engine viscosity

[Grant L. Meredith]

Hi , was thinking 20W/50 for my 1928, Dad thinks too heavy more like a 10W/40 should be used.  Thoughts?

[C Carl]

Is it an old higher mileage engine , or a recently rebuilt one ? Do you drive in a hotter climate , or a cooler one ? Is most of your driving  at touring speeds , or slow , or parade speeds ? What oil are you using now , with what oil pressure , fully warmed up , at idle and at speed ?   - Carl

[Mark Shaw]

20w/40 should be all you need if your oil pressure stays above 15 psi during idle on a warm day. 

 

If not, you need to rebuild your oil pump. 

 

If that doesn't work, check your engine bearings for excessive wear.

 

[Janousek]

Straight 40 wt is what I use in our 31'.   30wt or 10-40 at hot idle was pretty low on pressure.   Straight 40wt keeps it at 5psi at hot idle.  

[trimacar]

I use straight 30 weight in my cars, since they are driven mostly in mild weather, so I agree with Janousek on the use.  However, with engine hot, the 10W-40 should be acting like a heavy weight oil.

 

As to basics, a 10W-40, for example, has the characteristics of a 10 weight oil at low temperature, and characteristics of a 40 weight oil at 100 degrees Centigrade, 212 degrees F....

 

Thus, in cold weather, the oil acts as if it's "thinner" and flows better, making for easier starting and more flow to the bearings.

 

I'd use straight 30 weight if engine is in good condition, possibly straight 40 weight if there's known wear on the engine.

[FLYER15015]

Grant,

You need to provide a LOT MORE INFO, such as the questions Carl asked, before you can expect a proper answer !!!

 

FYI in my '40 LTD that has never had the head off and 50K+ on the clock, I run a "witches brew" of Shell Rotella 10-40, STP, ZDDP and Restore in my crank case.

 

Of course I pulled the pan and sanded the oil pump's bottom plate, that was leaking badly, a inserted a 1/4" nut behind the pressure relief spring.

 

Results are 60# at start up, 30 at HOT idle and 40# cruzin at 55MPH, and all with "unmolested" rings and bearings.

 

She still burns a quart in about 600 miles, and we get some blue smoke on those long downhill mountain grades. Adds character to the trip.

 

Mike in Colorado

Edited May 26, 2017 by FLYER15015 (see edit history)

[27donb]

20w-50 in my 27-25 and 27-54CC engines with no issues.

[dracenroc]

I'm using a unalloyed 40wt  with oxidation inhibitors and pour point improvers. Engine unmodified with original oil filter, midrange weather conditions

[Janousek]

Multi weights in our 31' don't act like a straight weight when hot.   Oil pressure at hot idle is low.  Our 35' Auburn is the same way.  10-40 was barely noticable over 10-30 on the gage.  30 or 40 weight carry better oil pressure hot.   I run them in warmer weather so their isn't a need for multi weights.  I use Schaeffer's racing oil or Brad Penn without any additives.  I used to run reg oil with zinc added but I can buy a 5 gallon pail of the correct oil for less money than trying to be chemist.  

 

Straight 40 just acts right in our cars and other cars I service.    Rule of thumb from a long time antique engine builder is 10psi per 1000 rpm's.  

 

Getting into the 40's the cars started carrying more oil pressure than the 20-30's.  You can't go wrong with 30 or 40 wt straight in an old car.  

[Grant L. Meredith]

the car with 10w40 holds easy 15psi oil pressure when fully warmed.  Engine I'm told had 600 miles after a complete rebuild.  I'm approx. it now is under at 800 miles.  I just want to protect the engine . I have no details on how it was built. 

[C Carl]

If you have 15 at idle fully warmed up on 10W/40 , stay with it. Use conventional oil for another 4000 miles. At that point go to full synthetic. Some synthetics are better (more synthetic) , than others. Use Mobil 1 or better. I am now using Amsoil in my '24 and '27 Cadillacs. Amsoil is extremely synthetic , and a fairly recent formulation of it has plenty of zinc and phosphorus for our old engines. There is a school of thought which regards the superior lubricating characteristics of synthetics as superfluous overkill in our old low output slow turning engines. All engines have hotspots , and all engines are vulnerable to emergency overheat mishaps. I , as you do , want to give my engines the best protection available. The reason to use conventional oil for the first 4 - 5000 miles in a newly overhauled engine , is that synthetic lubricates so well , that you will not polish out the cylinder wall hone marks with it. There is that true , true saying that the worst oil today lubricates better than the best oil 80 , 90 , 100 years ago. I don't see too many people with old hobby cars ,out in perpetual search for the worst oil they can find today. True , true saying : ANY full synthetic oil today lubricates better than the best conventional goo. Oh , and while we are talking lubricants , use synthetic grease also. Dad was right.   - Carl

 

P.S. : You know everyone here would love to see pics of all aspects of your '28 Buick.  Thanks !   - CC

[Grimy]

My good friend Carl is a very fervent disciple of synthetic oil.  Despite synthetic's many advantages, I stay with dino oil for the following reasons:  Some of the contaminants produced by internal combustion engines are LIQUID (acids and water), and the only way to get rid of them is to drain the oil, although long hot runs are good for getting water out.  Moreover, the dispersant/detergent additives in oil become depleted by oxidation (via exposure to air) as well as by mileage.  For most of us, our collector cars don't get nearly as much exercise as our modern iron, for which synthetics are more suitable.  I prefer to change oil once a year, usually in the fall at the end of the major driving season, irrespective of mileage. 

 

Of course, opinions are like bellybuttons....

[C Carl]

Although synthetic oil can be used in some applications , under certain conditions , virtually forever by monitoring with regular oil analysis , I do not advocate for this in our old engines. Indeed blowby , fuel dilution , and perhaps more degradation must be factored into oil change frequency. I am willing to treat my engines to the very best lubrication petroleum engineering can provide. If I have to recycle $75 worth of oil rather than $30 worth of oil once a year , $45 seems like cheap insurance. One , just ONE incident of having one of your engines survive accidental overheat due to having had the extra protection synthetic gives under such conditions , will have you at the pulpit preaching Syntheticism yourselves , My Dear Brothers ! Penitence in hopes of Absolution will be the path for he who weeps , wails , and gnashes teeth , suffering the torments and agony from an engine fried in dinosaur lard. Peace Be Upon You.  - Carl

[Grimy]

5 minutes ago, C Carl said:

just ONE incident of having one of your engines survive accidental overheat due to having had the extra protection synthetic gives under such conditions

Carl, I pay close and constant attention to my oil pressure and coolant temp gauges, and haven't fried an engine yet in almost 60 years, but have come close. 

 

I lost a 1.5 inch core plug --it fell out completely!--from the center of the right bank of a 1964 Cad 429 at 70mph on the Atlanta Beltway in 1971.  Fortunately there was an immediate off-ramp and a real service station at the bottom of the ramp.  Disconnected the battery quickly because the insulation on the lead to the starter had melted (taped it up as a quick fix).  It was 2.5 hrs before the engine cooled enough to even approach the engine.  Removed RF wheel and inner fender panel, and a long extension gave enough reach to pound the new plug home.  I was certain I'd fried the bearings or cracked the head or block, or at least blown a head gasket.  I was the luckiest guy in Georgia that day as there were no ill effects, and I drove that car another 70k miles without pulling the heads or pan.  Oil was Havoline HD-30.

 

It might be difficult to quantify how many additional seconds synthetic would give you vs. dino oil.... :-)

[C Carl]

George , from the short interval between my laboriously thumb tapped posting , and your response , I calculate your stenographic skills at about the 140 w.p.m. level. Is that correct ? Coming up is my hot Cadillac incident which I have written about over on CLC forums. Not sure whether AACA has been treated to it yet. O.K. , back to the thumbs. - CC

[Grimy]

Carl, I type with only my two forefingers. Sophomore year in college (1961-62) I took very complete notes for a mandatory American History course and typed them up on dittomasters on my Smith-Corona portable typewriter.  Sold subscriptions to other students, which kept me in beer money and gas. Dittomasters required a lot of finger pressure.  Typing instructor in the Army a few years later told me I was the only student she'd failed to teach 10-finger typing.  I'm good for about 25 wpm, no better than that, which was enough to pass the typing course.

 

Looking forward to your Cadillac tale.  I was aware of the --er, irony-- that my story also involved a Cadillac, albeit newer.

 

I may not see, or reply to, your missive tonight, and I'm about to take the elderly (16.5) dog out for his last tour, then hit the sack.  God willing, I'll be back tomorrow.

 

Different strokes for different folks!  Each has a rationale for his choices, which is a good thing!  Thanks for adding the issue of fuel dilution of motor oil, a definite concern in the cars you and I drive.  be sure to stop by on your way to retrieve your Cad sedan from Lost Wages.

[C Carl]

I bought a sleeping beauty out of Port Washington , Long Island , N.Y. over 30 years ago. Just an 8 or so year old lightly used car. A ''76 Eldo conv which Sandy and I used to cruise New England to celebrate her birthday (Sept. 24) , and gorgeous leaves in abundance that time of year. With only 22,000 miles on the clock , it had obviously been dormant from time to time. Fall , Winter , Spring , cool , cool , cool. So. Cal Summer , HOT , HOT , HOT ! Now , I believe I am capable of driving these big FWD beasts as fast and aggressively as anyone in the world. I used to enjoy it , too , particularly when I could disprove the commonly held doctrine that these hogs can't  handle. Ask those guys I overtook and passed back in '79 in my gold '71 Eldo conv , top down , coming North up the now slide closed Hwy 1. Red Dino , red Cobra. Dicing skillfully and swiftly. Granted , they had their ladies by their sides necessitating restraint. My lady love driving her own car , had accidentally fallen out of formation , and missed the 1 exit off 101 and I didn't realize it until too late do do anything other than FLAT OUT GET IT ON !!!! , later to catch her after she had come about , at the first stop light Northbound , there just after Carmel , by the Chevron station. Granted. Driving with delicate passengers , they had sanitary considerations which I , driving solo , did not. So they maintained proper lane position , which I ignored any time I had the opportunity to do so in order to straighten out a curve , or a set of several of 'em. I had come up on them after seeing them exit a very long hairpin which I was just entering. So I slipstreamed them (they were not exactly hanging about either) , until opportunity presented itself. If you are interested in knowing the dynamics of how I overtook them , call , or wait until I see you. Committing this maneuver to public print could have serious negative repercussions to me , as you would have had to be there to understand how safe , though shocking , this change of position was done. The next day , by coincidence , I encountered the Cobra driver at the entrance to Laguna Seca. He knew what had happened , and how properly and creatively it was done. He was in the perfect position to watch and gasp ! The look on his face and admiring tip of the hat ................... It  is not inconceivable that those guys could be found. They would be about your age , George. This took place in 1979. 

 

The above is to present credentials , and give some scale to my velocity and punishing driving modes to which I occasionally succumbed in my alert and strong youth. I also held a couple of unofficial Andean speed records considered impossible 40 or so years ago. I was the driver of choice for recreational Embassy joint jaunts in Ecuador , where my point A to point B abilities were subject of some admiration. Obviously , though fast , I was never asked to slow down by British or U.S. Embassy personnel. (By the way if any of you had the great good fortune to have been in Quito during the days of OPEC dominance 40 years ago , and a strong Sucre , the Ecuadorean currency , you will recall our fearless , peerless leader , Alan of the British Embassy , who at an incredibly tough young 57 back then , cruised the streets in his Rolls-Royce Phantom 2 Continental Town Car. Remember ?)  Anyway , all this being said ,  several years after the '71 Eldo event , a merciless motivation in the aforementioned , low mileage '76 Eldo droptop took place. The one which had experienced long periods of slumber. Radiators don't like that , as we all know. VERY hot , hard summer driving , now for the first time ever. Got hot quickly , and then much hotter yet. The munged-up cooling system could not handle it. Temp light on , I nosed it into the wind , stopped , and kept it running in park. Tinkle , tinkle , crackle , crackle. If it had been night , you would have seen the ex manifolds glowing red. They both cracked. I had a full charge of Valvoline 20W/50 Synthetic in it. I have put scores of thousands of miles on it since , no problems. Replaced the radiator , and the ex manifolds. Naturally still run synthetic. Oh what fun I had with a couple of Cadillacs I still own , now AACA Antiques ! 

 

I have a notification you have posted while I slowly tapped and slogged out this revelation you have provoked in me , George. I shall post this now  , before I think better of such self incrimination , and delete this babble. A few more seconds ? WITHOUT A DOUBT ! That is what high flashpoint is all about !   - Carl

Edited December 31, 2017 by C Carl
Minor clerical details (see edit history)

[C Carl]

Now that you are taking your rest , I can say that when you read this , it will be apropriate to say : Good morning , George , and all ! Yeah , it is certain that if those two drivers of the red cars have attained old age sound of mind , they will still recall the thrill of it all , and the puckering they must have involuntarily experienced as they were left behind by a mere '71 Eldo on a straightaway upon which Angles  feared to zoom at speed that afternoon. I know it is a multi-million to one chance that someone reading this witnessed the event , but the odds are greater than zero. If you are the gentleman who enjoyed it from the drivers seat of the only oncoming vehicle , the motorhome , a tip of the hat to YOU ! And you are quite welcome to what must have been great entertainment ! Courtesy of  : Cadillac Carl              (As I say , I reckon in my prime I could propel those stocker monsters as fast as anyone in the world. And the red car boys had no idea whether some Indy driver , or Sir Stirling might have been at the wheel ! Yeah , the look on his admiring face the next day !)

[Spinneyhill]

Just a note about how long an engine will run after the oil is drained. I have seen "cage" tests where the oil and water is drained from an engine and then it is run full throttle until seizure. Raffle tickets are sold for your guess at how long it will run. The engines lasted 20 to 30 minutes before slowing and dying.

 

As Carl says, the best protection is with full synthetic oil. Wear tests show almost no wear on many full synthetic oils and pretty much all full synthetic oils are better than all mineral oils at minimising wear.

 

As regards multi-grades, the whole point of it is that the oil behaves as a thinner oil (e.g. SAE 5 or 10) at startup with a cold engine. By far most wear occurs at startup with cold engine and poor oil circulation until the oil is pumped around, esp. with a "thick" oil (mono-grade or a multi- with a high W grade). Thinner oils are far easier to pump and full circulation is achieved more rapidly than with thicker oils.

 

I have better and more consistent oil pressure with 5W-40 semi-synthetic than with 20W-50 mineral oil in my 1930 Dodge Brothers Eight.

 

Whatever oil you chose, don't bother adding STP. It is a viscosifier and will thicken the oil. You go to a lot of trouble to work out which grade to use then you mess it up by a more-or-less unknown amount by adding a thickener. Why? It is unnecessary and probably deleterious.

 

If you want maximum zinc, use a CI rated diesel oil. If you use a synthetic oil, don't bother adding zinc. They all have enough and the wear minimising properties are so good no additional zinc is needed.

 

Personally, with what you say about your car with a new engine, I would stick with the 10W-40 mineral oil as Carl says for a couple of thousand miles then change to synthetic in the same grade or perhaps a 5W-40.

Edited May 28, 2017 by Spinneyhill (see edit history)

[trimacar]

I've heard that one issue with synthetic oil in the much older engines is the higher flow rate of the synthetic oil leads to more (or increased) oil leaks.  Thus, a seal that may have worked with a thicker conventional oil may not hold back a high flow rate synthetic.

 

On my very old cars, I've gone to a semi-fluid grease, for example, as transmissions and rear ends are difficult to completely seal due to design.  This reduces leaks considerably.

 

I've never made the leap to synthetics, but know there are people (as mentioned above) who swear by them.

[Grimy]

Carl, those are wonderful stories, masterfully told.  Let's discuss when we meet, and also your Ecuador time.

 

I believe the important thing is that we each consider how our vintage iron is used, number of cold starts, how much long hot driving (as on Modoc Tour, for example), and make an informed choice.  Virtually any oil we can buy these days is VASTLY superior to what was available when these cars were knew.

 

Returning to Grant's question (we do go off on tangents around here), I'd probably continue with the 10W-40.  On my fleet with more experienced engines, I split the difference and run Shell Rotella-T 15W-40 diesel crossover oil--except for the very loose engine in the 1925 Pierce 80 sedan in which I ran 20W-50 because it was so well-worn and loose.  That engine is now being disassembled for a much-needed rebuild, but I did get 20K miles and 21 years out of an engine which was marginal when I acquired it.

 

I agree with Spinney on all his points except for synthetic, which I choose NOT to use in my cars.

 

And I agree with trimacar (David) on use of semi-fluid grease (=1200-1500 weight but good flowing) for early and necessarily-leaky (due to sealing technology) differentials and steering boxes.

[billorn]

I figure since I change my oil every year and dont drive more than about 2000-3000 miles that synthetic oil is too much and I wont get a benefit only a (much) higher cost. Grimy is right that any oil today is probably better than old oils so I buy a brand name 10W40 for my '56 Olds and 79 Chevy pickup. They dont complain and even tho I havent torn them down looking at the parts they still make good oil pressure hot or cold after all these years. They leak but I think all old cars should leak. If they dont then you know somethings wrong!!! Synthetic oil is definitely better but I dont think we dont use our old cars hard enough or often enough to get the benefits.

 

This comes up alot on other message boards I read and everyone usually agrees that whatever you use is better than what was available new and that if you have good oil pressure then dont worry too much about it. We dont use these old vehicles hard enough for it to matter right? When was the last time any of you powershifted an old car? Hit redline? Went more than 100 MPH? We drive these old cars like theyre made of glass so why worry about perfecting an oil mix in a car that will outlast us all?

 

Do any of you watch your diets as closely as you watch the oil you put into your old cars? LOL!

[Spinneyhill]

1 hour ago, billorn said:

Do any of you watch your diets as closely as you watch the oil you put into your old cars? LOL!

 

Never a truer word was written! Most of us know we shouldn't eat the rubbish we do...... coz our bellies are too big and we will suffer later.

 

Ref synthetics leaking, I read somewhere there was a time when one or two synthetic additive packages included something that softened (well, all right then, attacked) some types of "rubber". Seals and rubber impregnated gaskets might not have done well. But my reading also found that time had passed and they don't do that now... or the chemicals that do are masked with others to prevent the damage. Kind of like anti-corrosion agents in grease coz molybdenum disulphide is corrosive when the grease dries out.

[John_Mereness]

https://classiccarmotoroil.com/

[Grimy]

I place a lot more faith in someone who is NOT trying to sell me Something, especially overpriced Something.  Look at www.bobistheoilguy.com   Grant, if your car has roller tappets (as do 1931-35 Buicks and my 6-cyl Pierces), you definitely don't need enhanced levels of ZDDP that are beneficial mostly for 1950s-60s cars with strong valve springs. 

[Spinneyhill]

3 hours ago, Grimy said:

I place a lot more faith in someone who is NOT trying to sell me Something, especially overpriced Something.  Look at www.bobistheoilguy.com  

 

Agree. It is very hard to find independent advice on this stuff so you have to read around a fair bit.

 

Just a wee story. I was looking at anti-freeze + anti-corrosion solutions recently and the different technologies. There was and is a chemical used in some that attacks some kinds of seals. I asked the tech. rep. at Penrite, who market these chemicals, about it and I got an oblique answer that ignored the question about that chemical. Twice. They still use that chemical but say on the bottle it won't attack any gasket, seal, metal, plastic or any other material in an engine. My interpretation is they don't want to admit it can do that and they mask it with another chemical. So be very wary when asking for advice from someone with something to sell.