Oil pressure with 10w30 vs. 15w40?

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I am using Chevron Delvac 15w40 in 7.5L
and the oil pressure isn't that good,
it's at about 1/4.

It burns lots of oil of every kind.

would it get better pressure with 10w30?
 
I would think the 10w30 would give you lower pressure due to it being thinner at running temp.
You would have to get thicker to possibly raise the pressure, but remember it's only masking the real problem. I would fine out what the problem is before going to thick.
cheers.gif
 
Normally pressure will be higher with 40 wt vs 30 wt. In my F150 in summer weather, 30 wt gave me around 36 psi whereas 40 wt gave me about 42.

Do you have a good oil pressure gauge? A lot of later model Fords (and not so late model like my '92) came with dummy oil pressure gauges that are either on or off and the needle just sits there looking good but means no more than an idiot light.
 
pacem, both of the above posts are correct. If you are worried about a oil pressure problem....it is best to install a decent oil pressure guage.

40wt oil cSt starts out in the range that 30 wt. tops out. Oil pressure is not everything it's cracked up to be. First see if you are in the general guidelines of the OEM specs with a good guage.

If you do have a minor problem, you could start a cleaning of the engine. If you have a major problem...I would R&R the oil pump.
 
Oil pressure is meaningless, as long as there is at least some pressure (thus flow). Obviously a less viscous oil will generate less pressure, but more flow.

Don't worry too much about it. Higher oil pressure is actually bad since an engine has to work harger (and run hotter) to maintain it.

Actual (accurate-reading) gauges were removed from most vehicles a long time ago because rednecks and morons were, among other things, installing improper grades of oil just to get a higher reading on the pressure gauge.
 
"Oil pressure is meaningless" Not at all, just meaningful in more than one way. Increased flow due to worn clearances causes a drop in oil pressure...that is not meaningless. Lower oil pressure due to a blocked pickup screen is not meaningless. Higher oil pressure due to bits of filter material in the passages is not meaningless.

So...very meaningful, but not as a standalone item.


Ken
 
thank you for shedding some light on it...

It's well within the range. I didn't realize it was a glorified idiot light.
 
Oil pressure is no more over rated then oil flow is. One positive thing about oil pressure is that oil pressure can be easily measured. No of these so called oil flow nuts have any idea how much volume of oil each part in their engine is receiveing at any given RPM. These same people have no means of dynamicly measureing flow either! Engine manufactures have strugled for years to try to determine volume of oil each parts needs at any given RPM and load and how much they are actualy getting. THeir is a reason that oil pressure is the gold standard for diagnostic purposes!

Most people also fail to take into account how much of an increase in flow at any given pressure it would take to make a difference. This is especialy true when you look at cold temp. versus high temps. For example if a 5W30 is safe to use at -25°F in an application then how is a 15W40 hurting anything at 80°F in that same application? Flow is meaningless with out pressure and pressure is not of much use if flow is restricted!
 
quote:

Originally posted by JohnBrowning:
Oil pressure is no more over rated then oil flow is. One positive thing about oil pressure

But its fairly safe to assume that all other things being equal, a lighter oil will increase flow per unit pressure applied by the oil pump.

A constant displacement pump will merely require more shaft work to move a thicker oil. A constant pressure pump will move more 'thinner' oil at the same pressure as less 'thick' oil is moved.

quote:


is that oil pressure can be easily measured. No of these so called oil flow nuts have any idea how much volume of oil each part in their engine is receiveing at any given RPM. These same



Its fairly safe to assume that a thinner oil will give you at least an equivilant volume of oil (with lower pumping losses), or higher volume of oil (with similar pumping losses).

If the oil is capable of doing its functions without thermal decomposition, then its obviously suitable. In the past, thin oils didn't have the volatility, flashpoint, and oxidative resistance required, hence the 'thicker is better' wisdom was born.

quote:


people have no means of dynamicly measureing flow either! Engine manufactures have strugled for years to try to determine volume of oil each parts needs at any given RPM and load and how much they are actualy getting. THeir is a reason that oil pressure is the gold standard for diagnostic purposes!



Sure, but its like UOA's. You can't compare a UOA from a Saab engine against a UOA from a Ford engine, and draw a conclusion about the quality or efficacy of a particular oil.

An engine will have a spec for a certain level of pressure running the manufacturer-specified lubricant. Thats a benchmark diagnostic value only -- not really useful for determining flow adequacy with a different viscosity of oil.

quote:


Mtemp. versus high temps. For example if a 5W30 is safe to use at -25°F in an application then how is a 15W40 hurting anything at 80°F in that same application? Flow is meaningless with out pressure and pressure is not of much use if flow is restricted!


1) An engine won't run at an oil temperature for very long at -25degF. Maybe a minute or two at the most, on a -40degF day in the Arctic until the oil experiences some heating.

2) Its impossible to induce flow without pressure. That's just Newton's law of physics (F=ma), or whatever they call it in fluid mechanics.

3) The wisdom to use a thicker oil in an engine with a worn out oil pump (just to bring up pressure) may very well be flawed as well. An engine with a worn out pump, or worn out bearings, may very well be suffering from poor flow. Moving to a higher viscosity is actually counterproductive. Though I do admit, thicker oils probably have benefits in terms of ring seal, and can withstand sludge-induced hot-spots much more easily than thin oils. Not to mention the issue of leaks and oil control in components such as valve stem seals.
 
But if you go too thin (and we probably are talking thinner than 5w20 here) and most of the oil leaks out the main bearings and big ends, then the top end could be starved, even though you have very high flow.

If the manufacturer says you should have 40 to 60 psi at 2000 hot and you only get 30, should you go to 40 weight to get within the specified range?

I heard Ford went to the dummy oil pressure gauge because they got tired of people complaining that there was something wrong with the engine because the gauge fluctuated a lot, but probably it was a cost saving measure.

Hey, I notice the voltage gauges in my Fords actually seem to be real, but that Ford forgot to include the numbers so you could tell what the voltage is. All they put was 8 at the bottom and 18 at the top. If you look at the normal range, it appears any voltage from 9 to 17 is normal--not true. Try it. With key on and engine off it should give batery voltage and be slightly below center (about 12.5 volts), with engine running it should give alternator output (about 14.4), then turn on the blower fan all the way and watch it dip (goes to about 13.9 on my digital voltage gauge, but just a slight movement on the Ford gauge).
 
Ford got rid of the pressure sender in 1987 for most US models. They put in a pressure switch and 20 ohm resistor (to make the needle sit at half instead of full scale). Why they left the gauge in there and didnt just put in a light is a total mystery as far as cost goes.

To answer the original post, if there is considerable oil usage and no external leakage with 15W-40, the engine probably needs intake valve seals.
 
pitzel, not so. A thinner oil only helps if the pumps clearances are such that it can take advantage of the reduced drag that the zinner oil represents. All positive displacement geared oil pumps hemorage oil. Their is is a point that the amount of oil hemorageing past the pump's gears off sets the the advantages of a zinner oil. You also have to take into account that multiviscosity oil are not newtonian at all. Multi-viscosity oil are compressable.

Another factor about reduced drag is again that reduction in drag also works against you at some point. The thinner oil will be squeezed out from between spaces much easier and much faster then a thicker oil. this means that it is not going to hang around as long between the parts you are trying to keep seperated when a load is applied. So by effect you have to have a greater volume of the thinner oil to account for this! This is why thickners are added to oil to make a grease for some applications. The thickners do nothing to reduce friction or wear directly they are their to keep the oil in place so that the additives and the oil can do their job.

So you are decieveing yourself if you think flow is going to save you more then HTHS and additive chemistry in all but cold winter starting situations. My UOA's for my 2003 Camry look better with a 0W40 with a great after market oil additive then M1R 0W30+ LC. Both were dureing the winter and both were in at least 6 months. The better looking UOA had 3 times the milage and 7 months on it. How much flow difference do you think their is between M1R 0W30 and M1 0W40? THeir is however a difference in HTHS and the additive chemistry.

The resaon why companys have been working so hard to determine flow needs to various parts and total flow needs for engine are not for durability. THe very simple rules of thumb determined before WWII will take care of durability. The problem is that if you want to increase fuel effinceny you have to reduce the amount of un-need drag on the engine. The oil pump and water pump are two area's that hold a lot of potential for saveing drag. By detrmineing the flow rates needed company's can reduce the oil pump to the bare minimum needed to keep the engine alive and happy. Some companies have been playing around with variable output oil pumps and water pumps and or useing electric motors for oil and water pump functions.

Thin oil have nothing to do with increaseing an engines life cycle beyound what could be done with more traditonal viscosities of oil. It is all about reduceing fuel consumption. Even in Japan and Asia company's like Toyota are not trying to switch consumers over to thinner oils for life cycle reason it is for energy conservation. If the engine is properly designed to use a thinner oil then 85% of end user will never have a problem due to the thinner oil recomendation!

Just a point of common sense. If the engine does not need more flow then how does more flow help? It is like putting a 1000CFM air filter and intake system on an engine that can only use 500 CFM at WOT at redline. You do not gain anything by exceeding what the engine needs. Like wise HTHS has it's point of deminishing returns. Most engines used as daily drivers by most consumers do not gain much in terms of wear prevention by exceeding an HTHS of 3.6. Sure the wear rate will continue to drop but you start to lose fuel economy in some situations like short trips and cold tempatures. You might also get more initial start up wear in cold climates if the high HTHS was achived through viscosity alone. You really have to have a good comprimise with the expection of extremes outside of the norms like raceing, liveing in artic circle, heavily worn engine etc.....
 
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