Selection of the right oil for Flat Tappet engines

I originally wrote this article on oil selection for the Corvair clubs, but it has been suggested that I post it here as well.

There is a lot of good information and a lot of old wives tales circulating concerning oils and older engines. I hope this helps clear up some of it.

Comments and questions are welcome. I'll try to clear up anything I can.

Selection of the right oil for flat tappet engines

Richard, my head is spinning after all that. How can someone go to the parts house and choose an oil if they can't get the Material Data Safety Sheets? I read that you don't want to recommend any particular oil but if I read right, basically any class two base ( that which reads "severely refined" on the label) is okay for the older flat tappet cars as long as it is changed every 3,000 and within the 5-40 weight viscosity range?

Wow I kinda eyeballed that....wish I HAD the spare time to read that! Amazing that there's that much to it!

I think I'm just gonna keep on doing what I do now...I go to wal-mart and get this off-brand stuff. $1.24/qt. Detergent 15w-40, says on it "for 1988 and earlier vehicles" and the rating is CI I think, and SJ. It mentions anti-friction additives "for older engines".

It gets kinda dark after about 200 miles. So that's how often I change it. The '38 doesn't have an oil filter but I dont know if that makes 200 miles about right or not. All I know is an oil change costs me a hair over $8 and without a filter it's even easier to perform, so every 200 miles? Fine with me. I LOVE seeing clean oil and HATE seeing dirty oil.

As I have posted before, Mobil 5000 mile oil is still rated back to SG.

Oh wow! Well somehow I must have missed when you mentioned it previously, thanks for mentioning that!

Will definitely read that later. I have been using Castrol GTX (not the stuff for older engines) 10w-30 for the last several years on my remanufactured 390 with flat tappet hydraulic cam. No problems experienced. I change the oil each spring and fall. Maybe put 2000 miles on the car per year.

Here is an updated link that will pass you first to a page where I'll highlight additions as I update it.

You make a good point that I will clear up a little more in reading the label and seeing "for older cars" or older API specs. That is NOT good. SG is way inferior and has less additive in it than we need for maximum protection.

Of course if you are changing oil every 200 miles, it doesn't matter as much, but the newer oils are so much better in anti-foam and anti-wear, not to mention cleanliness of internal parts. With no filter you need the dispersant to keep the particles from settling out and sticking to parts instead of coming out with the oil.

Selection of the Right Motor oil for Flat Tappet Engines

Hi well I though I could get some info but with 31 pages I got over whelmed as I always use any oil that is on sale like a 10./30 or a 10 /40 . But with this old 1928 Reo what would be the best detergent or non detergent . Straight weight or the multi grade like 10 / 40 ?? I do remember when working stations it took for ever to pour 10/40 in the winter compared to a straight weight . So can this be made simple or at least lee than 31 pages ?? What I would always do is just go and but a non detergent straight weight . before trying to start I plan on pulling the pan to clean as it has been sitting more than 21 years . Mike

You are much better off cleaning up all you can manually and then adding a good CI-4. Not a CJ-4. I would start with a 15W-40, as 10W-40 will shear down (and you probably won't find it in a CI-4). The CI-4 will slowly clean up the inside of the engine. If it gets thick, change it. After about 3 changes (and some miles) it should be reasonably clean and able to get good compression unless there is corrosion in the cylinders or other problems.

Hopefully you don't find problems like I found in my Corvair.

Don't go by the old wives' tale and put non-detergent oil or straight 40 in it.

When I started on that paper my intention was 10 pages or less. It ended up at 16 for the first draft, and then doubled from questions that were of enough interest to be added.

Richard, fantastic paper. I actually found it interesting and informative. What do you think of my Dodge/Cummins diesel reccomendation of 15,000 miles between changes for "normal" driving........Bob

Check this for info on ZDDP additives and more.

http://www.zddplus.com/

15,000 might be a good number if it is highway driving and a good sized sump. Only used oil analysis tells you for sure.

Having realized that I hadn't updated my oil paper in about 2 years, and that people are still downloading it 11,000 times a month (between the English and Spanish versions), I decided to review it and update it.

The English version is up, so you can click on the link and on over to the new version.

For the ones here that may question the ZDDP in modern motor oils (CJ-4), here is a recent analysis of a sample I sent in. Probably more ZDDP after almost 5,000 miles than was in oil in the '60's or '70's.

E64221.pdf

Yep, that is a fairly typical result for that oil, although as they mention, you need to do something about the fuel contamination. Could be as simple as too much idling at startup, or worn injectors. That Engine pushes fuel into those injectors at about 20,000 psi if the HPOP is working properly. Injector clearances are something like 2 microns. any dirt that gets past the filters scratches the HPOP to produce less pressure (less pulverization of the fuel in the cylinders) or scratches the injector nozzles on the way in.

i have the 2003 version in my F550. If you do any driving off pavement, do yourself a favor and put a small filter on the vent valves on top of the fuel tanks. For every gallon of fuel you use, you suck in a gallon of dust filled air. And Ford thinks this is ok. After replacing two HPOP's and 8 injectors, I disagree.

Already taken care of the fuel problem. It seems one of my friends had turned my programmer wide open and the truck was seriously over fueling. Just got a new sample back, <1% fuel dilution, probably most of that was in the almost gallon of oil that stays in the engine when the oil is changed