexasF** · 10-26-2005, 12:02 PM

Originally Posted by JaCkaL829

RTexas: Any particular reason for not using the new M1 5W-20 now? You said you used 0W-20 now your going to 5W-30?

since I have a fair amount of the "0" in stock, there`s no reason to change.

M1`s 30 weight oils are just barely a 30 weight and I can go longer without an oil change using the EP.