oil weight

[shadango]

So while I was out at Walmart, I inadvertently picked up 10w40 rather than 10w30 oil.......its a synthetic blend by valvoline for high mileage engines.

Using it in my 92 Dakota 318 and my fish's 318 -- its a 1976 block. For the fish I plan on adding zddp.

Seeing as these vehicles are run mostly in the spring/summer/fall, seems like 10w40 should be fine for both  right???

Dont want to overthink it.

The chilton manual for the Dakota (from back in mid 1990) doesnt even list 10w40 in the oil chart......

[cudabob496]

At startup, it will take longer for 10w-40 to reach remote areas of your engine, like the
valve train, than 5w-30. Start up is when most engine wear occurs. I use 5w-30 fully synthetic in my 496.
and unless you have oil pressure problems due to bearing cleanrances, 40wt is unneccesary, and wastes
horspower.

[734406pk]

I have used both in these engines without any problems. 10w40 would be preferred in hotter weather(85deg +) . It will rob some hp from the engine, but I would expect it to be minor. If your not racing and just cruising I wouldn't be concerned.

[Strawdawg]

The 30 and the 40 wts are measured at 100 C or 212 F which is in the range of a typical warmed up engine oil temp

On a typical start up, the difference is minute between the two.  On a hot engine the 10w-40 will have a slightly higher oil pressure which takes a little more power to turn the pump.  It probably won't show up on a dyno due to the ability of the dyno to read such small variations with precision but it will be there-might cost you a hp or two.

If your engine has a few miles on it, it might bring the pressure back to where it was when new with the 10w-30.

I would not worry about it in this case.  There is practically no load on an engine at start up and the actual viscosity difference between the two at start up oil temperatures is so small to be almost imperceptible.  Modern oils do not drain off surfaces and leave them dry, anyway.

[OUTLAW]

I agree with Strawdog

[brasil]

..in my owner manual it says   even 20w50 is recommended, if the engine is " raced"  or under heavy conditions...

only the  20  W  makes me a little confused... thatoil would be like honey...if the temp is below 40 deg or so...

Greetings Jurgen

[Strawdawg]

..in my owner manual it says   even 20w50 is recommended, if the engine is " raced"  or under heavy conditions...

only the  20  W  makes me a little confused... thatoil would be like honey...if the temp is below 40 deg or so...

Greetings Jurgen

Jurgen, the manual was written 40-50 years ago and a couple things are probably different today,

First, the quality of engine assembly was far less precise in general than it is today.  Engines often had looser clearances and the crankshaft/crank saddles may have not been as straight as today.

Second, the quality of the oil was not nearly as good as it is today, and oil could, and did, lose its viscosity with age when it got hot.  It was not uncommon at all for heavier oils to be suggested for high performance use.

Today's oils last much longer and their characteristics are much more stable.  It is very rare today to need 20w-50 oil in a street car, or any other, for that matter.

Typically, if the engine, after being run hard, still shows close to to the old 10 psi per thousand rpm rule at peak rpm, it is heavy enough.  Many pure race engines run less than that.  Low rpm oil pressure is usually not sensitive because there is no real load on the engine parts at idle, or cruise.

A 20w oil flows like a 20 weight oil at -10 C.  At colder temps than the rated temp, a quality synthetic oil will flow better than a conventional oil does below its rated temp.  If you live up north where it gets really cold, then a synthetic oil will flow much better at -30 or -40 C than will an equivalently rated conventional oil.

Synthetic oils are not all equal.  A good synthetic oil will be listed as a Group IV oil and it needs very little viscosity improvers compared to cheaper synthetics like most Mobil 1's which are now Group III's with a few exceptions.  Group IV synthetics cost more.

Running a heavier oils can actually cause more engine wear because it takes much more effort to push the oil thru the engine and they take more hp to do it.  Add a hv oil pump and it gets much worse  because one is trying to push a greater volume of oil thru the same clearances which raises oil pressure while increasing the effort to do so.

That's the reason it is suggested to use a stronger oil pump drive rod when using an hv pump....so it won't shear off.  Now if the engine was built with very loose clearances, it may take an hv pump to get the desired oil pressure.

In your case, if you are turning 6000 rpm max, I would run the lightest oil possible that will still give you 60 psi at 6000 rpm on a hot day when the engine is fully hot.  That might mean you run a lighter oil in the winter and a heavier oil in the summer....if you have a big temp variation seasonally.

[cudabob496]

The 30 and the 40 wts are measured at 100 C or 212 F which is in the range of a typical warmed up engine oil temp

On a typical start up, the difference is minute between the two.  On a hot engine the 10w-40 will have a slightly higher oil pressure which takes a little more power to turn the pump.  It probably won't show up on a dyno due to the ability of the dyno to read such small variations with precision but it will be there-might cost you a hp or two.

If your engine has a few miles on it, it might bring the pressure back to where it was when new with the 10w-30.

I would not worry about it in this case.  There is practically no load on an engine at start up and the actual viscosity difference between the two at start up oil temperatures is so small to be almost imperceptible.  Modern oils do not drain off surfaces and leave them dry, anyway.

I think the difference at startup, as far as how fast the oil flows, is somewhat significant, between a 5w-30 and a 10w-40. I ran 10w-40
in a Honda Accord for a while, and would hear the valves chatter for a second or two, at startup, before they became silent.  5w-30 eliminated that issue.

[cudabob496]

Question?
You go out to start your car, and its 60 degrees out.
which of these oils will flow quickest to all areas of the engine, and give
the best protection against metal on metal wear on startup?

0w-30
5w-30
10w-30
10w-40
20w-50

Check out first two paragraphs below:

http://www.upmpg.com/tech_articles/motoroil_viscosity/

[HP_Cuda]

I agree with Strawdog - oils are weighted for temperature and should be used accordingly. If there are pressure issues then further investigation might be needed (pump, pan, pickup, etc).

You don't see folks running 90W in their motor cause they want some crazy pressure or magic metal wear suppressant.

[734406pk]

Excellent accurate information from very knowledgable people is was makes this site number one!

[Strawdawg]

That was the article where I picked up the temperature ratings for the W flow ratings..I read the entire article

I don't know anything about Hondas, but, ticking lifters normally occur when the lifters bleed down which should not happen very quickly.  An oil filter with a properly working anti-drainback valve should keep the the oil galleys full of oil so that the lifters are pressurized as soon as the engine cranks....

[cudabob496]

That was the article where I picked up the temperature ratings for the W flow ratings..I read the entire article

I don't know anything about Hondas, but, ticking lifters normally occur when the lifters bleed down which should not happen very quickly.  An oil filter with a properly working anti-drainback valve should keep the the oil galleys full of oil so that the lifters are pressurized as soon as the engine cranks....

But the point is the ticking essentially went away with the lower viscosity oil.  I imagine if you put 10-40, in a new Honda that takes 0-20, then you would
have some protection problems, but the 0-20 is for engines with tighter clearances.

I did just replace a cam and oil pump in an LS1 engine. I was very nervous about startup, since the engine and oil pump was not primed, and the cam jornals did not have much oil on them, due to the way the cam was installed, and due to me spinning the cam several times during the install, to verify valve train working properly. So, to maximize protection during startup, I filled the engine with 0-30w full synthetic.  Though is seemed like an eternity, the oil pressure screamed up after about 1 sec.  Had I put 10w-40 conventional in there, I'm guessing it would have taken another second or more for oil pressure to come up.