Oil recommendations
 

Hi all,
Getting ready to change oil for the first time.Don't know what's in it,but it's a 351W 400 h.p. Car is in Fla year round and driven on weekends.Also should mention,driven like a Cobra should be.Any advice on oil would be greatly appreciated.

Castrol 20W-50

Brad Penn is pretty good stuff as well.

I would never consider 15W or 20W oil in my Cobra engine. During a cold start, I want the oil to actually flow to where it's supposed to go.

I have been using a 5W-30 oil for years. No problems maintaining oil pressure lap after lap. And the bi-annual tear downs don't show significant bearing wear. So it's doing what it's supposed to do.

Heavier oil does not provide additional lubrication if you don't need. It just requires more energy and more strain on parts to move it around. You need a thick/heavy enough oil to maintain pressure in all situations. That's it; more is not better.

Last year I was reading that a slightly higher hot viscosity oil will provide better lifter stability at sustained high rpm's. I tried a 10W-40, but can't really see any difference. This year I went back to a 5W-30.

There are only two significant advantages to a synthetic oil - longer drain interval, and better heat resistance. If those two things are not important to you, use standard dino oil. Same results, less money.

A true synthetic oil starts with a PAO base stock, no dino oil. AFAIK, there are only 4 true synthetics on the market - and Mobile 1 is not one of them. The rest of the "synthetics" are really dino oils that have been refined enough to meet a marketing standard of "synthetic". The dino oils don't hold up as well in extreme environments, like racing and air cooled engines.

The diesel oils were somewhat better for a while. The gasoline oils reduced the ZDDP because it can damage the cats. Diesels didn't have cats, so they remained unchanged. For a while. Now some diesel angines have cats, so the ZDDP was reduced by about 25%. Not such a big deal any more. Now many diesel oils also have a certification for gasoline engines. That means there's very little difference from the gas oils for our engines. I think the big disadvantage to the diesel oils is their 15W or 20W rating.

IMO, you should choose a motor oil with the following criteria:
1. A dino oil or true synthetic according to what actually need- longevity or heat management.
2. Keep the W viscosity as low as possible.
3. Maximum viscosity high enough to maintain pressure in all situations, and no more
4. One that performs well in actual wear tests.

But, that's just my opinion. I could be wrong. :)

I second Bob's opinion. I am currently running 5W-30 Royal Purple and can maintain 25 psi at idle with the bearing clearances in my present engine. Normal pressure at cruise speed is 65 psi. Any higher oil viscosity would cause excessive oil pressure and strain on the oil pump and driveshaft.

John

A determining factor is the age and size of the engine block. I have a 1968 428 Cobra Jet in mine and I tried running 10-40 and it did not work so well, and was considering going to 10-30, but listened to a few people and went with the Valvoline 20-50 racing oil and the engine loves it. Oil pressure is only slightly higher than with the 10-40, but oil consumption is down and the engine runs smooth. I have solid lifters.

With a newer block or a small block, a lighter weight oil will probably be fine and I would follow Bob's advice. Unless you are running an older fe, or are racing hard, you probably do not need 20-50. Each engine is different and sometimes you have to experiment with different oils and viscosities and see what works best for your engine.

Good post Bobcowen---
I've used Gibbs, Brad Penn and AMSoil, all high quality IMO, all performed great. I don't worry about price at one change per year. A nice K&N filter and you will be good.

Thanks for all the input.Sounds to me SAE 30 is the oil for me.

Much, arguably too much, has been written about the need for ZDDP in motor oil for older engines - particularly those with flat tappets. I ran across an article (http://www.allpar.com/old/oils.php) that, while published in 2006, makes the case that newer oils (e.g. API grades SM & SN) are suitable for older engines as well, with the caveat that newly rebuilt engines probably need additives for the break-in period in order have the benefits provided by ZDDP.

Another option pointed out in the article is the use of motor oil designated API CJ-4, designed for diesel engines. I have read elsewhere that oil for diesel engines also has higher ZDDP than oil designated for gasoline engines - though that may no longer be true.

Interestingly, I found an old stash of Quaker State 5W30 and 10W30 in my garage labelled API SH, SJ - so that's the older stuff with higher levels of ZDDP. I guess it just sat there and gathered dust after I switched our daily drivers to synthetic, but I've got a use for it now.

Great post BobCowan, and I might add my engine ran about 5 degrees hotter when I went from 10w-30 to 15w-50. and gained about 6lbs pressure that I didn't need.
I do recommend a quality oil for the additive package. I tried and liked Brad Penn, Amsoil Z-Rod, Gibbs Hot Rod oil.
I have 35 lbs. at 1100 rpms Hot with 10w-30. The" Hot Rod/Classics Car/Z-rod" oils have claims to adhere to engine parts longer for a long storage. I pulled my pan a few times during the past several winters with these oils and found it to be true, but I haven't done any other testing or observations other than this.
I'll spend the money for one oil change a year, no reason not to.

didn't realize it was and old thread. sry for that, but I still like Bobs post :-)

I use 5W/30 or 5W/20 in my '90 model 302 block.

Dwight

It's HOT!!! in Alabama Dwight :D

yes I noticed

today it was over case and 80 degrees. I wore a jacket till late afternoon.

:) I love the sunny south

Dwight

Mobil 1 15w-50. Plenty of zinc/phosphorus and superior wear protection. And despite the conflicting opinions you might read here or elsewhere, it is a true 100% synthetic oil. The base stock argument has been throughly discredited by industry scientists, as well as the contributors, professional and otherwise, of the well known Bob the oil guy forum. The oil refining processes, and most importantly the properties of the finished product are what determines if the oil meets the definition and performance of synthetic oil. To be stuck on the base stock criteria of the oil to determine whether finished product can be called synthetic, or not, these days is a overly simplistic methodology that doesn't fit the issue, even partially.

I have been using it since 1997 in many vintage cars, mostly Ford powered. About 250,000 miles total with no lubrication issues or breakdowns. These engines were not babied. Numerous high speed endurance runs flat out in 4th gear for as long as a tank of gas would last.

Every engine that was torn down for inspection showed zero wear on all bearings.

Z

I just switched from Castrol 20w 50 to Castrol 10w 40. I did notice my cold PSI went from 60 to 55 and hot idle (850) went from 28 to 22. These are still good numbers so I see no reason to switch back in fact I may go to 0w 30 in the spring

I posted my engine specs on the bobistheoilguy forum. Mobil 1 - 0W40 was recommended by many.

I would disagree with you. How can it possibly be 100% synthetic if it comes from natural sources? That's like saying the banana on your counter is 100% synthetic because it meets the scientific description of a banana.

100% synthetic is just that - 100% manufactured and man made. Petroleum oil from dead dinos (or wherever it came from) clearly does not meet the definition.

Def: Synthetic: noting or pertaining to compounds formed through a chemical process by human agency, as opposed to those of natural origin

That's not to say that M1 is a bad oil. It's not. For the vast majority of cars on the road, it's a fine oil and will perform up to acceptable standards. But if you're paying synthetic prices for highly refined dyno oil, you're getting ripped off (IMO).

A true synthetic will perform better in difficult situations, like air cooled engines, and I have the UOA's to prove it.

BTW, where did you get bearings that never wear out? I'd sure like to put some in my engines. :)

disagreement is fine. It would be a boring world if we all marched in step.

However, the debate has moved on (some time ago) as to what meets the industry standard of a synthetic oil. It's not that vital to the definition of synthetic what you start with. It's far more important what you end up with when the refining process is over. Critical are the size and shape of the oil molecules. Relatively recent developments (last 15 years) in the petroleum sciences now make it possible to achieve uniformity in molecule size and behaviors without adhering to outmoded models of refining.

But of course you will still see boutique oils that like to tout their base stocks as being the only "true" synthetic. Good marketing, but not current science.

As for bearings that "never wear out". I wish I had some too. what i've experienced are bearings that show zero measurable wear in the time and milage frame mentioned. Quite different from "never". That's fine, I don't expect to last forever either.

Z.

This is a very interesting article that blows holes in many myths and misunderstandings about motor oil - particularly with regard to viscosity and the debate between dino and synthetic lubricants. Well worth reading: Motor Oil 101 - Bob is the Oil Guy - Bob is the Oil Guy

After reading this I'm thinking switching from 20W50 dino to 5W30 or 5W40 synthetic, depending upon running oil pressure in a hot engine. Hint, hint...

Another convert to logic, reasoning, and knowledge. Congratulations, and welcome to the enlightenment. :MECOOL: