Quick questions; need answers and opinions.

[Youngblood]

Hey guys, I'm new to the forums but, not new to oil and filters. I find oil and filter research is very interesting.

First a question;

How does oil thicken/thin?
I would imagine the molecular structure rearranges from the temperature differential (heat) to thin to the lower viscosity (correction D189379, sorry was writing two things at once). Can anyone explain this process in-depth?
Sorry, if this question has already been answered. I searched and could not find it.

Now opinions;

Will an engine use oil if you go to a lower viscosity?
I’ve had this happen before and it kind of makes sense.

I have always believed (and I’ve owned foreign and domestic engines) that the only benefit of a 5w30 OEM specification is increased fuel economy sacrificing protection compared to a higher viscosity oil (given that you are in the proper temperature range for the viscosity). I believe that the viscosity difference between 5w30 actually can hurt the combustion cylinders and piston rings to a point. I’ve always ran 10W-30 in my Toyotas because of this reason. I’ve read around the forum and 5w30 for bearing and other clearances makes sense though.

Havoline and Pennzoil.
Is the new formulation of Pennzoil (Purebase) actually any good? Didn’t Pennzoil use to be paraffin based? Paraffin based oils are something to steer clear of.

Also, I’ve read in the forums that people actually like Havoline. I have had nothing but, trouble out of Havoline. I’ve personally cleaned valve train oil galleries because this oil slugdes up so much. Also, it stinks, Any vehicle that uses Havoline you can tell by the smell under the hood as soon as it’s up.

[ February 22, 2006, 12:18 AM: Message edited by: Youngblood ]

 

[D189379]

Oil doesn't thicken as it warms, it thins. And if everything else is equal, a 5w30 will be the exact same viscosity as a 10w30 once it warms up. It just flows better when it's cooled of.

 

[Bryanccfshr]

Isoparaffins are the ultimate hydrocarbon based lube oil structure. Pure Parrafins are free of aromatics and contaminants such as sulfur and include PAO's in their class.

read up. There is enough info here to satisfy your curiosity for a very long time.

 

[Mr Nice]

Do a search of Pennzoil, there is TONS of info.

Both are excellent oils, buy which ever one is lower priced.

 

[Mitch Alsup]

An oil will thicken when the light volitiles evaporate, leaving a more viscous base.

An oil will thin as it picks up and holds onto microscopic particles too small for the filter to remove.

Some engines will consume oils that are too thin for the piston ring package to control and/or when it can be pulled down the valve stem seals and/or pushed out marginal seals.

As most engine wear on most automobile engines occurs in the first several minutes after startup, thinner oils actually protect better than thicker oils, since these thinner oils are closer to operating viscocity for more of the 'trip' on that vehicle.

 

[Curious Kid]

In thinking of how 5w30 might ever harm cylinders or rings as YB put it, probably has to do with deposit formation from the burning/coking of viscosity index improvers (VII) on the piston's ring lands, causing the rings to stick/seize in place on the piston(s) and for them to seal improperly (leading to a down-spiral of potential conditions pertaining to the state of health of the oil over it's OCI...ultimately the state of the engine if not addressed). The more VII's there are in a formulated oil, the greater potential for this to occur in the long run, and with long OCI's. I'd figure today's oils are using higher grades of base oils, having a higher natural VI so as not to require as much VII as previous blends to allow for the same viscosity spread. Some synthetic are said to require little or no VII's.

Correct me if I've been mislead to believe the above as historically true. Thanks.

Enjoy your stay YB.

 

[slalom44]

When an engine is running, full oil pressure will give you "Hydrodynamic Lubrication", which means that there is no metal-to-metal contact within the bearings. Mitch was correct on this. So startups give you boundary and thin-film lubrication which will cause some wear at startup, and a thicker oil takes longer to attain oil pressure. So a thinner oil (within the car manufacturer's specification) is better.

Like you, I used to believe that thicker was better until I joined BITOG.

 

[Youngblood]

Thanks guys, good info.

 

[626LX2.0LATX1998]

Oil thickens (viscous) when it is cold. it thins (flows quickly) when hot.

additives make oil flow for a wider range of temperature, so 0w30, 5w30, 10w30 or SAE 30 flow the same way @ operating temps

SAE 30 will probably not flow @ 0F
10w30 will flow slowly @ 0F
5w30 will flow relatively quicker
0w30 will flow the quickest @ 0F

BUT THEY ARE ALL STILL THICK @ 0F, and NO oil flows quickly @ 0F

 

[GoldenRod]

Well since no one has answered your question, here you go:

Oil has a natural tendency to thin out when it heats up. Multi-viscosity oils counteract this by using long chains of molecules called viscosity index improvers. They are part of the additive package.

When the oil heats up, these long chains of molecules "role out" like sleeping bags; if you will, thus thickening the oil just when it wants to thin down.

That's why a single grade viscosity oil like SAE 30 will thin below a 30W when gets hot and a 10W-30 starts out as a 10W when cold, and then thinkens up to a hot 30W when hot.

So then a straight 30W and a multi-viscisity 10W-30 is the same viscosity (thickness) when hot.

The 10W-30 has the advantage of being a thin 10W when cold. The SAE 30 is a full 30W when cold.

 

[eljefino]

Fear of viscocity index improvers, though reasonable, is a holdover from 1980's oils and earlier.

The group II, II+, and III oils that are blended into modern SM rated 5w30s have a natural tendency toward being multiviscosity anyway. Few if any Viscosity index improvers are needed.

The ripoff is the partial group I 10w30s that sell alongside 5w30s for the same price, though it takes less technology and cheaper basestocks/additives to blend them.

Look up the cst (centistokes-- consider it an "absolute viscosity") of 30 weight oil at 100c operating temp, it'll be around 11. Watch people argue how a 40 weight cuts their power/gas mileage at 15cst. Then look at the cst of your favorite oil at the temp in the morning when you start your car, it could be in the hundreds or even thousands!!

As AEHaas says, "no oil is thin enough at startup".