[65Stanger]

What weight oil do I use in a 1965 mustang 200 ci? I have the oil I put in after I first installed the new engine in the car, and it's getting to the point now where I have to change the oil. Should I use 10w20 or 10w30? Straight 30w?

[jimfulco]

10w30 (or straight 30 if you don't like multi-grade oil) should do fine. If you use straight 30, be sure it's API service rating (marked on the jug somewhere) is SJ or SL. There are a few places selling "non-detergent" 30 that has a rating of SA or SB, and that stuff's only suitable for making an oil slick. It should NEVER be used in an engine.

[65Stanger]

Thanks man! I live in CA, so I will probably go with straight 30w. I appreciate it. =)

[Max Keith]

I would recommend running 10W30, or even 10W40 during the summertime. I dont recommend running straight 30 as you never know when your weather is going to drop off and get chilly. If you see temps in your area below 30 degress, 30 weight will be rather thick, and will take a long time to warm up and give proper circulation. This equates to short engine life. If you live in an area where you have consistant temps from about 50-80 degrees, you will be fine with the single weight, The reason I do recommend going with 10W40, is that if your engine has some high mileage on it, then the heavier oil will give you a bit better bearing lubrication and its a way of taking up some of those high mileage clearances on bearings, as well as maintaining higher viscosity in hot weather.

[65Stanger]

the engine has about... 1300 miles on it. This is the oil I've been using to break in the engine. The user manual says 10w30, it's a CA car. I think I'll go with that! Thanks guys. =)

[farna]

Jimfulco is mostly correct. Non-detergent oil should only be used in an engine that doesn't have an oil filter. Like a Briggs and Stratton. Detergents trap dirt and other contaminants and keep it suspended in the oil. Sounds bad at first, but oil picks up contaminants after combustion, so mostly when it's draining back to the pan. Then it's sucked up and filtered before going to the bearings. Non-detergent oil lets the trash settle out of the oil to the bottom of the pan. If you ever get to read an old service manual, like prior to the mid 50s, there will be an oil pan removal and cleaning interval. That's why -- you cleaned the sludge out of the pan since there was no filter.

It was pretty common for people to strain the used oil through a few layers of cheese cloth then cover and let sit between changes (or a couple changes). There would be additional sediment at the bottom of the container. So you pour all but the last quart or so back in the engine then topped off with a fresh quart. Through the late 30s there were few, if any, additives in oil. Most of the additive research came about during and right after WWII. Oil never loses is ability to lubricate, it just picks up trash in the engine and the additives wear out. Oil change intervals were a lot lower back then too. A 1941 Chevy truck manual recommends 2,000-3,000 mile change intervals (this using virtually no additive single weight oil -- multi-vis wasn't invented yet). A 1915 Chalmers manual recommends changing every 1,000 miles. The best description of what happens to oil I've read is in a 1925-28 Diana (made in St. Louis, MO) manual! http://www.tocmp.com/manuals/Moon/Di...%20067_jpg.htm.

Read it! That explains why most EFI vehicles recommend 5,000-7,500 mile drain intervals. Not only has oil improved with all the additives used now, but there are fewer, if any, combustion by products and virtually no fuel dilution of the oil in a properly running, good condition EFI engine. But the oil change industry has us all brain washed into the 3,000 mile oil change interval from 1942!! I change mine every 5K, which is what the manufacturer recommends. My Subaru had a 7,500 mile recommended interval, and I changed it every 7K. It was also one of the most reliable cars I've ever had. My ex wife st5ill keeps the 7K (more or less) interval, and still drives the car with close to 200K on it now. It's a 93 model (one of the last 2WD).

[67FordFalcon]

Originally Posted by 65Stanger

What weight oil do I use in a 1965 mustang 200 ci? I have the oil I put in after I first installed the new engine in the car, and it's getting to the point now where I have to change the oil. Should I use 10w20 or 10w30? Straight 30w?

30 in the winter and 20 in the summer