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Gwood

New Oil, Old Car

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Does anyone know if you can use 5W-30 oil in a 49 dodge 6 cylinder? Is there a big difference between 10W-40 and 5W-30?

I would value your knowledge. Thanks, Glenn

Edited by Gwood (see edit history)

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I would think if you want to use a multi grade, 20/50 would be more suitable. I preferred to use Duckhams (if it's still available)

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I'm not sure about something as 'modern' as a '49 but since the car has a full pressure feed oil system and filter, you should be O.K. If you're in a hot climate the 10W-40 might be preferable.

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If the manual says 30wt then go for that. I would have suggested that for a babbit bearing engine but I suppose it's O.K. for yours or they wouldn't recommend it. Whatever oil you choose, if your engine has never been rebuilt, avoid a detergent oil - even 30wt detergent (which is great for old engines) will lift and suspend sedimentary particles; carbon, grit, etc and deliver it straight to your bearings. Frequent oil changes are a thing of the past to the modern motorist but with these old cars, I would always do it annually.

Ray.

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A very important aspect of your oil is that it must be suitable for flat tappet engines, which means it should contain ZDDP or similar. If it does not say on the pack it is good for flat tappets, look for one that does. I use Penrite, which is formulated for older engines (but still meets the latest SAE standards). I am using 20W-50 in my DB 8. SAE 30 is a very low spec: good for lawn mowers and the like and perhaps as a running in oil.

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Glenn,

I don't know where you are located but regardless, if you don't drive the car every week and it sits for a while between drives and you want to preserve the engine, consider using the Classic Motor Oil product produced by the Indiana Region of the CCCA. It costs about $65 per case including shipping and it's specially formulated for older cars (particularly the club-recognized Classics) with additive packages tailored for collector cars that are not driven regularly. A couple of multi-viscosity oils are available.

Bill

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Another thing to consider might be the valve seats on this engine. They are probably not hardened and burning unleaded gas will do them no good in the long term (I had this happen on a '65 Plymouth with slant 6, over 100,000 miles the valve seats were pounded badly and compression was way down as a result). However, if you only drive the car on occasional Sundays and miles are few, I doubt you will need to worry too much. There are lead substitute products you can add to the gasoline that are supposed to remedy this. There's a bunch of info on oils for flat tappet cams (higher ZDDP) here: http://forums.corvetteforum.com/c3-tech-performance/2484100-list-of-flat-tappet-oils.html

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Another thing to consider might be the valve seats on this engine. They are probably not hardened and burning unleaded gas will do them no good in the long term (I had this happen on a '65 Plymouth with slant 6, over 100,000 miles the valve seats were pounded badly and compression was way down as a result). However, if you only drive the car on occasional Sundays and miles are few, I doubt you will need to worry too much. There are lead substitute products you can add to the gasoline that are supposed to remedy this. There's a bunch of info on oils for flat tappet cams (higher ZDDP) here: http://forums.corvetteforum.com/c3-tech-performance/2484100-list-of-flat-tappet-oils.html

From the articles I've read a four cylinder DB doesn't have enough valve spring pressure to warrant useing ZDDP. As Rick stated straight 30 weight would be the choice. With almost no oil pressure like a DB has you need the thicker oil to coat and cushion.

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"Only a hundred thousand on a slant six, that just getting broken in!" normally yes but running unleaded gas in a high compression 'modern' engine that was designed to burn leaded will eventually have issues. I agree the 4 cylinder DB probably won't suffer from lack of ZDDP. I suspect it wasn't even added to oil back in the 1920's.

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That could be part of the reason those old engines didn't last anywhere near as long as later engines do. Other reasons include lack of good oil filtration and poor or nil air cleaners.

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Perhaps. As far as case hardening steel components, were the techniques much different then? I would think some of the durability improvements over the years were due to basic metallurgy and heat treat improvements. Lack of filtration sure didn't help.

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Hi

you cannot use modern engine oils in engines with flat bottom lifters as most of the zinc has been removed. Diesels oils either as there is too much in the way of detergants. PLease see the website for Camoils.com and everything is explained in detail. brand new rebuilds are being destroyed in just a few hundred miles because of new oils of of the store shelves. Hope that helps.

dbtimesthree

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Sounds like good advice. Even some engine rebuilders don't know about the zink missing.

Ray

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I am afraid there is a lot of mis-information out there about oil.

I have just looked at ZDDPlus™ - ZDDP for Classic, Muscle Cars & More. There are a series of technical articles on oils and ZDDP. Their conclusions in TechBrief14 " ZDDP and Pre-WWII Engines" are attached.

post-88545-143139228886_thumb.jpg

Obviously they are attempting to sell their product, but the tech briefs on the web site read very well. There is a fair bit of research behind those papers. They describe the friction of flat tappet lifters compared to modern (post about 1996) roller lifters. There is an argument about tappet pressure on the cam; you would need to work out what the spring pressure is in your old engine before accepting the comment earlier that valve springs in old motors are pretty weak. They use a fairly colloquial term for the spring pressure (x pounds): is that force on the entire lifter, or pressure per square inch (psi), and is it a force (i.e. pound-force, which is sort of a weight when vertical and includes gravity) or a mass only?

One conclusion is that using an old-style non-detergent oil is a bad idea. The dispersants only affect particles smaller than 5 microns, and they take a long time to settle in the sump. The purpose of the dispersants is that these suspended particles come out at oil change time. There is a remote possibility that sludge mobilized by a change to modern oil may build up around the pump intake. But if the engine is that full of sludge, it is rebuild time anyway. At least remove the sump and clean it out before changing. Modern full flow filters don't remove these sub-5 micron particles. Remember that Ford recommended Model T oil be changed at 500 mile intervals in summer and 300 miles in winter!

Enuff! The sun is shining. Time to take a DC wheel off and change the tyre or tire. Groan - it is not a pleasurable job.

Graham

post-88545-143139228854_thumb.jpg

Edited by Spinneyhill (see edit history)

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With almost no oil pressure like a DB has you need the thicker oil to coat and cushion.

What years are you thinking of, Doug? My '32 consistently shows about 40 lbs. of pressure, even at idle. I'm using 30 weight non-detergent.

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Phil,

I think what Doug was refering to was the early DB's show 4/5 lbs on the oil gauge as does my "23" but my "31" runs around 30 lbs.

Joe C.

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