Thin and thick.....

[Bambam]

I realize what open forums are all about but you guys are like 5 year olds trying to get to be first in line! Don't listen to Mr X he doesn't know, Mr Y, he's way off, I think blah,blah,blah. Unless there is hard data behind what you recommend, why should we believe you?

.

 

[dwendt44]

Quote:
I've never seen anything in his writing about the hydrodynamic wedge of oil that builds up in rotating journal bearings which is the real reason the oil holds the parts apart.



He does mention pressurized oil between metal parts.
As many auto mfgs are going his way, albeit slowly, he may be onto something.

 

[mechtech2]

Originally Posted By: CATERHAM
Originally Posted By: mechtech2
I still am not sure of what 'pops the valve' is supposed to mean.

It's the pressure release valve that's on all oil pumps.
It's activated if you rev' an engine too high with cold (thick) oil and at operating temp's if you're running an oil much thicker than necessary.


Some pressure relief valves are not on the oil pump itself , but in the circuit elsewhere, like in the block or cover.

 

[CATERHAM]

Originally Posted By: ac_tc
Ok.
Pops the valve- open bypass valve on oilpump.
Still a 40 hdeo gives me with warm engine and oil (90/110 degC)
an oilpressure (slightly below 3 bar) thats on the edge of popping my bypass
at my typical running speeds.
Of course it wouldnt be great at higher engine speeds
but the question was if that wouldnt be optimal
for my use. Note that the engines runs "semi lugged" almost all
the time (cruises at 1500-1700 and sometimes during climbs 2400)
If i follow dr H´s rec ill use an oil that gives pop off att 4600
and thats extremely seldom my engine is at that speed.

By the way it costs about 1400 skr or 225$ to fill it with gas
and the oil i use costs 7$/ liter but a liter of mobil 1 5-40
nets around 22$.....(i use around 40-60 liters a year, so i dont mind getting it in 20 liter cans)

It's good that you're not running in by-pass mode most of the time but the fact that you can't use maximum rev's even when your oil is fully hot is a sure fire indicator that you're running an oil thicker than optimum.
What is the OP spec' for your engine? If I'm not mistaken it's something like 50 psi (3.5 bar) at 3,000 rpm. Any oil that generates OP higher than that is thicker than necessary. As mentioned before the spec' oil for both your vehicles is a 5w30 I believe, so there is no benefit to running a 40wt oil and you have confirmed that with your OP readings.

 

[Jim Allen]

If you don't know when the bypass opens via factory info, how can you tell when it opens?

I got some data on my truck but haven't taken the time to noodle anything out.

RIght now: With the oil at 50F, oil pressure peaks at 88 psi @ 4500 rpm. Stays there past that but I didn't check past 5000. With the oil temp at 195F, it will max out at 76 psi at about 4500.

I can't get Ford specs for the 5.4L engine but Melling makes an OEM replacement. Using a standardized test oil (equivalent to 10W30), their pump delivers 38 psi @ 200F at 800 rpm and the bypass begins to open @ 69 psi @ 200F @ 2000 rpm. The pump is a Gerotor type, driven off the crankshaft snout.

Interestingly, Ford lists 75 psi @ 2000 rpm with a "warmed up" engine as "normal" oil pressure but does not directly specify the oil.

AERA lists 40-60 psi @ 2000 w/ "warmed up engine" as normal.

 

[CATERHAM]

Jim, in any vehicle that I have had experience, the by-pass level is the point at which the cold oil pressure no longer continues to rise with increased rev's; this assumes the OP gauge is not pegged like it is in my Porsche.
When the oil is hot the OP will no longer reach the by-pass level at maximum rev's with the spec' oil.

 

[dakota99]

I have a 99 Dakota with the 5.2L engine, and i use PP 5w30 with no issues year round. On cold startup the pressure gauge just goes all the way to the right, im assuming to the point of bypass. Hot idle is around 35 psi, hot cruising (60 mph, 1700 rpm) yields somewhere in the range of 50-60 psi. I've towed some pretty heavy loads with the PP and it's performed perfectly. I would think 10w40 would be unnecessary. iirc curb idle pressure for these engines is like 8 psi or around there.

These readings are from the stock gauge if that means anything.

 

[Steve S]

Originally Posted By: aquariuscsm
Isn`t the golden rule to use the "thinnest" grade possible to give you the best protection? For example,if your car specs 5W30-20W50,wouldn`t 5W30 be the best,with 5W20 being too thin,and 10W30 being unnecessary?
It depends on the operating conditions and temps.

 

[jorton]

Originally Posted By: ac_tc

What if my engine pops the valve at 1700 rpms and almost all
the time runs at that speed mostly towing, is then the reasoning ok?


Yo motor is already seized.

 

[ac_tc]

I actually doesent know that it pops at 1700..
But im pretty sure it does since it doesent build any more
pressure above that (just a slight increase with rising speeds)

There a difference between cant use maximum revs and dont use.

 

[CATERHAM]

Originally Posted By: dakota99
I have a 99 Dakota with the 5.2L engine, and i use PP 5w30 with no issues year round. On cold startup the pressure gauge just goes all the way to the right, im assuming to the point of bypass. Hot idle is around 35 psi, hot cruising (60 mph, 1700 rpm) yields somewhere in the range of 50-60 psi. I've towed some pretty heavy loads with the PP and it's performed perfectly. I would think 10w40 would be unnecessary. iirc curb idle pressure for these engines is like 8 psi or around there.
That sounds about typical for a light 5w30 like PP and since you're well above the min' OP spec's you could likely run a 20wt oil if you liked without testing them.
Doesn't Dodge spec' a 5W-20 for the past couple of years now?


These readings are from the stock gauge if that means anything.

 

[CATERHAM]

That sounds about typical for a light 5w30 like PP and sinceyou're well above the min' OP spec's you could likely run a 20wt oil if you liked without testing them.
Doesn't Dodge spec' a 5W-20 for the past couple of years now?