Confused on Oil

[Lucky]

I've been using Castrol 20/50 in my p-car since I got it a little over a year ago. Now I'm wondering how good of an oil Castrol is since some posters recently haven't had good things to say about it.

Since I'm nearing a change and have a DE coming up in 1.5 weeks, I figured I would change oil/filter this weekend. So I bought some Mobil 1 15/50. It's not yet in the engine.

Now I've read some other threads about the "right" way to switch from dino to synthetic with one recommending 3 changes (of Syn) closely spaced (500 to 1500 mi apart).

The Mobil web site says "No special preparation is necessary when switching from conventional oil to Mobil 1."

So my questions are:

Does Castrol suck? Or is it just as good as any other dino oil?

Will all be OK if I tried Mobil 1 and then switched back to dino oil on my next change, or is that a bad practice?

And do I really need to do multiple changes 500, 1000, and 1500 miles apart during the changeover from dino to synthetic?

Thanks in advance for helping an electrical engineer understand all of this mechanical/chemical stuff!

[Doug Zielke]

John, from one Electrical Engineer (who knows next to nothing about petroleum) to another, I'd say Castrol is probably as good as the next dino oil. There are some *premium* dino oils on the market, but if you change often enough you'll probably be ok without them.

As far as Mobil 1 vs Dino compatibility is concerned, the Mobil 1 webpage (and bottle label) says it is totally compatible with *all* other oils. Experiment at will!

[Chuck Moreland]

I've used Castrol 20/50 with excellent results in my '77 for 12 years.

Mobil 1 does claim compatibility. Cars with a front oil cooler can hold about 2 quarts in the cooler and lines that don't drain with an oil change. If you have a front cooler and you really want to get clean, shorten the interval to the second oil change bit.

I think 3 rapid changes is very much overkill.

[Superman]

Changing oil at all those intervals is just as important as making sure the wiper blades are always changed during a full moon. Never a new moon, of course.

Whew!

[dickster]

theres nothing wrong with castrol - i use magnetex(spelling?)

as with any oil the important thing is to change it regular (i do mine on 5k (kilometers))

i don't agree with modern service intervals that suggest you can go up to 18k without a change - it'll be very off color by then (showing signs of breaking down and carbon deposits) i believe you should change it when its still like the "new" color.

mobile 1 would be better for track work etc because it offers more protection at extreme temps, but for road use no real benefit.

[rstoll]

I have been using Castrol 20/50 in all of my cars for 20 yrs. I have compared other peoples opinions to my personal experience. Still using Castrol.

[Oldporsche]

FWIW, I apprenticed in a Foreign Car Repair shop for a couple of years. We used Castrol in everything unless the customer wanted something else. We saw zero problems with Castrol. I personally use Wal-Mart Tech 2000 in all of our personal cars other than one Porsche. The oil is changed in all of the vehicles quarterly because we don't quite put the 3K miles per change. Almost 100% of these miles are short in town trips. We buy the filters by the case. We have never seen an oil related problem in any of our vehicles, chain saws, lawn mower, etc. Its the regular change that's the answer. One of the Porsche's is on Mobile 1 because its not driven very much. The other isn't. Since it is driven in the same manner as the rest of the vehicles, it gets the same regular oil changes with cheap dino oil. I can tell no difference between the performance of the two oils other than the smell when hot.

Good luck,
David Duffield

[911nut]

The greatest advantage to Mobil 1 is it's ability to resist breakdown at 300 degrees F and above. If I was doing DE's with my SC with only the trombone cooler I'd run it. For street driving mineral oils make more sense since it won't get that hot.

I heard about a study performed a long time ago, when engine materials and oils weren't as sophisticated as they are today. Two engines were run side-by-side. One engine had it's oil changed every 3000 miles with the same brand. The other engine recieved an oil change every 7000 miles with the brand switched at every change. The 3000 mile engine showed little wear and had normal oil consumption after 150K miles. The 7000 mile engine was varnished up as a result of the interactions between the various brands of oils and had more wear.

In the end it seems that the most important thing to do with oil is to change it often.

[Leland Pate]

Whats the heaviest weight oil I should run in my car?

[Superman]

I can agree with all I've read here, or at least not disagree. Leland, if I were you I would use an oil that has the number "50" in it, in the summer. In winter I would use something that has a "15" or even a "10" in it. You see, I lived in Boise and I know how cold (minus-something) and how hot (triple digits) it can get. I would be very afraid of those 105 and 110 summer days in clogged Boise traffic. I'd use synthetic, at least in the summer.

I can't disagree with Castrol, but I use Valvoline mostly, and Kendall at times. Love them both. Quaker State used to be good oil but it is not now. Pennzoil is dangerous.

[KFC911]

Hello everyone! This is my first post on this site (although I've been lurking for over 6 months). I've recently acquired my first Porsche (an '88 Commerative Edition Coupe w/ 47K miles), and must admit I'm confused about oil selection. Although the PO used dino oil, I've been contemplating switching to Mobil 1, but have read the caveats about switching to synthetics in 'older cars' (plus the fact that mine doesn't leak a drop, nor does it appear to 'use' any). I live in NC, will put less than 5K miles per year on the car, and will not be racing/DEing the car, so I'm now looking for advice on which type (dino vs. synth), brand, change interval, etc. Thanks in advance...Keith

[pwd72s]

Here in the mild winter temps of the Willamette Valley, I used to run straight SAE 30 Valvoline. Then switched to 20-50 Valvoline. Same weight all year. For the last decade or so, Mobil 1, 15-50, for the heat protection thing, despite never seeing oil temps much above 220. C'mon guys, feel sorry for me.., but living here the problem is getting the car warm enough to open the thermostat, sending oil throught the front cooler. Most of the time, just the engine mounted cooler is enough. Oh, changes of oil weights and brands happened over a long period...1974 through today..BTW, most of the slamming of Castrol? May originate from Bruce Anderson...I listend to him really slam that brand at a Rainbonnet tech seminar. Said he wouldn't even use it in his lawnmower...

[Lucky]

I'm still just a confused EE... but at least I'm feeling a bit better about Castrol. Thanks for the posts with the positive experiences.

I guess I'll use up my current supply of Castrol in the next two changes and then do a permanent switch to Mobil 1, since it looks like switching brands with each change can be a problem due to incompatibility of additive packages.

[carnut169]

More Than You Ever Wanted to Know About Motor Oil
by Ed Hackett (edh@maxey.unr.edu)

--------------------------------------------------------------------------------

Editor's Note: This information appears to have been posted in a public message to rec.motorcycles. I have not been able to verify the accuracy or source for this file.
Choosing the best motor oil is a topic that comes up frequently in discussions between motoheads, whether they are talking about motorcycles or cars. The following article is intended to help you make a choice based on more than the advertising hype.
Oil companies provide data on their oils most often referred to as "typical inspection data". This is an average of the actual physical and a few common chemical properties of their oils. This information is available to the public through their distributors or by writing or calling the company directly. I have compiled a list of the most popular, premium oils so that a ready comparison can be made. If your favorite oil is not on the list get the data from the distributor and use what I have as a data base.

This article is going to look at six of the most important properties of a motor oil readily available to the public: viscosity, viscosity index (VI), flash point, pour point, % sulfated ash, and % zinc.

Viscosity is a measure of the "flowability" of an oil. More specifically, it is the property of an oil to develop and maintain a certain amount of shearing stress dependent on flow, and then to offer continued resistance to flow. Thicker oils generally have a higher viscosity, and thinner oils a lower viscosity. This is the most important property for an engine. An oil with too low a viscosity can shear and loose film strength at high temperatures. An oil with too high a viscosity may not pump to the proper parts at low temperatures and the film may tear at high rpm.

The weights given on oils are arbitrary numbers assigned by the S.A.E. (Society of Automotive Engineers). These numbers correspond to "real" viscosity, as measured by several accepted techniques. These measurements are taken at specific temperatures. Oils that fall into a certain range are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use.

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if it is used. It was not included in this article for that reason. 20W-50 is the same 30 point spread, but because it starts with a heavier base it requires less viscosity index improvers (polymers) to do the job. AMSOIL can formulate their 10W-30 and 15W-40 with no viscosity index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no viscosity improvers in their 5W-30, and I assume the new 10W-30. Follow your manufacturer's recommendations as to which weights are appropriate for your vehicle.

Viscosity Index is an empirical number indicating the rate of change in viscosity of an oil within a given temperature range. Higher numbers indicate a low change, lower numbers indicate a relatively large change. The higher the number the better. This is one major property of an oil that keeps your bearings happy. These numbers can only be compared within a viscosity range. It is not an indication of how well the oil resists thermal breakdown.

Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 F is the minimum to prevent possible high consumption. Flash point is in degrees F.

Pour point is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. This measurement is especially important for oils used in the winter. A borderline pumping temperature is given by some manufacturers. This is the temperature at which the oil will pump and maintain adequate oil pressure. This was not given by a lot of the manufacturers, but seems to be about 20 degrees F above the pour point. The lower the pour point the better. Pour point is in degrees F.

% sulfated ash is how much solid material is left when the oil burns. A high ash content will tend to form more sludge and deposits in the engine. Low ash content also seems to promote long valve life. Look for oils with a low ash content.

% zinc is the amount of zinc used as an extreme pressure, anti- wear additive. The zinc is only used when there is actual metal to metal contact in the engine. Hopefully the oil will do its job and this will rarely occur, but if it does, the zinc compounds react with the metal to prevent scuffing and wear. A level of .11% is enough to protect an automobile engine for the extended oil drain interval, under normal use. Those of you with high revving, air cooled motorcycles or turbo charged cars or bikes might want to look at the oils with the higher zinc content. More doesn't give you better protection, it gives you longer protection if the rate of metal to metal contact is abnormally high. High zinc content can lead to deposit formation and plug fouling.


The synthetics offer the only truly significant differences, due to their superior high temperature oxidation resistance, high film strength, very low tendency to form deposits, stable viscosity base, and low temperature flow characteristics. Synthetics are superior lubricants compared to traditional petroleum oils. You will have to decide if their high cost is justified in your application.

The extended oil drain intervals given by the vehicle manufacturers (typically 7500 miles) and synthetic oil companies (up to 25,000 miles) are for what is called normal service. Normal service is defined as the engine at normal operating temperature, at highway speeds, and in a dust free environment. Stop and go, city driving, trips of less than 10 miles, or extreme heat or cold puts the oil change interval into the severe service category, which is 3000 miles for most vehicles. Synthetics can be run two to three times the mileage of petroleum oils with no problems. They do not react to combustion and combustion by-products to the extent that the dead dinosaur juice does. The longer drain intervals possible help take the bite out of the higher cost of the synthetics. If your car or bike is still under warranty you will have to stick to the recommended drain intervals. These are set for petroleum oils and the manufacturers make no official allowance for the use of synthetics.

Oil additives should not be used. The oil companies have gone to great lengths to develop an additive package that meets the vehicle's requirements. Some of these additives are synergistic, that is the effect of two additives together is greater than the effect of each acting separately. If you add anything to the oil you may upset this balance and prevent the oil from performing to specification.

The numbers above are not, by any means, all there is to determining what makes a top quality oil. The exact base stock used, the type, quality, and quantity of additives used are very important. The given data combined with the manufacturer's claims, your personal experience, and the reputation of the oil among others who use it should help you make an informed choice.

[carnut169]

The Data:
Listed alphabetically --- indicates the data was not available

Brand VI Flash Pour %ash %zinc

20W-50
AMSOIL 136 482 -38 <.5 ---
Castrol GTX 122 440 -15 .85 .12
Exxon High Performance 119 419 -13 .70 .11
Havoline Formula 3 125 465 -30 1.0 ---
Kendall GT-1 129 390 -25 1.0 .16
Pennzoil GT Perf. 120 460 -10 .9 ---
Quaker State Dlx. 155 430 -25 .9 ---
Red Line 150 503 -49 --- ---
Shell Truck Guard 130 450 -15 1.0 .15
Spectro Golden 4 174 440 -35 --- .15
Spectro Golden M.G. 174 440 -35 --- .13
Unocal 121 432 -11 .74 .12
Valvoline All Climate 125 430 -10 1.0 .11
Valvoline Turbo 140 440 -10 .99 .13
Valvoline Race 140 425 -10 1.2 .20
Valvoline Synthetic 146 465 -40 <1.5 .12

20W-40
Castrol Multi-Grade 110 440 -15 .85 .12
Quaker State 121 415 -15 .9 ---

15W-50
Chevron 204 415 -18 .96 .11
Mobil 1 170 470 -55 --- ---
Mystic JT8 144 420 -20 1.7 .15
Red Line 152 503 -49 --- ---

5W-50
Castrol Syntec 180 437 -45 1.2 .10 .095 % Phosphor
Quaker State Synquest 173 457 -76 --- ---
Pennzoil Performax 176 --- -69 --- ---

5W-40
Havoline 170 450 -40 1.4 ---

15W-40
AMSOIL 135 460 -38 <.5 ---
Castrol 134 415 -15 1.3 .14
Chevron Delo 400 136 421 -27 1.0 ---
Exxon XD3 --- 417 -11 .9 .14
Exxon XD3 Extra 135 399 -11 .95 .13
Kendall GT-1 135 410 -25 1.0 .16
Mystic JT8 142 440 -20 1.7 .15
Red Line 149 495 -40 --- ---
Shell Rotella w/XLA 146 410 -25 1.0 .13
Valvoline All Fleet 140 --- -10 1.0 .15
Valvoline Turbo 140 420 -10 .99 .13

10W-30
AMSOIL 142 480 -70 <.5 ---
Castrol GTX 140 415 -33 .85 .12
Chevron Supreme 150 401 -26 .96 .11
Exxon Superflo Hi Perf 135 392 -22 .70 .11
Exxon Superflo Supreme 133 400 -31 .85 .13
Havoline Formula 3 139 430 -30 1.0 ---
Kendall GT-1 139 390 -25 1.0 .16
Mobil 1 160 450 -65 --- ---
Pennzoil PLZ Turbo 140 410 -27 1.0 ---
Quaker State 156 410 -30 .9 ---
Red Line 139 475 -40 --- ---
Shell Fire and Ice 155 410 -35 .9 .12
Shell Super 2000 155 410 -35 1.0 .13
Shell Truck Guard 155 405 -35 1.0 .15
Spectro Golden M.G. 175 405 -40 --- ---
Unocal Super 153 428 -33 .92 .12
Valvoline All Climate 130 410 -26 1.0 .11
Valvoline Turbo 135 410 -26 .99 .13
Valvoline Race 130 410 -26 1.2 .20
Valvoline Synthetic 140 450 -40 <1.5 .12

5W-30
AMSOIL 168 480 -76 <.5 ---
Castrol GTX 156 400 -35 .80 .12
Chevron Supreme 202? 354 -46 .96 .11
Chevron Supreme Synt. 165 446 -72 1.1 .12
Exxon Superflow HP 148 392 -22 .70 .11
Havoline Formula 3 158 420 -40 1.0 ---
Mobil 1 165 445 -65 --- ---
Mystic JT8 161 390 -25 .95 .1
Quaker State 165 405 -35 .9 ---
Red Line 151 455 -49 --- ---
Shell Fire and Ice 167 405 -35 .9 .12
Unocal 151 414 -33 .81 .12
Valvoline All Climate 135 405 -40 1.0 .11
Valvoline Turbo 158 405 -40 .99 .13
Valvoline Synthetic 160 435 -40 <1.5 .12

All of the oils above meet current SG/CD ratings and all vehicle manufacture's warranty requirements in the proper viscosity. All are "good enough", but those with the better numbers are icing on the cake.

[autobonrun]

I've used standard Castrol exclusively in my 79SC for 18 years. At 101k miles we pulled the engine and measured tolerances. The engine was still well within spec with no sludge or buildup. I'm at about 202k miles and the engine still runs strong. The car actually pulls harder now (may have something to do with the SSI's). I use 10/40 in the summer and 5/30 in the winter. Oil is changed every three thousand miles or three months regardless of mileage to remove any moisture or acid buildup from infrequent driving. Since I drive less than 2k miles a year, the three month guideline is the controlling factor. Probably overkill, but I still do it.
I decided not to switch to synthetic on this car.

Until the BMW dealer changed to synthetic oil about 2 years ago, I used standard Castrol in my 93 740iL also. I now use Castrol Synthetic. It does appear that it uses more oil than before but this may just be due to the age.

Interestingly I heard something for the first time today that I assume is a rumor and has no validity. I was purchasing some Castrol Synthetic and the salesman at the parts store told me that mixing oil weights can cause sludge. On oil changes I never completely drain the pan so this statement didn't make much sense. Has anyone else heard this opinion?


'another confused EE'

[Rod Walter]

It's a paradox of oil selection that very few of those who visit this board need worry about the brand of oil chosen yet you are the ones most likely to be concerned! Most people here are so meticulous about changing oil at the appropriate intervals that any of the current SJ rated oils will be just fine.

Using the appropriate weight is probably more important than the brand. This is so that metal-to-metal surfaces are adequately protected both in extreme cold (especially start up) and heat. So if you are concerned pay particular attention to the flash and pour points in Sean's data.

It's the people who figure that since they have to add a quart every 500 miles they don't ever need to change the oil (more importantly, they don't change the filter) that would benefit most from using a higher quality product. But they don't care.

It would be hard to go wrong using any of the current name brand oils. And, Autobonrun, mixing weights won't cause "sludge" - whatever that is (that is to say that the word means too many different things to people to be useful).

[carnut169]

Generally two things cause sludge- Not changing oil frequently enough, and not allowing the engine to warm up- like driving to the mailbox and back only. Also, some engines tend to sludge more easily than others (Toyota V6, like in the RX300 is the very worst, followed by the Land Rover Discovery).

The best regular oils are Amsoil and Red Line.

Look at the numbers:

Amsoil (20-50) 136 482 (-38) <.5

Red Line (20-50) 150 503 (-49) ----

Castrol: (20-50) 122 440 (-15) .85

Mobile1 (15-50) 170 470 (-55) -----

Mobile 1 is better than the rest in all cats except Flash Point- but still stomps every other brand of regular oil. It also has the best score on all the other catagories. Castrol does not really do all that well.

I use Mobile 1 and Porsche oil filters- I change my oil every 3,000 miles and the car does not use or leak any oil in that time. I am sure it is very excessive- but I enjoy it!

[Zeke]

John, I am going to join Doug Z. in saying I don't know much about oils. And I have read a ton on the subject. A lot of the info is very highly technical and proprietary. One thing though, oil companies market blends of synthetic and dino. If you have a little oil left in your system, by that reason it should blend. At least somewhat, given different brands of different bases.

I have 3 four cyl motors here now and God only knows what kind of treatment they have suffered in their service. Sludge was not apparent in any, but contamination was. Clearences weren't too bad, but I've had to grind cranks and replace bearings simply because of scoring from trash in the motor. (And the fact that I'm blueprinting the motor).

I don't know about switching back and forth. I believe that the 911 motor as well as others responds to a little holistic medicine. Treat it well and with consistancy and it will like you better. Is there any one here who doen't believe a clean engine runs better?