I have seen a couple of threads about running diesel oil as it has more anti-wear additives. I tried it and had a rod bearing knock in 50 miles in my flathead. Yes, diesel oil has more wear additives, but it also has much more detergent for the soot in diesel engines. I saw a couple of articles about this since my mistake. https://bangshift.com/bangshift1320...-what-you-shouldnt-be-running-in-your-engine/
I've always wondered why some people insist on using a product recommended for uses it was not designed for. Perhaps the panache of diesels, you know, those broad-shouldered semi-trucks pulling incredible loads through the Rockies, driven by brawny, ruggedly handsome teamsters?
You can find oil for classic cars all over the place now a days so why use diesel oil in your vintage motor.
If your flathead developed a rod knock in it's first 50 miles after a rebuild, that probably has nothing to do with the oil, and is much, much, much more likely due to incorrect machining, contamination, defective parts, or something else a human did wrong. In other words, prove it - show me root cause. Yes, Diesel Oil has about twice the amount of detergent additives as gasoline engine oil, and generally speaking the same levels of wear preventatives like ZDDP and phosphorus. It has also been proven that those extra detergents do negatively effect how the wear preventatives work and interact, specifically causing an increase in cam wear, especially in flat tappet applications. But, our love of over carbureted antique engines with large duration bump sticks and inefficient combustion chambers (flathead guys - stand up) causes our engines to produce much more soot and sludge than a modern direct injection gasoline engine. For this reason I would argue that running diesel engine oil in our antiquated junk is not nearly as detrimental as it would be in your wife's 2024 2.0L something or the other. At the end of the day, just use the right oil.
> >Oh boy, is it that time again?> > Apparently. Time for bulk sales on STP motor honey. Half 50W diesel and half STP honey should silence that annoying rod knock pronto. View attachment 6368808 View attachment 6368808
Diesel oil was what guys ran to when a lot of newer oil became lacking in zinc. But diesels also got catalytic converters so they eliminated the zinc from diesel oil also. Why people don't just buy oils designed for older engines instead is beyond me. Oil is cheap, and rebuilds aren't. Plus they take time I don't want to spend doing them.
I haven’t seen any oil designed for older engines in my area. There’s a few choices for higher mileage engines but nothing else.
Some clarification - when I bought the car the previous owner said he probably drove it about 5,000 miles over several years. When he purchased the engine he took the pan and intake off and said he said it looked like it had been rebuilt. I drove it a couple of hundred miles and changed from the 50wt that was in it to 15/40 Rotella. After 50 miles it had a knock. Looking over the engine after it was apart everything was great except one rod. The previous owner was quite surprised at what happened and offered to help me out. A friend sent me a link later to a article about why diesel is not a good idea so I have continued to look for information and found the video to quite informative. This is only my experience, and I suggest watching the video I included in the first post for the scientific explanation. Full floating rod bearings. Delaminated on the crank side and worn on the rod side. Measurements are the bearing
I wonder if the 50wt that was in it previously contributed to the rod bearing demise? it's hard to get that stuff moving when it's cold....
The 50wt kept it quiet? Fixing to dig into one that’s had 15/40 diesel oil since we built it. Not for repairs, changing up some things for its new home. I’ll check cam lobes. Probably 35- 40k miles on the build.
You didn't say if you were running any kind of filter. Detergent oils need a filter to remove soot. Non detergent oils led it settle as sludge in your pan
That video spent most the time explaining different kinds of fuel injection, and then goes on to explain how you shouldn’t run diesel oil in a direct injection engine, which almost no one does, because near zero have flat tappet camshafts. Clickbait bullshit trying to contradict what we have all seen work just fine in older carbureted engines with our own two eyes. Diesel oil did not destroy your engine in 50 miles. In many cases you could make it those 50 miles with no oil at all; another thing I have seen with my own two eyes.
I would not run 50wt, but the Ford books indicted it over 90 degrees, 40 wt between 32 and 90 degrees. The car came from SoCal where freezing is not too common. I am not telling anyone what to do. Watch the video and decide for yourself. https://bangshift.com/bangshift1320...-what-you-shouldnt-be-running-in-your-engine/
I literally LOL’ed at comp cams claim they could reliably measure camshaft wear to the Millionth of an inch, and guess what? The best they could say is that is cost .000002” of wear. So they will invest in multi-multi million dollar equipment that is supposedly a hundred times more accurate than they need, pay to properly maintain it in a clean room, but they wont warranty a $20 lifter that is lazy out of the box? There are no variables listed about room temperature, humidity, time in the fixture, etc. all which affect the parts dimensionally well before you get anywhere near millionths of an inch. The suggestion that the oil will blow out a piston in a street driven flat tappet engine is straight up trolling. Is diesel oil better than regular conventional oil? Maybe, maybe not. But it is not going to blow up your pistons, FFS.
> >Clickbait bullshit> >Diesel oil did not destroy your engine in 50 miles.> > Agreed. Oil nerd talks funny. Much more likely a coincidence than the cause.
I’ve heard of Lucas oil being advertised in a lot of old car blogs. I like to buy consumables like oil off a shelf but I guess that’s another thing I’ll have to have delivered.
I got the 30w non detergent speech from my grand daddy and my dad saying if you don’t know what was in it use this and you will not have any problems, and the 20-50 Castrol is what my buddy and I have been using in all of our motors since high school. So I guess it’s just habit but never once have I ever had any issues because of the oil.
I was taught non detergent for engines without oil filters Could flip a coin for the bypass ones. but keeping oil in it and changing regularly has to happen either way
I have oiled up my bodybuilder girl friend with diesel oil, she never spun a bearing or failed a lifter. Case closed.
There is a product in a yellow bottle available at auto parts stores that is basically an additive that makes regular oil of your choice viscosity into classic car oil by adding back the additives that have been subtracted for new cars. Gives an extra 1,200 ppm of zinc and some other stuff…. I forget the name or brand but it works good.
Should I explain again, that the most popular midrange diesel engine in the country still uses a flat tappet camshaft and modern diesel engine oils still have to support this camshaft and lifter design?
I put rotella in my O/T (but still almost as old as the average HAMBer) pickup because I had it; another O/T truck is diesel. I don’t always use it, because I don’t really care as long as it has oil. I drove it 750+ miles yesterday. No flattened cam, no blown out pistons… Even despite the piss that they sell as gasoline out in the middle of the desert. A lot of the car content on YouTube is made for people who aren’t really that into cars… It goes along with all of the stuff we read on the internet about how this/that will never work (like reusing pistons, lifters, etc) despite it being done frequently before the internet. Just imagine how boring this hobby would be if random people on the internet who don’t actually build cars were setting the “standards” for people the who did in the 1950’s like is done today.
The Jalopy Journal
