Engine Oil Basics
The internet, the work place, the family garage, and every where I go seems to be the right place for a discussion about motor oil. Everyone knows I’m a gear head, so I get questions from time to time. The problem is, if you ask a Gear Head a technical question, you could be there a while. And if you get two Gear Heads involved… well, you might as well pack a lunch and make a day out of it.
By doing a web search, you’ll find tons of information about oil. Some of it factual, some of it hear say, and some just advertising hype. When looking at the web site and the data the first thing to ask is, “what is the source?” If they’re trying to sell you something, you should be immediately suspect. Pretty much the same with anything else, I guess.
www.BobIsTheOilGuy.com is a good source, but it often takes some digging to find an accurate answer.
I am not a tribologist, and don’t claim to be. But I am an Old Guy. Over the many years, I have read a lot about motor oil from a lot of sources. And I have some limited experience that I try to pass on. I’m just an average Gear Head, without a big budget for testing and research. Don’t have that kind of time, either. But, there are a few good sites on the interweb that do have that kind of information. Duck-Duck-Go is your friend – but only if you have plenty of time.
Synthetic vs. Dino
This is always the number one question I see and hear. Which is better? To which I respond, “For what?” Oil is a tool, designed to perform a function. Like tires. You can’t decide on the proper tool until you define the function. It’s like asking, “I have to fix my car, which wrench should I use?”
Synthetic oil has a couple of small advantages. It can handle more heat for longer periods before breaking down or vaporizing. But the differences can be pretty small. And the only time that really matters is true severe duty – pulling a trailer through the desert, road racing, etc. RPM’s heat oil like nobody’s business.
Most auto hobbyists will never see the kind of abuse that needs that extra bit of heat resistance. Heck, my car rarely see’s those kinds of engine oil temperatures.
The other advantage is extended drain intervals. For a race/track car, not a big deal. For most hobby cars, not a big deal, either. For example, most Cobras rarely see more than 5,000 miles per year. But if you put 15K mile a year on your DD, it might be more convenient to change the oil every spring, instead of every 4 months.
Synthetics do tend to pour better at extremely low temps. If you live in the frozen north, a true synthetic will circulate through the engine a lot faster on those cold morning start ups.
The down side of synthetic oil is the cost. Expect to spend about 30-45% more for the synthetic. But if it lasts twice as long, you’ll save money in the long run.
More power with synthetic? Maybe. But it’s not that much, certainly less than 4-5 hp at the top end. Not enough to base a decision on for most of us.
What is a synthetic?
Ah, now that is the question, isn’t it? Lots of oils claim to be synthetic, but are they really?
A synthetic is just that – synthetic. Man made. Fabricated. Artificial. Not from natural sources. Expensive.
However, the legal and marketing definition is a little different. If a motor oil can be refined enough to meet certain performance standards, and contain at least some synthetic components, it can be labeled, “Synthetic”. And who made those standards? Why, the oil industry of course. In other words, “It’s a synthetic oil because we say it is“.
Good enough for the FTC; not good enough for me.
As you know, base stocks are labeled I-V. Group I and V are rarely used in a motor oil. Group II and III are the most common base stocks, and come from dead dinos (or wherever) . These are readily available, and relatively inexpensive. Especially with the price of oil currently <$45 a barrel.
Group IV base stocks are truly synthetic, a PAO made in a manufacturing plant through a non-natural process. And this is a key point. If it contains mostly refined petroleum, then it’s not synthetic. Mixing some PAO into a petroleum product does not make it a synthetic.
In a man made PAO base stock, all of the molecules are the same size.
How do you know what your oil is composed of? Well, you can’t ask the manufacturer. They’ll just give you the company line. They might as well read the label off the bottle for you. One of the best ways is to look at Material Safety Data Sheet, now called a “Safety Data Sheet”. It won’t come right out and tell you it’s a PAO. It will say something like “homopolymer”, which tells you that all of the molecules are the same. The higher the percentage, the more PAO base stock it has.
on 4/15/2021, I looked at all of the synthetic oil SDS’s I could find on the web. AFAIK, there is only 1 true synthetic oil on the market today: Red Line. Shocking, isn’t it? Every other one I looked at (Schaeffer, Miller, Amsoil, and Royal Purple) had a small amount of monopolymer.
This is from the SDS for Royal Purple 5W-30 HPS:
Distillates (petroleum), hydrotreated heavy paraffinic ≥50 – ≤75%
Dec-1-ene, homopolymer, hydrogenated Dec-1-ene, oligomers,
hydrogenated ≥10 – ≤25%
Distillates (petroleum), solvent-dewaxed heavy paraffinic ≤10%
Distillates (petroleum), solvent-dewaxed light paraffinic ≤10%
Distillates (petroleum), hydrotreated light paraffinic ≤10%
Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters,
zinc salts ≤3%
Propietary Component ≤2.% SDS-MO-5W30HPS-US-Eng.pdf (industryuptime.com)
Sometimes you can find European motor oils from the same companies (like Castrol) that are true synthetics. But you really have to do your research, shop carefully, and buy and stockpile when you can.
Most motor oils on your local shelves are semi-synthetics; highly refined (hydrocracked) Group II or III dino oils. Some even have a little Group IV PAO mixed in for whatever reason.
What’s Wrong With Semi-Synthetic?
Actually, nothing. Most of them are fine oils, and for the average engine will do perfectly fine. For your daily commuter, do not be afraid to use them if they meet your needs
But, they are not a PAO synthetic, and do not perform like one. If you need that extra bit of performance, make sure you’re getting what you pay for. Redline is about 50% more expensive than Royal Purple, and about twice as expensive as Castrol.
Which Semi-synthetic to use?
Well, that’s another big can of worms. Again, it depends on usage. Different oils will score differently on different tests. Engine wear and TBN numbers – based on UOA’s – are helpful guides. But I think all of the top 4 are about the same.
I tend to use Royal Purple. It’s easy to come by around here; even Wally World carries it. And it’s priced about the same as the others. Miller is the new official oil of NASA for 2016; so NASA members can get a discount. Schaeffer makes a diesel specific oil. Red Line is hard to come by in my neighborhood. And Amsoil has that weird dealer network that makes me think of Tupperware.
For the last 10 years, I’ve been rebuilding my street/race Cobra engine every other year. It’s a 427 cubic inch Dart block Windsor, making a bit over 600 dyno proven horsepower. On the track I beat the crap out of it lap after lap. On the street I love to hear it wind up to 6,500 rpm’s and scream like a banshee. I’m not afraid to run it hard. At each overhaul, I see very little wear. Bearing clearances are still well within specs, and the cylinders walls only need a lite de-glazing for new rings. That’s my anecdotal evidence for using Royal Purple motor oil. And, no they don’t pay me to say that. But they could! RP Guys, call me! 😉 I’ll gladly accept sponsorship.
What is a UOA?
Used Oil Analysis. You can send an oil sample in to a couple of places, and they’ll analyze it for you. It’s a helpful guide to let you know if the oil is performing well, or how long you can run the oil. It’s not the end all – be all, but it’s helpful information. I use Blackstone Labs.
If you look at the top of each column, you’ll see how many miles are on each oil sample. One of those columns says, “2”. After changing the oil I only drove the truck for 2 miles, then drew out a sample. That gives me a base line for comparison. Some people would call that a VOA, or Virgin Oil Analysis.
I’ve tried a lot of oils in a variety of vehicles over the years. Turbocharged and air cooled engines put the greatest strain on engine oil. I used to ride a turbocharged Harley-Davidson Wide Glide; that was a fun bike. Based on the UOA’s, I have found Royal Purple to hold up better than anything else I’ve used.
I could not find a place to get oil analyzed to tell you what it’s made from. Specifically, what base stocks are used. If you know of a place that will do that for a reasonable price, please let me know. BobsExocet@comcast.net
When to Use Dino Oil?
Actually, a lot of people should use dino oil. It does it’s job very nicely, and is inexpensive. It doesn’t last as long, usually about 5,000 miles. Some of the new Dino oils will easily last 7,500 miles! But a lot of hobby cars only get driven <5,000 miles a year. And you should be changing the oil every spring or fall. So dino oil makes a lot of sense. You can spend $20 or $50, and get the exact same results.
I used Valvoline Blue dino oil in my Cummins turbo diesel truck. It easily lasts 14K miles, and is a LOT cheaper than the synthetics. My previous Chevrolet 4 cylinder turbo diesel got Castrol Dexos2 dino oil, and it lasts 7,500 miles in moderate use. Let the UOA be your guide.
I also use dino oil for a new engine break in. I use the cheapest API oil I can find, and run the new engine through a couple of heat cycles; check for leaks, set timing, idle, adjust mixture, etc. Then change oil and filter, using the same inexpensive dino oil. After going through a couple of street heat cycles, I dump that oil again. That’s when I add the good stuff, because I don’t plan on changing it again soon.
Oil Testing Web Sites
If you cruise around the interweb for a short while, you’ll find a number of web sites that will publish various test results. Some of them are worth reading, and some of them are not. As I said before, first look at the source. If they’re trying to sell you something, be immediately suspect of their results. They might be a bit skewed towards their own product.
Second, look at what the results DON’T tell you. For example, this site by 540 Rat is an excellent source of information: https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
This guy spent his own time and money testing a bunch of different oils and additives for PSI wear protection and thermal breakdown. Excellent information. If you’re interested, I highly recommend reading through that page.
But what it does NOT tell you is longevity. How could it? One guy can’t test longevity in a vehicle on the road over 5-10K miles for 40 different oils. An impossible task. Only you can do that in your car.
So, here’s my suggestion:
- read through my page on viscosity, and choose the right viscosity for your use.
- read through this page and choose petroleum, semi-synthetic, or synthetic.
- read through 540Rat’s page, and pick the brand you want.
As you’re changing the oil, collect a sample and send it off for a UOA. In the appropriate time frame, collect a clean sample and send it off for another UOA. Compare the two. Is your new oil doing what you want it to do? Did it last long enough? Can it go longer? Do you need to pick something else?