But there's no way you should be using anything other than full synthetic oil by now. WalMart always has it for around $22 for a five quart container and the difference is huge. It does not break down chemically meaning you can run it for 6000 miles or until it gets so dirty you can't stand looking at it. Full synthetic never freezes or gums up on super cold days.
The cars of 1955 weren't going to live beyond 100K miles anyhow so it didn't matter much but todays cars can live for several hundred thousand miles IF you don't destroy them by running cheap oil in them.
That's cheap for synthetic, what brand?
FORD recommends 5000 miles with our new Fusion. I have an ‘02 Explorer with 175K on it, and have always changed at 5K. About every other oil change, I top off the crankcase with 1/2 can of STP. At 175K it still doesn’t use a drop of oil.
I use a semi synthetic and change at 5,000-6,000. a 20 percent synthetic blend is cheaper than full synthetic and provides 90 percent of the protection.
Yup. I run Mobile 1 now and it’s $21 for 5. I’m running past 8K on mine current one and it’s a moderate brown. I also flush it every time I change. I’m spending less now in oil changes per year as a result and only have to do it about twice a year instead of 4 or 5 times.
We bought a 1990 Mazda 626 new. At 300K+ I burned a valve at a time when I had neither the time to repair it myself nor money to pay someone to do it. I drove it until it would not make it up the mountain on 3 cylinders. At 359K miles, when I finally pulled the head you could still see the hone marks on the three good cylinders. #4 was worn out from unburned gas (no compression, no burning) washing the oil off the cylinder walls.
We put a junkyard engine in it (~105K miles) and were aiming for 500K on the car when someone pulled out in front of me & it totaled the car at 426K miles.
The whole time we used Walmart brand oil, average change interval was 5000 miles.
(We have had 6 cars go over 200K miles. 3 Mazdas, 2 Subarus, one Mitsubishi. All used Walmart brand oil.)