5w-20 in Older Engine? Ford 7.5L V8

[The_Eric]

Originally Posted By: Garak
My beef in this discussion is that I don't see the benefit. The fuel economy savings wouldn't outweigh the risk in my mind. While the manual allowed for a 5w-20, we also have to remember that recommendation disappeared in subsequent years, then reappeared.

It's probably not going to hurt a thing, but there are other ways to save fuel.


It's my opinion that at this point, the risk is only perceived. We really have no hard data to go on. We do know that rod and main bearing clearances are in the ball park of each other. The 460 coming in at .0015" to .002" on the mains (some sources say .0015" max) and a 4.6 is .00098 to .0017". Not a huge difference. I'm sure the rods on a 460 are looser, but enough to mandate a 30 grade? Bet not.

Originally Posted By: OVERKILL
Originally Posted By: The_Eric

Also, can you tell me what separates a thick 20 from a thin 30? Or what's the difference between a cool 20 and a hot 30? Bet you'd be hard pressed to tell. Ford allowed the use of a 20 grade oil in the wintertime and did not make the distinction of miles driven. They knew the oil would be plenty cool and therefore still provide proper lubrication.


HTHS.


This true, and a good point. I think that with bearing clearances being what they are and a relatively gentle highway cruise with low ambient air temps (and likely low oil temps), the additional HT/HS is not required.

 

[OVERKILL]

Originally Posted By: The_Eric
Originally Posted By: Garak
My beef in this discussion is that I don't see the benefit. The fuel economy savings wouldn't outweigh the risk in my mind. While the manual allowed for a 5w-20, we also have to remember that recommendation disappeared in subsequent years, then reappeared.

It's probably not going to hurt a thing, but there are other ways to save fuel.


It's my opinion that at this point, the risk is only perceived. We really have no hard data to go on. We do know that rod and main bearing clearances are in the ball park of each other. The 460 coming in at .0015" to .002" on the mains (some sources say .0015" max) and a 4.6 is .00098 to .0017". Not a huge difference. I'm sure the rods on a 460 are looser, but enough to mandate a 30 grade? Bet not.

Originally Posted By: OVERKILL
Originally Posted By: The_Eric

Also, can you tell me what separates a thick 20 from a thin 30? Or what's the difference between a cool 20 and a hot 30? Bet you'd be hard pressed to tell. Ford allowed the use of a 20 grade oil in the wintertime and did not make the distinction of miles driven. They knew the oil would be plenty cool and therefore still provide proper lubrication.


HTHS.


This true, and a good point. I think that with bearing clearances being what they are and a relatively gentle highway cruise with low ambient air temps (and likely low oil temps), the additional HT/HS is not required.


Note that the 4.6L has 6-bolt mains, a skirted block and a gyrator crank-driven oil pump of much higher volume and pressure. The Modulars were engineered to have a completely rigid bottom-end which allows them to thrive on thinner oils. I can't say I'd have the same faith in an old 385 engine being as tolerant.

 

[OVERKILL]

Bottom-end of a 460:

Bottom-end of a 4.6L: (and correction to my earlier post, they aren't all 6-bolt mains, this one is 2-bolt + the lags, making it 4-bolt)

You can see the deep skirt though.

Here's the 6-bolt variant:

 

[The_Eric]

Originally Posted By: OVERKILL
Note that the 4.6L has 6-bolt mains, a skirted block and a gyrator crank-driven oil pump of much higher volume and pressure. The Modulars were engineered to have a completely rigid bottom-end which allows them to thrive on thinner oils. I can't say I'd have the same faith in an old 385 engine being as tolerant.


I can't speak to the volume, but after looking though Jim Allen's thread in the oil filter section, I'm inclined to believe that a mod doesn't have that much more pressure than an old 385.

Of course at this point it's mostly guessing (since we know nothing of th op's oil pressure or pump output), but I wonder how much more volume a mod puts out if the pressure is a bit more, but with a bit less bearing clearance? Wouldn't the volume be a function of pressure and bearing clearance?

 

[OVERKILL]

Originally Posted By: The_Eric
Originally Posted By: OVERKILL
Note that the 4.6L has 6-bolt mains, a skirted block and a gyrator crank-driven oil pump of much higher volume and pressure. The Modulars were engineered to have a completely rigid bottom-end which allows them to thrive on thinner oils. I can't say I'd have the same faith in an old 385 engine being as tolerant.


I can't speak to the volume, but after looking though Jim Allen's thread in the oil filter section, I'm inclined to believe that a mod doesn't have that much more pressure than an old 385.

Of course at this point it's mostly guessing (since we know nothing of th op's oil pressure or pump output), but I wonder how much more volume a mod puts out if the pressure is a bit more, but with a bit less bearing clearance? Wouldn't the volume be a function of pressure and bearing clearance?


Not with a positive displacement oil pump sir

It moves the same volume of oil regardless, assuming the relief is closed.

And with Jim's setup we were seeing 80+psi with 180 degree coolant temps on the 10w-30:

You aren't seeing that on a 460. It, like the Windsor, probably tops out on the relief at about 65psi.

And even with the 5w-20, Jim was seeing 75psi at 180 degrees:

 

[Garak]

Originally Posted By: Shannow
The University 101 has one thing right, and that cars have thermostats...so when the vehicle is tooling down the highway, the engine is at temperature (thermostat design aside), regardless of ambient.

Anecdotally, at least, there is a minor difference between oil sump temperatures in ridiculously cold temperatures and normal summer temperatures. That I simply know from the thermometer in my hand when I dump oil on it during a change; that was pretty clear in the taxi years. Summer had uncomfortably warm oil, winter oil at temperatures wasn't so uncomfortable.

As for ambient, we didn't switch grades by season. It was 10w-30 all year, since there were no cold starts. A monograde probably would have done just as well. The ambient thing, in my view, matters most at very cold starts (i.e. MRV ranges) and perhaps at high temperatures with some really hard use.

Originally Posted By: Shannow
I'd be happy with a 20 in said engine if I was planning to and from work, not so on a long highway, and not towing, regardless of the range in the manual, and the outside temperature.

I don't know who you are, but Shannow would likely not approve of you using his computer and BITOG account.

Seriously, yep, if it were short trips, I wouldn't care. But, I do have some well grounded fears about fuel dilution from Ford of around that vintage. A 30 grade (at under halfway through a short OCI) would cause the oil pressure light to go on and hot idle. And my trips tended to be around 100 miles each time. That was the reason I stuck to MaxLife 5w-30 in the winter and a 15w-40 in the summer. That kept the warning lights off (and the leaks to something less than a river).

@Miller88: There were multigrade 20 references (and products, though rare) at the time. Mobil, I believe, had the product out there even earlier, as Mobil 1. If tig1 reads this, he'll let us know since he used it at the time.

 

[Garak]

Originally Posted By: The_Eric
It's my opinion that at this point, the risk is only perceived.

That's certainly possible, but bottom end rigidity is important, too. Heck, I was using thin for a long time, as did my father. Between fleet and farm usage, the only time he ever touched a 40 grade was for diesels, and he used 20 grades as soon as Ford/Lincoln/Mercury called for them.

 

[The_Eric]

Originally Posted By: OVERKILL

Not with a positive displacement oil pump sir

It moves the same volume of oil regardless, assuming the relief is closed.

You aren't seeing that on a 460. It, like the Windsor, probably tops out on the relief at about 65psi.


Ah yes. I always get that turned around. So indicated pressure is more a function of the (fixed) volume and bearing clearance.

 

[SwampSurvivor]

Originally Posted By: Garak


@Miller88: There were multigrade 20 references (and products, though rare) at the time. Mobil, I believe, had the product out there even earlier, as Mobil 1. If tig1 reads this, he'll let us know since he used it at the time.


Strange. For some reason I thought 5w-20 was a 90s thing.

 

[Shannow]

Originally Posted By: The_Eric
We do know that rod and main bearing clearances are in the ball park of each other. The 460 coming in at .0015" to .002" on the mains (some sources say .0015" max) and a 4.6 is .00098 to .0017". Not a huge difference.


I wonder if my boss will give me a similarly small pay increase if I put it in those terms...

 

[Garak]

Well, it was a bit of a 1990s thing, but I guess it was also around earlier, albeit much rarer.

 

[Shannow]

Originally Posted By: The_Eric
Originally Posted By: OVERKILL

Not with a positive displacement oil pump sir

It moves the same volume of oil regardless, assuming the relief is closed.

You aren't seeing that on a 460. It, like the Windsor, probably tops out on the relief at about 65psi.


Ah yes. I always get that turned around. So indicated pressure is more a function of the (fixed) volume and bearing clearance.


If you have a standpipe of oil feeding the low pressure area of a single bearing, the bearing will "refill" with enough oil to replace that which is forced out axially along the bearing in the high pressure areas...it will swallow the oil that it needs.

The oil pump replaces the stand-pipe, and the pressure is built as the bearing doesn't need all the volume that's there...pressure equilibrium is reached when enough extra oil is jammed out the low pressure, non loaded side, and not running through the bearing.

It increases the bearing's operational visocity some by dropping the bearing average oil temperature a tad...wastes power, by pumps just "pumping" through an orifice.

 

[92saturnsl2]

An update for anyone interested.. I've put just less than 1200 miles on since changing the oil and the engine hasn't blown itself to bits, no strange noises or anything of the sort.

The only negative I've observed so far is a pretty noticeable increase in oil consumption, which I suspect is leaking from the rear main. I replaced all gaskets I could reasonably get to over the summer, but obviously the rear main stayed until such time as it gets bad enough to warrant pulling the engine. It's next to impossible to do while in the truck. I've added about 3/4 of a quart so far.

This latest cold snap is the proof I needed of the merit in using a thinner oil in the winter months. In single digit temps, it was 6-7 seconds of labored cranking before it would fire up. It's not fuel injected after all so relies on air moving through the carb to draw fuel-- getting it to crank faster helps immensely.

Well the last couple nights it got down to about -11, and starting it was pretty much effortless. Couple pumps of the pedal, turn the key and bam. HUGE difference compared to 15w-40.

I haven't noticed the oil pressure gauge dropping any, it stays right up near high like it used to, but I suspect the extreme cold is keeping the oil from getting very thin. One thing to note is that the oil cooler on this engine is oil to air (not oil to coolant like modern engines), so its temperature is largely unregulated and dependent on ambient temps. I suspect this is why Ford specifies such a wide range of viscosities, all based on expected temperature.

I've only logged fuel economy under 10mpg once since the switch to 5w-20, but the average is about 10.25. This is a noticeable improvement, especially considering that colder weather usually has a negative effect on fuel economy, plus the 5 minute warm-up in the morning.

I used to subscribe to the thicker is better train of thought, but my own UOA on the last couple vehicles I've owned have shown negligible or negative gains in wear metals, and nearly always worse fuel economy (a trival amount, but worse nonetheless) with the thicker oils. I'll gladly trade a little oil consumption for a healthy sounding engine on a cold start, arguably less wear in cold weather (we'll let the future UOA do that talking, however) and a few extra pennies saved in fuel. I think mine's the only rig in the parking lot at work whose valvetrain isn't clattering for 15 seconds when started at 0 degrees

That must be saying something.

 

[OVERKILL]

Originally Posted By: 92saturnsl2

I used to subscribe to the thicker is better train of thought, but my own UOA on the last couple vehicles I've owned have shown negligible or negative gains in wear metals, and nearly always worse fuel economy (a trival amount, but worse nonetheless) with the thicker oils. I'll gladly trade a little oil consumption for a healthy sounding engine on a cold start, arguably less wear in cold weather (we'll let the future UOA do that talking, however) and a few extra pennies saved in fuel. I think mine's the only rig in the parking lot at work whose valves aren't clattering for 15 seconds when started at 0 degrees

That must be saying something.


A UOA doesn't tell how how an engine is wearing. And they are particularly useless in comparing wear between oils. For that you need to do tear-downs, which you obviously aren't going to do so it doesn't really matter.

Will they tell you of an impending mechanical failure? Possibly.
Will they tell you of a possible air intake tract leak? Yes.
Will they help you determine how long you can safely run a particular lubricant? Yes
Will they tell you about fuel dilution? Yes
Will they tell you about a coolant leak? Yes

But their purpose is not to allow you to contrast "wear" between different lubricants and never has been.

 

[92saturnsl2]

Originally Posted By: OVERKILL
But their purpose is not to allow you to contrast "wear" between different lubricants and never has been.


You're taking my statement / words down a path I never intended it to be taken. I'm not suggesting that a UOA is the end all determination of good oil versus bad.

However a UOA *does* quantify wear metals to a point. A large increase in wear metals (compared to baseline) points to a problem. The fact that I've not seen said large increase with thinner oils tells me all I need to know. It's not telling me that a thin oil is better, or vice versa. I never made that statement. I simply stated that I used to believe that thinner oil would be harmful or somehow worse-- and I've seen nothing so far to substantiate that.

Obviously a teardown of an engine would be a good indicator of excessive wear, but even that is hardly quantifiable unless you have an exact copy, driven under exact same conditions to compare it to.

Edit: I did make the comment that a future UOA might confirm the notion that the thinner oil protects or wears better in cold-- and indeed you're right, a UOA will be largely useless in that regard, unless something very obvious pops up. But it's doubtful a small change in oil viscosity would cause that.

 

[OVERKILL]

Note that I'm not saying that the 5w-20 is necessarily going to cause you issues. My point is simply that if it does create different wear characteristics in your engine, it is quite likely that you aren't going to see those in a UOA. This is due to the very narrow range of particle sizes they sample.

Glad to see we agree on the last point

Note that I'm not trying to discourage you from doing UOA's, I do them myself! I simply try and keep some perspective on their value.

 

[JR]

Run the 5w-20, nothing wrong with light oil. heck ford says it in the manual.

ken

 

[Garak]

Originally Posted By: 92saturnsl2
However a UOA *does* quantify wear metals to a point. A large increase in wear metals (compared to baseline) points to a problem.

That works, really, only when you're using the same oil and viscosity all along as the baseline.

 

[dareo]

i just feel bad that you gotta gas for a carb'd 7.5L; 120 miles a day no less. Not much gets worse MPG than that. At only 225 rated horsepower in such a massive engine you could probably run it on Redline 5 weight if you had to. I wouldn't worry about 5w20.

 

[92saturnsl2]

Yes the situation sucks, but it was worse than the alternative. I've been putting 30k miles a year on a used '09 Caliber SRT4, accumulated 130k (not all mine), which needless to say hurts the resale value. I had a buddy offer to buy it for what I owed (about 10K), so I couldn't refuse.

So the truck gets put into daily driver service-- I knew it would cost close to $200 a week for my commute, but I can handle that for the short term, until I but a new car in February.