Engine oil viscosity vs oil pressure Options

[Geezer914]

2056 engine with 2000 miles running Driven 15w50 oil. Start up pressure is 78lbs. at 75 degrees. Oil pressure when hot is 40lbs. at 3000rpm. If I switched to 10w40 would my start up pressure be less along with my hot oil pressure?

[emerygt350]

I don't think you will see a start up difference since that is probably getting bypassed to the sump by the oil pressure control valve. At hot, if you are using a quality synthetic oil, I suspect you will see a small change depending on your oil pump.

I just installed Tangerine racings oil control valve (the front one that directs traffic to the oil cooler). It will be interesting to see what that does when I finish my 2056 build.

I am also a fan of thinner oils, I think it is a good compromise between oil pressure and flow volume in an oil cooled engine. I use 0w40 (mobil 1 euro). I have a little higher pressure hot at 3k than you but I also just found out I have a mellings oil pump so that might be it.

[brant]

Make certain the 0-40 has zinc in it
I think it’s made for modern cars with emissions
And may not be heavy in zinc…. But haven’t verified

You’ll loose your cam and lifters in short order without zinc

[914werke]

(IMG:style_emoticons/default/agree.gif) I think this is one reason folks default to using 20/50 in that Mobile1 is the only ZINC formulated product readily available at most FLAPS.
In the PNW we rarely get to the temps that might require using such heavy oil..
I try to keep "Penngrade 1" 10/40 in stock (IMG:style_emoticons/default/smile.gif)

[mlindner]

Geezer, just stick with the Driven 15/50. Its the best. I'm done with 10/40 Mobil for these old air cooled engines. Best, Mark

[emerygt350]

Euro mobil 1 has decent zinc levels. Remember these engines started with 30 weight. 50 weight is just to thick in my opinion (he we all have one). Think about the pressure necessary to blow a cup of thin syrup through a straw and how quickly that syrup will be moving, vs a cup of water. More flow, less linger time, although you don't want it to not linger long enough. You want the oil to take some heat, create a protective barrier, and then get out of there.

I have a higher (not super high) performance flat tappet cam in the mustang and it has done perfectly fine with mobil 1 euro 0w40 for 20,000 miles. No flat lobes, runs great, so great I demolished my spider gears in the rear diff during my last autocross.

A little zinc is good, a bunch of zinc doesn't seem to improve anything. I think the sweat spot is supposed to be around 1000ppm. or whatever unit they use. The only time it even matters is at start up and at start up you want light thin oil so it gets everywhere quick and in volume. Having your engine have to push sludge at start up is probably way worse for it than having thin oil when it is hot.

[brant]

I think the sweet spot would is actually 1200-1400 ppm
You’ll find out the hard way on your rebuilt
I’ve seen a lifter worn through with an actual hole in the face from the wrong oil
Especially new parts that aren’t coated previously


Owner’s decision
Most pro builders will tell you
Hard lesson to learn

[emerygt350]

I think the sweet spot would is actually 1200-1400 ppm
You’ll find out the hard way on your rebuilt
I’ve seen a lifter worn through with an actual hole in the face from the wrong oil
Especially new parts that aren’t coated previously


Owner’s decision
Most pro builders will tell you
Hard lesson to learn

A pro builders anecdotes are only worth as much as they agree with other pro builders anecdotes. And that is why there are soooo many different views on how to keep a flat tappet happy. The one agreement is that it is only at start up. The metal conditioning that the zinc provides appears to be real but it is really just for that short moment when the engine may be oil starved. The last paper I read, if I remember right, saw disadvantages for running up to that 1400 level. For the life of me, I can't remember what it was, maybe it changed another characteristic of the oil.

I am not going to be one of those guys that says it does nothing, I think it does, but it really does just the one thing and that thing under one circumstance (low oil barrier start up). I do think the crap cams that were being sold back when zinc was being removed also lended itself to this zinc craze. "look, as soon as I started using zinc the cams were fine" lined up nicely when cam quality improved in the 2000s.

I will dig around and see if I can't find that paper that talked about zinc conditioning.

Here is one of the papers but I need to go into the office to get the hard copy.
https://link.springer.com/article/10.1023/A:1019191019134

There was another paper that looked at levels in particular.

There is some interesting stuff in here under applicataions.
https://books.google.com/books?hl=en&lr...oil&f=false

[brant]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

[emerygt350]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

[Geezer914]

What are you getting for hot oil pressure using 10w40 or 0w40?

[Superhawk996]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

Oil preference is a religion (IMG:style_emoticons/default/aktion035.gif)

[r_towle]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

So then, fact matter.
Results matter.

Much of the advice here is factual, based upon bad experiences (IMG:style_emoticons/default/smile.gif)

[930cabman]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

Oil preference is a religion (IMG:style_emoticons/default/aktion035.gif)

I am an island (IMG:style_emoticons/default/shades.gif)

[emerygt350]

I get 40 at 3k but there is so much more going on there.

Until I see some replicated controlled experiments on the impact of zddp on flat tappets, I will take all builders anecdotes as exactly that.

[emerygt350]

Here is my 302 running 0w40 at 2k rpm doing 60mph on the way to autocross this morning. Obviously no comparison, the engines tolerances were built for 40 weight but at 20k on the rebuild its cam is not flat. But that is only an n of 1.

I remember back to the old opel 1.9s from the late 60s and 70s, their cams would go flat regardless of the oil you put in it. I think it was a 'feature'.

[brant]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

So where is your data?
That your mustang is ok?
Anything else?

The race shop/machinist I’ve worked with for 30 years has built hundreds of air cooled motors both -4 and -6.

And has run hundreds of oil analyses

Pretty sure raby has also run hundreds of oil analysts
To come to his conclusions also

What data are you using?
It seems your gut and the mustang?

Air cooled motors are inherently flawed in the cooling department
And have increased requirements for cooling/oiling

[Superhawk996]

OP asks question about oil pressure

Turns into full on debate about ZDDP, how much is enough, and analogies about need for it. (IMG:style_emoticons/default/av-943.gif)

Guys, let’s face it, there is a lot of published data that shows the benefits of ZDDP as an anti-wear agent. Beyond that, I have never found an exhaustive study of exactly how much ZDDP is optimal for any flat tappet cam, less yet flat tappet cams in air cooled engines. I doubt a large sample, statistical, dyno and real world mileage study exits anywhere. When it comes down to arguing about 900 parts per MILLION or 1300 parts per MILLION, it has become a pointless discussion.

The engine builders don’t have statistically relevant data and high mileage real world wear studies.

The OEM’s aren’t doing the statistically relevant dyno testing on our antique engines. The oils they dyno tested with back in the day are no longer available.

The oil companies aren’t doing backward compatibility studies on antique air cooled engines.

So there you have it. The only agreement is: ZDDP good - getcha’ some.

Beyond that - you’re on your own. Trust which ever oil preacher you want, but it’s still a religion.

[r_towle]

I recall Jake did a bunch of testing which may have been published back in the day along with Brad Penn oil.

[r_towle]

Just saying
I saw the lifter in 2010 that wore a hole in the face from the wrong oil oil. No kidding

You’ll see
Pros know what they talk about from experience
At least my mechanic / machinist has that experience after 40 years

Yeah, but I am a scientist.

Oil preference is a religion (IMG:style_emoticons/default/aktion035.gif)

I am an island (IMG:style_emoticons/default/shades.gif)

Beach pictures or it’s not real.