If you don’t change your oil your engine will fail, we all know this. Over time your oil starts to break down, become over contaminated, and cause severe engine wear. Allowed to continue unchecked you will start to open up critical clearances in your engine that rob you of horsepower and fuel mileage. It may start to rear its ugly head by showing some smoke out of your tailpipe… or maybe your engine start to run a little rough… the fact is once you get to this point it is too late. You can never recover the power and performance you had before the excessive wear took place.
So how long should you go before you change your oil and What is a good motor oil and what should you look for? I am going to cover a couple of the most important qualities of a motor oils to help you understand what you should be looking for when you buy and change your oil.
It is amazing to imagine the speed at which machinery is whirring along inside an engine. When you are cruising with your engine at 1800 rpm the crank is rotating 30 times every second! In a 4 cylinder engine each cylinder is firing 15 times a second. Can you imagine 15 explosions in each cylinder every second… pretty amazing.
Now each of these little explosions creates exhaust gas which is acidic. If you have ever seen what a little acid will do to steel overtime then you are right to be concerned! Acid will literally eat through steel if you give it a chance. The combustion in your engine makes acids that want to chew their way from the inside of your engine out. So how do we protect our engines from this raging inferno of hot aggressive exhaust gas…
That is where an oil property called TBN comes into play… that is the total base number. If you remember your chemistry basics then you might guess “total base number” is a reference to the alkalinity of the oil. TBN is an indicator of a motor oils ability to neutralize the environment inside the engine. The higher the TBN number the better chance it has at keeping your engine from rusting on the inside for longer. This helps keep your engine clean and “peppy” with good horsepower output and gas mileage.
Keeping the corrosion potential in the engine down is extremely important but oil is like a chain as it is only as strong as its weakest link. Sure we want a strong TBN number so the oil protects the engine a long time but what is the point if the engine is rubbing itself to death anyhow. What I mean is if the oil does not have the capability of preventing friction damage and metal to metal contact then it doesn’t matter how high the TBN number is… you have a wear problem anyway.
There is a test called the 4 ball wear test that is indicative of an oils capability of protecting lubricated parts. The very purpose of using oil is to protect the engine from damaging itself from friction. Without oil you would litterally weld your cylinders to the cylinder walls if you didn’t throw a piston rod first. The 4 ball wear test on an oil can give you sense of what your oil is capable (or not capable) of.
If you can imagine four metal balls (from a ball bearing say) stacked with three on the bottom in a triangle pattern and one on the top you can visualize a little pyramid of balls. The test holds the bottom three balls in that pattern and forces the top ball down into the base of the pyramid. This is done with the top ball spinning and all 4 balls submerged in an oil bath. At the end of the procedure they inspect the balls for wear scars located at the points of contact and they measure the size of the damage. Some oils don’t fare so well and others really stand out.
There you have it… make sure you have a strong TBN number oil and check the 4 ball wear test data to confirm your oil is in at least the top half of the performers… and don’t waste your money on anything less.
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