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Old 08-25-2013, 07:51 PM   #1
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changing oil weight

the guy i bought the car off of told me to put 20 w50 in, and that seems really heavy for a 84 350. im wondering what kind of oil you put in your 350, and if changing to a lower viscosity would harm the engine in any way. i've alway heard that changing the viscosity will blow up your engine, but i dont understand how. if somone could explain, that would also be helpful. i do have to crank the starter for a good 4 seconds during a cold start, wich might be from the heavy weight oil...
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Old 08-26-2013, 07:32 AM   #2
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Re: changing oil weight

Basically everything in that post is a collection of old myths and legends that were never very accurate but are now totally obsolete.

"84 350" has nothing to do with it.

Quote:
i've alway heard that changing the viscosity will blow up your engine, but i dont understand how

That's good, because it CAN'T.

I'd suggest ignoring all that stuff; the PO, whatever you've "heard", and so forth. Put in what it says on the oil cap, which if memory serves, is 10W-30.
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Old 08-26-2013, 09:56 AM   #3
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Re: changing oil weight

The previous owner may be trying to hide something.
Using 20W50 is one way to get oil pressure up on an engine that has low oil pressure.
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Old 08-26-2013, 11:01 AM   #4
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Re: changing oil weight

Ever seen oil when it's hot? it flows like water.

Despite when hot all oils will "flow like water" a heavier weight oil will "cling" better to moving parts, even when hot.

That being said 20W50 is used in a racing engine for that reason, (high heat, high RPM, better clinging oil to moving parts)

NASCAR uses MOBIL 1 synthetic 20W50 for the same reason but even better high temp protection (think 7000+ RPM for 500 miles)

Production cars do not always need this extreme level of protection, and most people you use what the owner's manual tells them for best performance. fuel economy, & emissions. Most new cars use a lighter weight oil ( 5W20 ) simply for better fuel economy. but 5W30 even 10W30 will be fine./

BUT if you have an older car the owner's manual, it used to have an Oil viscosity to Ambient temp air chart... I know the manual in my '88 does.

This chart shows the range of oil you can use, based on the ambient temp.
20W50 is on the chart, but should not be used when colder the 40 degrees.

If you look at owner manual from now and 25 years ago.. they really dumbed them down, and it's all about fuel economy, not a bad thing but no one oil can do all things which is why they make different weights... A heavier weight oil (when cold) is harder to pump but will hold up better to high temp hi rpm use.

If you are changing oil every 3000 miles in a street cat it does not matter... run cheap oil and use a good filter. if you want extended service or don't drive much run synthetic or good conventional oil and a premium filter.

10W30 is the norm & 5W30 for autumn & winter

Synthetics are a whole other animal, because they will pump at a much lower temps than conventional oil.
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Old 08-26-2013, 11:11 AM   #5
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Re: changing oil weight

http://www.12v.org/maintenance/index...ection=ss&ss=4
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Old 08-26-2013, 06:21 PM   #6
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Re: changing oil weight

case in point for my drag car:

Break-in oil was straight 30 weight.

Once broken-in I have run 10w-40 or 20w50.



The family car uses 5w30 synthetic year round as per the Mfg. specs. Service schedule "B" oil & filter change every 8,000 miles or once per year. My wife is lucky if she drives 7,000 miles year.

My work vehicle 5w30 conventional per Owner Manual Service schedule "A" changed every 3000 miles. Average 15-20K miles per year. still runs.

Base your choice of oil on 2 factors... 1) the type of driving you do & 2) what the owner's manual says (or the engine builder tells you to use)

The rest is just that.. "the rest"
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Old 08-26-2013, 07:45 PM   #7
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Re: changing oil weight

My car has reached oil stasis.

I have to add a quart every so often, so I figure I never need to actually "change" the oil.

Its "self-changing." Click the image to open in full size.
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Old 08-27-2013, 07:22 AM   #8
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Re: changing oil weight

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Originally Posted by W.E.G. View Post
My car has reached oil stasis.

I have to add a quart every so often, so I figure I never need to actually "change" the oil.

Its "self-changing." Click the image to open in full size.
just change the filter every 3000 miles

Seriously though if it's not burning it, where is it going? On your driveway? How many miles between topping off?

Did you try switching to a heavier weight oil?

Last edited by FRMULA88; 08-27-2013 at 07:42 AM.
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Old 08-27-2013, 05:56 PM   #9
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Re: changing oil weight

That side conversation isn't particularly informative to the OP, who wishes to talk about HIS oil.

And who I still advise, IGNORE all the crap you see on forums and hear at Friday night McDonalds parking lot monkey-spank sessions. Put into the motor what it says on the oil cap and in the owner's manual. Believe it or not, those other "sources" (I use the word VERY loosely) don't "know" "more" about oil, than the people who designed the engine did.
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William of Ockham, c. 1330 AD, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi

Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

The simplest explanation that fits all the facts is probably the right one.
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Old 08-28-2013, 12:59 AM   #10
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Re: changing oil weight

My engine builder swears by Shell Rotella 15w40, same as he puts in his 1000 hp diesels.

Personally I doubt it matters much as long as you change it regularily; 5w30 is probly a little light for extended high-speed operation.

20w50 could possible blow an oil filter right off if fired up to 3000 rpm in -20-degree weather.
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Old 08-28-2013, 03:29 AM   #11
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Re: changing oil weight

The only thing which may even be a myth. I have been told do not switch between synthetic and conventional that could cause some issues. Never tried it and never heard hard core confirmation on this statement. I bought my car in 1997 with 57k on the clock. First thing was a tune up and an oil change I started using Mobil 1 15w50 synthetic and have never stopped using the same oil. She clocking 162k now and still runs great. The only issue you would probably have when it came to oil weight would be in a little 4 banger. the returns aren't as big and plentiful like the v8 and could possibly starve it of oil when going a thicker weight.
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Old 08-28-2013, 07:22 AM   #12
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Re: changing oil weight

I always liked this article http://www.bobistheoilguy.com/motor-oil-101/
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Old 08-28-2013, 08:48 AM   #13
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Re: changing oil weight

and I quote;

"These engine blocks are kept at around 212F all year round. The oil is around the same temperature as well. This allows for a single grade oil all year round.

Bovine Feces... how is an engine block kept at 212F all year round when it sits outside in -30F degree weather ? this is when you want an easy pumping oil.. like 5W- conventional or synthetic...



" this is not the same as on the track where the coolant temperature is slightly higher and the oil temperature is much higher "


Some more bovine feces.. what is this man;s racing credentials..?!

At the dragstrip coolant temps and oil temps are typically in parity.. if coolant is at 160-180 so will the engine oil ..


Follow the Owner's manual for OEM cars.. the Engineers that designed the engine know a heck of a lot more than some "CYBER MECHANIC"

For "race cars" you follow the engine builder's or crate motor MFG. recommendations..
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Old 08-28-2013, 12:03 PM   #14
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Re: changing oil weight

The only reasons I can think he said that was:

1) the engine is wore out and clearances are such that 10w30 oil isn't cutting it anymore and he's trying to get a little more life out of the car
2) he actually knows a tiny bit about the oil and knows that *SOME* 20W50 oils still have enough zinc / zddp to protect old flat tappet cams...

SO - I would simply run a good quality oil in the recommended weight that contains enough zinc/zddp to keep the flat tappet engine healthy... Stock cams with stock springs and a lazy ramp profile can get away with lower amounts of zinc then say breaking in a 'race' cam with an aggressive profile...

Check your favorite oil brand's website for information - some have it posted, some don't... Valvoline VR1 'racing' oil that was on the shelves at parts stores had enough in there last I checked and they had the detergent package to be ok for a street engine... Castrol GTX 20W50 and HD30 had enough zinc for flat tappet cams (although a little light for break-in IMHO since they cut it in half a while back), etc.
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Old 08-28-2013, 12:29 PM   #15
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Re: changing oil weight

true, however roller cams don't need the same amount of zinc additive.

break-in oil has to have more zinc to allow for proper break-in.

Check out Brad Penn Oils ..
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Old 08-28-2013, 07:55 PM   #16
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Re: changing oil weight

I would keep using the recommended oil weight. When you start to burn oil I would go to the next weight. This has worked for me. Also buy some ZDDP and add it to each oil change. I also use Lubri-Moly oil bought from ECS tuning. Its imported from Germany. Has more anti wear additives. I've been sending samples at every oil change to Blackstone labs for analysis. Their recommendation is to change the oil at 12000 mile interval. This is on my other car though (R32). 20w 50 will only protect your engine when at proper engine operating temp. So at cold startup the oil is so thick it wont protect your internals as well.

Last edited by 426 Wedge; 08-29-2013 at 01:59 PM.
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Old 08-28-2013, 10:03 PM   #17
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Re: changing oil weight

I's stick with the recommended viscosity that is typically stamped on the filler cap. Mine reads "5w-30". Use any brand name oil that meet the latest API Service level (I think they're up to SN).

I highly doubt you'll be doing any harm with running 5w-30 vs. 20w-50.

You're engine is an '88 so it should have a roller cam; You don't need ZDDP or any other additive.
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Old 08-29-2013, 05:27 AM   #18
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Re: changing oil weight

when in doubt, go with 10W-30... if it has good oil pressure and doesn't make any weird noises, try 5W-30..
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Old 08-29-2013, 07:29 AM   #19
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Re: changing oil weight

Quote:
Originally Posted by FRMULA88 View Post
true, however roller cams don't need the same amount of zinc additive.
Quote:
Originally Posted by paulo57509 View Post
You're engine is an '88 so it should have a roller cam; You don't need ZDDP or any other additive.
In his post he specifically says "84 350" - so I assume that the engine that is in there isn't the factory engine but the '84 he lists in the first post. If it is an 1984 350 engine then it's a 2-pc rear main seal and none that I knew of ever had a factory roller cam...
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Old 08-29-2013, 08:35 AM   #20
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Re: changing oil weight

Quote:
Originally Posted by Copperhead View Post
My engine builder swears by Shell Rotella 15w40, same as he puts in his 1000 hp diesels.

Personally I doubt it matters much as long as you change it regularily; 5w30 is probly a little light for extended high-speed operation.

20w50 could possible blow an oil filter right off if fired up to 3000 rpm in -20-degree weather.
I love shell rotella T, I use it in my TA and two of my motorcycles. It also comes in 5w-40 synthetic and 10w-30.

I have recently email shell and it still has over 1200ppm of ZDDP for flat tappet cams.
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Old 08-29-2013, 08:56 AM   #21
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Re: changing oil weight

Quote:
Originally Posted by bwiencek View Post
In his post he specifically says "84 350" - so I assume that the engine that is in there isn't the factory engine but the '84 he lists in the first post. If it is an 1984 350 engine then it's a 2-pc rear main seal and none that I knew of ever had a factory roller cam...
I was using his profile as reference.

I still don't think ZDDP or additives are necessary.

Last edited by paulo57509; 08-29-2013 at 09:01 AM.
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Old 08-29-2013, 10:30 AM   #22
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Re: changing oil weight

If you're concerned, I'd measure the oil pressure and then decide. Don't trust what an electric dash gauge says, they frequently aren't accurate. Use a mechanical gauge instead. I'm not sure what the oil pressure spec is for that engine, but find out and compare. Check it when oil is fully warmed up (this takes longer than heating up the coolant). At that time the oil pressure will be at it's lowest and can be compared to the spec at whatever RPM is called for.
Even when new, the viscosity spec was a compromise between different interests, one of them being fuel mileage. The engine is near 30 years old, that's a lot of time for bearing clearances to change. I wouldn't use 20w50 unless it really needs it, but if it needs it then at least you'll know.

Cold viscosity is a concern. Be easy on the engine until it warms up, it's not lubed well when the oil is still cold and thick. Try not to run 20wAnything if you don't have to.

I'd probably use Valvoline VR1 conventional, whatever viscosity you decide you need. It's closer to the ZDDP that all mainstream oil had when that engine was designed. They have 10w30 and 20w50, and you can also mix them to make what's essentially 15w40.
There's also Rotella, I don't know much about it.
You could also use Quaker State Defy, which is available in 5w30 and 10w40, which you can't get with VR1. The 10w40 version is higher in ZDDP than the other versions, because API doesn't regulate 10w40 the same. The Xw30 versions of Defy stay within limits from the early 2000s. They want it to be marketable to cars that call for API SL.
VR1 10w30 doesn't care about that, so they rated it API SH (~1994) and put what they want in it.

Any reputable brand name oil of reasonable viscosity will basically work, people just have different opinions about what's best for longevity. Under normal circumstances none of it is going to do anything obvious to the engine. Now if it has seriously low oil pressure, then that would be an abnormal situation.
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Old 09-01-2013, 01:25 AM   #23
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Re: changing oil weight

Quote:
Originally Posted by armos View Post
If you're concerned, I'd measure the oil pressure and then decide. Don't trust what an electric dash gauge.....
Hes right about excessive bearing clearance. In my case my oil gauge would max out and run at 60+psi under acceleration. Sometimes, 30 which is normal. One day after the oil heated up my psi dropped to 0psi at stop lights or idle. Then peak at 15 psi while driving. Ive read 15 is enough, but fix the problem.
It can be a few reasons

1. Clogged screen for your oil pickup line. (Remove oil pan and inspect)
2. Weak oil pump. (If so, remove oil pan, get the Melling High Volume oilpump. Its stock pressure but better flow.)
3. If none of the above then it is excessive main bearing clearance, you must remove the oilpan, and replace bearings.


I was able to get my oilpan off with the manual trans still attached, motor in car, and hood on. Turn the motor to 180degrees. Used a come along to lift the motor, after suspending it removed the motor mount bolts. Raised it 3 inches eye to eye off motor mount. If you didnt get the motor timing set right when you goto pull the oilpan itll get hung up on the front counterweight on the crank. After removing the pan youll be able to access the main bearings and they slide right out!
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