Why won't this myth die after 30+ years of synthetic oils that are
COMPLETELY compatible with all seal materials used since the 50s and all
As for the original question- you might join the forums on
bobistheoilguy.com and bring it up there. I think the general consensus
is that the Mobil "0wXX" oils have a very good base oil stock and are
typically higher viscosity index (thin less as they get hotter) than the
"5wXX" and "10wXX" versions (whether XX be 30 or 40). So I'd say give
0w40 a try if you want to. There is a subset on there who think Mobil is
overpriced and will recommend Pennzoil Platinum or Castrol Edge... but
any of the 3 are interchangeable in my book. I've had a longer history
with Mobil 1 personally.
If it were me, I'd also seriously consider Shell RotellaT Synthetic
5w40. Its a diesel (really "heavy duty" is more accurate- it also meets
all the gasoline ratings) engine oil and works very well in torquey,
slow-turning engines like big-block v8s. And interestingly, the Subaru
guys who autocross their WRX turbos also love it. I know for a fact that
it doesn't thin out at high temperature as much as Mobil 1 5w30 does,
having tried both in one of my old Mopar 440s. I've been using RotellaT
for about 2 years now.
Completely? That's going overboard. Generally compatible. The POINT is
that when you have been using regular oil there is NO benefit in switching
to synthatic. The fault isn't in the synthetic oil, which is VASTLY superior
to regular oil, but when you have 50,000 miles on an egine that has used
conventional oils you already have the internal parts varnished. Synthetic
do nothing for you. WHen you go from a buck something a quart to 6 bucks a
quart it's stupid.
If you had followed this discussion several of us have suggested Shell
Rotella and Texaco Havoline.
Yes, there is. Synthetic oils can let you extend your oil change
interval even further than you can with conventional oil.
50,000 miles is a drop in the bucket, and if you have varnish or sludge
at 50k you must either a) have a Toyota, or b) have found a stash of
1940s non-detergent oil. Good conventional oils don't "varnish" anything.
The difference between 1 buck for oil you'd damn well better change
every 5000 miles, and 6 bucks per quart for oil that you change every
9000 miles is NEGLIGIBLE in comparison to the other costs of operating
the vehicle. Especially for a rarely-driven car like this which needs
the better acid buffering and moisture tolerance of a top grade oil.
The guy has a 70 Eldorado. Not sure how many times this car has seen 5K,
or this engine. I suspect more than once. I have a new Honda CR-V and use
Castrol Edge. Never used anything but synthetic oil since I got it. The
engine will never see anything else. All conventional oils DO leave some
varnish. Now Pennsylvania oils leave SLUDGE. I'd only use a Pennsylvania oil
in a Russian car that I HATED.
Like a LADA (Fiat) or a Muscovitch. Doesn't make any difference what you use
in those damn things.
Suffice it to say, you're reguritating myths and legends that are 30
years old. Today's "dino" oils are highly refined. Even the most basic
Group II base stocks are so refined that it really doesn't matter where
the original crude came from, the waxes and other contaminants are long
since removed before it gets put in a bottle and sold as motor oil.
Group III+ oils are synthetics derived from petroleum that has gone
through multiple refining steps that basically dismantle the molecules
and put them back together in a very consistent way. Group IV synthetics
are synthesized from natural gas. The idea that there is something
different about "Pennsylvania" motor oil is just a myth, Pennzoil and
Quaker State may have been pretty crappy oils back in the 70s, but today
both of them (even the low-end lines, not just Q or Pennzoil Platinum)
consistently yield some of the best used oil analysis results reported.
Quaker State and Pennzoil are paraffin based. Other oil companies are
asphalt based. Pennsylvania oil is not the idea for today's engines. Which
is why both companies are now heavy into synthetics.
Have you see Castrol's latest data on testing oils? Edge versus everything
Pennzoil "yellow bottle" is not synthetic, yet it consistently yields
superb oil analysis results. I used to be a Pennzoil hater too, but the
facts today say its among the best conventional oils out there. Welcome
to this century, quit living in the previous one.
I could care less about any oil company's self-test results. What
impresses me more is that Castrol Edge does well on independent tests
too. Edge, Pennzoil Platinum, Mobil 1, Valvoline SynPower, etc. are all
Well those that aren't synthetics. That's what both companies packaging
Actually not. SHell Rotella and Taxaco Havoline are considerably better.
I was speaking to the independent tests.. It performs much better than
the other synthetics. Remember,"Edge" is not Castrol's only synthetic, nor
is Mobil One Mobil's only synthetic. Head to head, Edge is the best.
I did read the thread. I saw multiple references to Rotella T
(conventional) 15w40, which is too heavy for anything but a worn-out
beater gasoline engine or an air-cooled gasoline engine. Which is why I
SPECIFICALLY mentioned the synthetic 5w40 version, which gets down much
closer to the 0w40 that the OP asked about. IMO, Rotella synthetic 5w40
will provide all the cold flow he's looking for, but the high VI of the
synthetic Rotella base oil will also protect an engine like a Cad 500
just fine in Death Valley heat if necessary.
Not from ME. Rotella OIL straight weights were made for SEVERE engine use.
(Trucks etc) and are great on cars with high revving engines. I have my own
opinions of what weight to use. Depending on climate. In Wisconsin where I
grew up 10 weight in winter and 30 weight in summer. I don't really believe
in multi-weight oil. We could get into a hot debate on that. I used to work
for Texaco and had fun arguing with the refinery engineers and making them
agree with me that THERE IS REALLY NO SUCH THING. You see, all you do with
multi-weight oils is change the clock. The amount of time it takes to change
the viscosity from what it is at the ambient temperature to run hot. The oil
is still the same - ALL fluids change when heated and cooled. You can't
escape that, just fudge with how long it takes to get from point A to Point
Its obvious that you don't really understand what a "multi weight" oil
means. "The time it takes to change viscosity" doesn't even come into
play at all. All measurements are made with the fluid fully cold or
Yes, all oils change thickness with temperature. But grossly
oversimplyfing- the AMOUNT (not the speed) that a fluids thickness
changes with temperature varies a huge amount from fluid to fluid. The
way that you qualify a fluid to be a "multi weight" oil is to have a
very high viscosity index- meaning that the viscosity change with
temperature is low. A low viscosity index means that thickness changes
greatly with temperature. So whereas a "straight 30 weight" oil may be
as thick as honey at 0 degrees F and as thin as water at 212 F, a 5w40
will be as thick as room-temperature maple syrup at 0F and as thin as
lukewarm syrup at 212F. IOW it doesn't change thickness NEARLY as much,
even after its fully heated or fully cooled and allowed to come to
Example time: How much does the thickness of honey change when you take
it from 40 degrees F to 180 degrees F? A lot. Honey has a low viscosity
index over that temperature change. Now, how much does the thickness of
water change when you take it from 40 degrees F to 180 degrees F? Hardly
at all, in fact not enough to measure without sensitive instruments.
Water has a high VI over that temperature range. You want your engine
oil to behave more like water (although it needs to be thicker) than you
want it to behave like honey.
Making an oil have a high VI used to be done primarily with viscosity
modifiers- long-chain polymers that coil up tightly at low temperatures
letting the fluid flow easily, then uncoil and "tangle" at high
temperatures to thicken the fluid. VI modifiers are used far less these
days since base stock oils are now made with much higher inherent VI.
This is another good reason to use a synthetic in any engine- Rotella T
Synthetic for example is made using Shell's XHVI base fluid (a group
III+ hydroprocessed slack wax derivative) which has a viscosity index
much higher than most conventional oils, and in fact higher than many
Group IV PAO base oils. This means that it can flow easily when cold and
stay thick when hot WITHOUT adding the long coily polymers, which
themselves do not lubricate and in fact contribute to deposit formation
when they break down. This USED to be a good argument for sticking with
a single-grade oil. No more.
These characteristics (high VI base oil, combined with less need for VI
improving polymers) are a good reason to consider a synthetic or
semi-synthetic for any vehicle regardless of age- ESPECIALLY given the
OP's desire for an oil that both flows in cold and protects in heat.
Sure I do. It deflies the LAW of fluids. Look - ther FACT is that at any
given temperature the fluid is constant as far as thickness and lubrication
potential is. It gets thicker when it is cold and thinner when it is hot.
ALL fluids behave that way. All that molecule chaining does is to change the
curve of the change. It modifies time. In other words it stays thicker
longer at higher temperatures.
ALL fluids get thicker when they are cold and thinner when they are HOT.
That includes motor oil. What you do when you screw with the chemistry is
you change the RATE of change over time.In simple terms a multi-weight oil
takes longer to get thin when the engine gets hot, but thin it gets. The
FACT is also that when you deal with a "straight weight" oil - say 30W -
technically it doesn't STAY 30 weight, it THINGS out. But it stays thicker
than a 20 weight. Thinner than a 50 weight. a 10 W. 30 oil supposedly acts
like a 10 weight when hot and a 30 weight when cold. In reality it doesn't
act all that much differently than a 20 weight.
Not really, no.
Look at the viscosity curve. It doesn't have time on any scale. Yes, many
people measure viscosity as a rate of flow through a fixed size hole, but
that doesn't mean there's a T in the definition.
No, not all fluids do this. Some fluids aren't even Newtonian at all.
"C'est un Nagra. C'est suisse, et tres, tres precis."
I had this argument with a refinery engineer almost 30 years ago. We did
measurements together. ALL fluids behave the same way. They get thinner when
they are heated, and thicken when they get colder. It's a law of physics.
Actually it is a measure of the specific DENSITY ot the fluid, and how
it changes at various temperattures.
No, density and viscosity are related but they are not the same thing.
Atactic polypropylene. The molecule is a little ball, but when it gets
hotter, the ball unrolls and the molecule turns into a long straight
string. A solution of the stuff gets thicker when you heat it up, because
the resistance to flow of the unrolled molecule is greater than the
rolled up one.
Typical multigrade motor oils use this principle, although more popular
now are proprietary ester polymers that form corkscrews that unroll
instead of balls. VI technology is pretty nifty stuff.
"C'est un Nagra. C'est suisse, et tres, tres precis."
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.