10W-30 0r straight 30W? Why not 10W-40?

[motoman]

Craftsman owners manual allows 5w-30 which I use. It throws out a little which is good in my opinion. Interesting what JD says about the hot spot near the exhaust valve on AC engines. I have (in this forum) attempted to measure the temp of the exh valve guide casting on my 24 Intek, but could not get a good heat transfer to the K probe. I have measured 312F with a head probe under the spark plug. My theory (forum browsers tune out) is that the "creep" temp of 390F was reached on my rider which pushed the exh guide into the head. Since adding gauges and an oil cooler I know when it's too hot to keep mowing (sump oil 290-300F).

Oil is like politics...but my read says go with thinner oil for cooling as there is more throughput per unit time. The Intek holds 30PSI at indicated 290F oil, but is not runaway (it stabilizes with the cooler). The read also said the additive pak that goes away with heat/time affects the thinner and that is visible by the time I change the oil (5W-30 Chevron) which is much thicker than new. Perhaps it is the additive pak people are referring to when they inevitably say "breakdown" without defining it.

 

[Fish]

Don't know about the politics or semantics involved, but a cooked engine destroyed due to 10w40 breakdown is one that you won't forget.

The engine usually has adequate oil level, and oddly enough either the rod or the lower bearing is the one that seized. The messy goo in the crankcase is hard to remove, straight gas and brushes usually is the best, but why? As the bottom sump/bearing is toast as well as the crank.

The oil industry may have improved the 10w40 oil in the last 10-15 years, while they were not throwing the world in a recession {that approached
the "Depression" word}, and if they have, I don't know about it.


But 10-20 years ago, 10w40 multi-viscosity breakdown was a common
problem........

So I still advise against it.

 

[motoman]

fish, definition , please, of "breakdown"

 

[KennyV]

The misinformation is only going to be exceeded by decades Old, partial information...

 

[exotion]

Breakdown occurs when the life span of the oil is used up it loses lubricating properties no? I've never heard of oil sludge unless someone hasn't changed oil in like 20 years...

 

[Brucebotti]

Don't know about the politics or semantics involved, but a cooked engine destroyed due to 10w40 breakdown is one that you won't forget.

The engine usually has adequate oil level, and oddly enough either the rod or the lower bearing is the one that seized. The messy goo in the crankcase is hard to remove, straight gas and brushes usually is the best, but why? As the bottom sump/bearing is toast as well as the crank.

The oil industry may have improved the 10w40 oil in the last 10-15 years, while they were not throwing the world in a recession {that approached
the "Depression" word}, and if they have, I don't know about it.


But 10-20 years ago, 10w40 multi-viscosity breakdown was a common
problem........

So I still advise against it.

I agree. I can't remember exactly when in the past, but GM claimed that they would not honor warranties if 10w-40 oil was used.
Bruce

 

[afoulk]

Breakdown occurs when the life span of the oil is used up it loses lubricating properties no? I've never heard of oil sludge unless someone hasn't changed oil in like 20 years...

It was the viscosity improvers added to the oil to get it from the 10 weight up to the 40 weight when hot that would break down in extreme conditions and cause sludge, varnish, and loss of protection. That's why synthetics would withstand heat better, they required less viscosity improvers to reach that viscosity spread. Generally speaking, the closer those numbers are to each other, the more resistant they are to shearing and breakdown, for example, 5w20 is a thin oil, but rarely shears down out of spec. Same with 10w30. But take a 5w30, and by the end of an oil change interval, it might shear down to a 20 weight oil anyways. Technology had improved so much in the past 15 years or so that this isn't really much of a problem any more. I've been running regular oil in my stuff for the past three years with out a problem now and in fact, i'm using Valvoline maxlife 10w40 in my lawnboy right now and it hasn't blown up yet and honestly, unless your using a more expensive "boutique" oil like amsoil or redline, your "synthetic" oil isn't really a true synthetic anyways, just a highly refined group 3 or 4 dino oil. The big companies like Pennzoil or Valvoline used to make true synthetics until everyone caught on to what castrol was doing with their syntec line, there were lawsuits involved and the government wound up ruling in castrols favor, now no one makes a true synthetic since honestly, the higher end Dino base oils work nearly as good,b and its cheaper for them to produce.

 

[motoman]

Sludge is also formed by insufficient operating temperature. Strange I would talk about not enough temp, but the oil contains condensation (water) which should be driven out by oil temps of 200-220F. I take a lot of care not to make short runs with my beloved Intek. Another reason to have an oil temp gauge . As a lowly homeowner it takes patience in fall or faced with only a few hauling tasks to get to operating temp, but I strongly suggest it.

I have a V6 Fiero , 1985, engine never apart. Have always run 10W-40 in it.

 

[Fish]

No, when tearing down an engine, when you find a burnt smelly, sticky goo pasted over everything that straight gas will barely even cut, it is
from broken down oil. Usually I find out that the user uses 10w40, many folks don't know. Many times the bottom bearing seizes, even when the engine is full of oil, sometimes the lower rod on a twin.
Whether or not the oils have changed or not in the last 10 years, I don't know, but I doubt it.

Of course synthetic is another topic altogether, but as far as the worst offenders of multi-viscosity breakdown is dino 10w40.

 

[motoman]

No is very strong. Let us define a little. Sludge , I guess can be seen as several things. So called varnish also. Overheated oil, ? 300-340F? will cause deposits ( perhaps a better term). Fish , I know you have seen many where I have not, but AC tractor engines are notorious for valve train failures also. Some of that is allegedly caused by deposits in the valve guides which cause the valve to seize momentarily and bends pushrods, causing them to drop out. I have personally seen sludge in auto (water cooled) engine valve covers where it was thick as mayo due to short runs and insufficient warming. Actually both sludge and varnish are really undefined and catch-all words like "pain." I am not surprised at seized and broken big ends sitting in what appears to be sufficient oil level....er, where were we? motoman