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Old 04-29-2008, 04:48 PM   #1
salazar44
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Oil Weight

What type of oil weight are you all running? I broke my engine in with straight 30 weight (no detergents) as suggested from the company I got the engine from. Now Im looking to flush it and put standard oil in. So... What weight? and 5 qts?
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Old 04-29-2008, 05:18 PM   #2
ChiefRocka
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Re: Oil Weight

Personally, I run 10w40 on new engines, and 20w50 on older engines.

I have no idea of the mileage in my truck, and how the PO treated it, so I am running 20w50 which is giving me great oil pressure.
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Old 04-29-2008, 06:09 PM   #3
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Re: Oil Weight

Thanks dude... I will see what others say as well. Not that your word isnt good... I just know there are tons of different standpoints on oil weights.
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Old 04-29-2008, 07:36 PM   #4
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Re: Oil Weight

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Thanks dude... I will see what others say as well. Not that your word isnt good... I just know there are tons of different standpoints on oil weights.
Of course....What does the engine supplier/builder recommend ?
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Old 04-30-2008, 01:20 AM   #5
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Re: Oil Weight

Good idea... I will give them a call!
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Old 04-30-2008, 01:29 AM   #6
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Re: Oil Weight

interesting... he said to run 20-50. Funny thing... i dont think i have ever noticed that weight while oil shopping. LOL.. I guess Im usually focused 10-30w
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Old 04-30-2008, 06:07 AM   #7
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Re: Oil Weight

guh, guess i should do a change then! lol.....maybe why i got a leak now too!
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Old 05-01-2008, 01:21 AM   #8
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Re: Oil Weight

Since you're in socal 20W-50 should work fine. I run it in my 52, but it's too thick in the Kansas winter. I buy it at wally world or the parts store.
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Old 05-01-2008, 01:45 AM   #9
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Re: Oil Weight

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Since you're in socal 20W-50 should work fine. I run it in my 52, but it's too thick in the Kansas winter. I buy it at wally world or the parts store.
x2 that! IMO 20w-50 is also too much for those running high volume pumps... cold weather plus HV pump= lots of stress on distributor/cam gears.
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Old 05-01-2008, 02:36 AM   #10
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Re: Oil Weight

I run 10W-30 and add 1 quart of Lucas Oil Stabilizer. If I go to school in New York next year, I will take my jeep and only run 10W-30
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Old 05-01-2008, 07:28 AM   #11
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Re: Oil Weight

I use 10W-30 myself. 20W-50 is okay too and does help oil pressure if your clearances are a bit wide.....

10W-40 is an odd one. The chemistry necessary to have this large a viscosity swing also effects it's ability to lubricate. My brother's in the oil business which has made sense of a lot of this stuff for me.

Most engine wear occurs on startup, so I figure a lighter oil will be able to start lubricating faster. For you guys in cold climates, and oil pan heater (magnetic) can be a real help on cold mornings and will do a lot more to reduce wear than a block heater.

At work I sometimes get to work around some big machines that have a separate oil pump which is run prior to the equipment actually starting (pre-oiling).

Oh, and frequent oil changes are worth a lot more than fancy schmancy oils. Compared to the 60s technology in our rigs, modern oils are fantastic.
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Old 05-01-2008, 07:35 AM   #12
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Re: Oil Weight

ok, so could someone break down the numbering behind oil and its weight
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Old 05-01-2008, 07:49 AM   #13
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Re: Oil Weight

Sure. The whole scale for engine oils is just arbitrary. That's why you can see 0W-30 oils, which theoretically shouldn't be possible if the numbers had a real meaning.

The higher the number, the thicker the oil (higher viscosity). Now, all by itself oil will change viscosity based on temperature (30 weight when it's cold is molasses in January)

So, when the engine is at operating temperature (well, really the oil is at temperature), we want something around a "30" weight oil. But, when the engine is cold (startup, or January), the oil is very thick and hard to pump effectively. So, it used to be that folks would switch to a lighter oil (say 10) in the winter. But this really isn't ideal either. Now, some clever chemists figured out a way to have an oil behave like it was 10 weight when it's cold (thus approximating a 30 weight when it's at normal temp), and a 30 weight when temperature is normal. Pretty much ideal.

One other thing... gear oil (say 80W-90) actually uses a different arbitrary scale. So, it's not fair to say that a 90 weight gear oil is three times as thick as 30 weight motor oil.

Now you've got me wanting to look up how 30 was picked as the standard number....
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Old 05-01-2008, 08:15 AM   #14
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Re: Oil Weight

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Now, some clever chemists figured out a way to have an oil behave like it was 10 weight when it's cold (thus approximating a 30 weight when it's at normal temp), and a 30 weight when temperature is normal. Pretty much ideal.
An aquaintance of mine who is also in the oil business explained that clevorness to me in what I am sure is oversimplified layman's terms, but it made sense.

The oil molecule in the multiviscosity oil is like a coil. When it is cold the coil shrinks and is short, and when the oil is hot the coil stretches out and is long.
When the coils are long they tangle up with each other, that is what makes the film strength, they don't want to separate and so stays between the metal parts. When cold and short, they don't tangle up with each other as much, hence they are more "willing" to move along and flow, but they also don't have as much film strength.

The problem with multiviscosity oil, the reason you want to change it fairly frequently, is that with use those coil molecules get broken up. YOu end up with only short pieces, given long enough your 10W30 turns into simply 10.

I'm not the expert here, that is how it was explained to me, and I bought it hook line and sinker.
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Old 05-01-2008, 11:03 PM   #15
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Re: Oil Weight

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The problem with multiviscosity oil, the reason you want to change it fairly frequently, is that with use those coil molecules get broken up. YOu end up with only short pieces, given long enough your 10W30 turns into simply 10.
Speaking in those terms, I heard that synthetic "breaks down" quicker then conventional. What does your buddy have to say about that? Also... is it okay to use synthetic oil in my 350? I think its from like a 74 camaro. I heard that early synthetic oils broke down seals quicker.... or something like that. Currently I use synthetic in my new cars but wasnt sure if I should just stick with conventional for the old guy.

Thanks for all the help!
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Old 05-01-2008, 11:09 PM   #16
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Thumbs up Re: Oil Weight

I use 10W-30 doesnt get really cold here in NorthWest Arkansas for long amounts of time during the winter.Its new 283 bored 0.030

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Old 05-01-2008, 11:15 PM   #17
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Re: Oil Weight

I run straight 40weight as recommended by the guy who did the machining on the motor.
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Old 05-02-2008, 03:19 AM   #18
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Re: Oil Weight

I run 15w-40 Diesel oil. Since roller cams became the norm in the last 10 years modern oils don't have as much protection against sheer load on the cam caused by regular hydraulic lifters. Diesel oil has more protection that conventional car oil because it is built for a more extreme environment.

I think synthetic is great for modern engines with close tolerances, but for our old tech rigs the seals are not precision enough to prevent leaks, especially on an engine with more than 50k miles on the seals.

Also, my understanding of the weights is that 10w-30 is always a 10 weight, it just has the heat resistance of a straight 30 weight and the flow capability of a 10 weight. In other words, it doesn't get thicker as it gets hotter.
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Old 05-02-2008, 05:27 AM   #19
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Re: Oil Weight

Before they started adding polymers to oil, the SAE # was the lowest recommended temperature for running the oil. SAE 40 was good to 40*F.

When polymers were added, the oil became good for multiple viscosities. These oils included the letter W. The more polymer added, the greater the range, but the less lubricant in the oil. So adding more polymer came at a high price.

In the 70's GM figured out that the 10W-40 oil did not have enough lubrication, and engines were failing. So your failed engine was not under warranty if the oil test from the lab showed you were running 10W-40. Since then, the polymers have improved and 10W-40 is again acceptable.

Attached is a chart from SAE showing the bottom temp ranges for multi-viscosity motor oils.
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Old 05-03-2008, 07:32 AM   #20
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Re: Oil Weight

Thanks, Fred, good information. You jogged my memory with the chart about the # values. And Tom, you're right about the diesel oil. It has additional zinc that acts as a lubricant for the cam lobes and lifters. Seems to me the manufacturers have been trying to lower the zinc content because it causes trouble with the catalytic converter (coats the metals, I believe).

About synthetic, there's no doubt it's better, but my experience has been pretty lack-luster. The damn stuff was so slippery, it all leaked out of my old engine... Plus, where synthetic really shines is racing (or other high loads), where you've got high RPM plus high operating temperatures (think mandatory oil cooler). I don't know about you guys, but that's not my truck. I lug the engine on long mountain climbs pulling a trailer, but that's relatively short duration, and the oil doesn't get that hot. For my money, I'd rather change conventional oil more frequently than use synthetic.
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