Type of oil

[speedyshark]

Just wanted to ask what type and grade oil would be good to use in the flat 6? I have a 48 d24 and was going to do an oil change ( first time since bought car) it has a small leak so was wondering if I should just use a thicker oil? Maybe a straight 40w or ??? I live in San Antonio Tx so not that cold here.

[Robert Horne]

I have been using 10w-40w in my 48, and my 38 for many years.

[54Illinois]

SAE 30 from Citgo. 700-800ppm of zinc.

[desoto1939]

These engine were originally design for single 30 or 20 weight oil. If you have an older engine and it has not been rebuild then I woud not recommend a multi viscosity oil such as 10W40 or 10w30. This is a detergent oil and the use of this will loosen the sludge that is built up inthe old engine.

Does it have a filter onthe engine. Is there any indication on when the oil was last chnaged and also what was used in the engine.

If old engine then I would recommend straight wieght 30 oil. But this is my suggestion only. Other will chime in.

Rich Hartung

desoto1939@aol.com

[speedyshark]

Just ordered the filter, it is the stock one and I know it has not been changed in over a year. PO passed away about a year ago and it had been sitting since then. Was thinking that maybe 40w since it has a small leak, but might just try 30 and go from there.

[desoto1939]

Ok. Where is the leak that you have found. Switching to a heavier oil will not stop the leak. If a gasket is going bad then the break inthe gasket will get worse over time just as in a modern car.

Find the leak and fix the leak.

Again puttin on a filter on the car that did not have a filter and used straight weight oil you will have a build up of sludge in the oil pan. The use of a detergent wieght oil 10w-xxx either 30/40 is a detergent oil will cause the sludge to breakup.

Stay straight weight oil until you rebuild the engine and then go to a multi weight oil. You will have an clean sump pump and oil journels and a new engine that can handle the 10Wxxx oil.

Rich Hartung

[Rusty O'Toole]

From my 1951 Plymouth - Dodge - DeSoto - Chrysler owner's manual, here is what the factory recommended:

Not lower than +32F - SAE 30

As low as +10F - SAE 20W

As low as -10F - SAE 10W

Below -10F - SAE 5W

About this time (1951) multi grade oil became available for the first time. It quickly became the default choice in all gas stations, service stations and dealerships. Chances are your car has never used anything else but 10W30, multigrade, detergent oil.

Shell Rotella 15W40 is another good choice especially in hot weather.

Thick oil will not cure a sour motor.

PS This answer is correct for a FLATHEAD six. If you actually have a Subaru, Porsche or Corvair with a FLAT six, it may be incorrect.

[speedyshark]

You mean the Porsche motor in my 48 is not stock?

Sorry meant to say flathead 6. Would flatly be ok to say? Just asking.

The car does have a stock oil filter on it. Seems a good choice to go with 30w since the car is all stock and has not been touched.

[Robert Horne]

I have had a couple negative expierences with 30W oil.

After coming home from Vietnam, 1970, I bought a 1966 Plymouth from my Aunt, 40,000 miles on it.

The car had nothing but 30W Quaker State oil, at 3000 miles changes.

At 42,000 miles, I was changing the oil, and new valve cover gaskets.

Under the valve covers was so much almost dry sludge, I could barely see

the valve springs. I dropped the oil pan, and the same situation was there. The screen on the oil pump was in very bad shape. No amount of 5w would have broke loose any of this sludge.

I bought a S10 truck, 4cyl, 79,000 miles, from an older guy, that the engine had seized up. I removed the oil plug, but no oil came out. After removing the engine, I pulled the oil pan, and over 7 qts of oil came out. The screen on the oil pump was completly cover, starving the engine of oil. Talked to the older guy, he had used nothing but 30W oil from the time the truck was new..

My theory is that thin oil, 5W, will not remove any sludge, and 30W will only add to a bad situation. Everyone to their own opinion.....

[Young Ed]

I have had a couple negative expierences with 30W oil.

After coming home from Vietnam, 1970, I bought a 1966 Plymouth from my Aunt, 40,000 miles on it.

The car had nothing but 30W Quaker State oil, at 3000 miles changes.

At 42,000 miles, I was changing the oil, and new valve cover gaskets.

Under the valve covers was so much almost dry sludge, I could barely see

the valve springs. I dropped the oil pan, and the same situation was there. The screen on the oil pump was in very bad shape. No amount of 5w would have broke loose any of this sludge.

I bought a S10 truck, 4cyl, 79,000 miles, from an older guy, that the engine had seized up. I removed the oil plug, but no oil came out. After removing the engine, I pulled the oil pan, and over 7 qts of oil came out. The screen on the oil pump was completly cover, starving the engine of oil. Talked to the older guy, he had used nothing but 30W oil from the time the truck was new..

My theory is that thin oil, 5W, will not remove any sludge, and 30W will only add to a bad situation. Everyone to their own opinion.....

I've heard way back that Quaker state was known for this. Its at least possible with the 66 plymouth that it was the brand rather than the weight of oil. Its also hard to know how well these people took care of their cars. If the cars only had short to the grocery store type drives the engines wouldn't get warmed up enough and a 3K mile change interval wouldn't be frequent enough.

[james curl]

We gave my mom my 64 Olds cutlass to drive after we got married. She drove it to work, church and to the store. She worked less than 2 miles from the house and every thing else was within one mile of home. The first year she drove less than 4500 miles, she retired after that and only drove to church and the grocery store, about 400 miles a year. She thought that she did not need to change the oil until she had 2000 miles on it. When I gave her the car I told her I always changed oil and filter every 1200 to 2000 miles so that was what she was doing.

[Don Coatney]

I have had a couple negative expierences with 30W oil.

Everyone to their own opinion.....

I suspect that leaded gas may have had as much (if not more) to do with the sludge as the 30wt oil. That plus driving the car on short trips never allowing the engine to come up to full operating temperature.

[JIPJOBXX]

Interesting article and so true! I know at Wallmart they want you to come back at 3,000 miles and my manufactures manual call for an oil change at 5,000 miles.

http://www.edmunds.com/car-care/stop-changing-your-oil.html?mktcat=maintenance-article&kw=stop+changing+your+oil&mktid=ob61762858&msite=w

[TodFitch]

I suspect that leaded gas may have had as much (if not more) to do with the sludge as the 30wt oil. That plus driving the car on short trips never allowing the engine to come up to full operating temperature.

Seems very reasonable to me that short trips and leaded gas are culprits. If they were cheap on the oil and got non-detergent that could be another factor. The weight/viscosity of the oil itself should not, as I understand things, have made that much difference with respect to sludge build up.

[meadowbrook]

Hey guys, you can have straight weight oil or multiviscosity oil that is detergent oil. There is no connection between the oil's weight and whether it has detergents.

The only non-detergent oil I have ever found, though, is straight 30 and straight 10, I have never seen multivis oil in non detergent form.

The subject of whether one can use a detergent oil in an old engine from the 50's safely is well worn in this forum. I have a 50 Dodge and have used non detergent 30 weight from NAPA (Valvoline) and Kendall since I got the car in the last 2 years, however, I am now thinking it may have seen detergent oil before because who knows if the previous owner even know about non deterget oils.

I also removed the oil pan to replace the gasket and saw little sludge there, though the valve area on the side on the engine is pretty caked.

The only issue I have with detergent oils is that they keep the dirt in suspension so the filter can get it out (assuming you have a FULL flow filter), so an engine without this may not benefit from a detergent oil.

But that's theory. You will hear different opinions and experiences. Like old VW air cooled engines have never had oil filters and they have been happily running all through the 50's 60's 70's 80's 90's up to 2004 when the last Mexican one was made, on detergent oils and they tend to last long.

[speedyshark]

Wow lots of different opinions, but that is what makes the mopar world go around. guess I will try a good quality 30w oil and go from there.

Thanks to everyone who has chimed in, I did learn some good things.

[Robert Horne]

I suspect that leaded gas may have had as much (if not more) to do with the sludge as the 30wt oil. That plus driving the car on short trips never allowing the engine to come up to full operating temperature.

Probably true about the gas back in the 70s. My Aunt bought the 66 new for around $2300, put 10,000 miles per year, about average back then.

At the same time, 1970s, my brother in law worked at the police garage.

He showed me the police car engines with over 300,000 miles on them, in for a rebuild, with no sludge at all.

[Rusty O'Toole]

A lot of uninformed people think all old cars need straight non detergent oil. Not true. Detergent oil has been on the market since the 40s and multigrade since 1951. If your car was made after 1950, or even before, chances are it always had detergent 10W30 oil.

Under "Engine Oil Recommendations" the 1951 owner's manual says "Custom in the past was to use heavier oil than at present. The use of light oil is an aid to cold weather starting, fuel economy and the proper lubrication of parts.

The selection of the proper brand of oil should be based on the reputation of the refiner or marketer."

They go on to say that you should change your oil every 1000 miles in winter, 2000 miles in summer unless you have a Chrysler with the full flow filter. In that case, change your oil every 5000 miles.

Change filter every 8000 miles, every 5000 on Chryslers.

When driving in dusty conditions cold weather or short trips change oil more frequently.