What kind of oil should I use?
My recommendation is to use a 5W-30 or 10W-30 API rated SJ -CF oil if your car doesn't use any oil between oil changes. If it has a lot of miles on it (100,000+) or it has started to use oil, use a straight 30 weight SJ-CF oil.
Let me first attempt to explain the alphabet soup that is commonly used to describe different oils. As an example, let's determine what kind of oil a 5W-30 SJ-CF oil is.
The API rating of an oil is actually a translation of the technical jargon of the American Society of Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE). The SAE rating reflects how the oil will flow at particular temperature. A 5W-30 protects like a 5 weight oil when cold and protects like a 30 weight oil when hot. A straight 30 weight oil is not supposed to change viscosity so it will protect and flow like a 30 weight cold or hot. With the test results from the ASTM and the SAE rating, the API then rates the oil.
If the API rating (SJ-CF) starts with an "S" that means the oil is rated for a gasoline engine. SA, SB, SC, SD ratings are obsolete. The only current ratings are SG, SH and SJ with SG being the lowest rating and SJ being the highest. The API rating may have a dash then a CA, CB, CC, CD or a CF rating which gives the oil a diesel engine rating. Again, CA is the lowest rating, CF is the highest.
We expect that the next API change will move the gasoline rating SJ one step higher to an SK. The test the oil must pass will change and become tougher so the rating will go up one letter to reflect that. The highest rating today for a diesel oil, a "CF", is expected to stay the same for awhile.
By the way, the "W" in the SAE rating (5W-30) doesn't mean weight like most people think. It means winter.
If you drive your car hard and you are in the city 95% of your time, then you can use either a 5-30 or 10-30 SH or SJ oil. We should use an oil that protects us between the temperature range we live in. Using a 5W-30 or 10W-30 oil will generally give you 1-3% better gas mileage than a 30 weight or 20-50 weight oil. Thinner is better, both for your engine and your pocketbook.
I know that putting a thinner oil in your car goes against everything you have been taught. Most of us cringe at the thought of putting a 5W-30 in our engine. First, you must understand what motor oil is supposed to do.
1. Oil is used to provide lubrication between two moving parts to reduce wear. Most internal engine tolerances are measured in thousands of an inch and many tolerances are no thicker than a human hair. So, if you wanted to fill an opening with oil that was no thicker than a human hair, which would do a better job, peanut butter or sewing machine oil?
2. Oil is used to gather or absorb heat from the internal engine parts and carry it away. Let's say two pieces of metal are rubbing against one another at say...50 times a second or 60 MPH. If we want to flush this joint with oil and keep a continuous stream of oil running through and over it to gather the heat generated and carry it away, would you use peanut butter or sewing machine oil?
3. Oil is also used to flush the metal particles from the bearings of your engine. This one should be easy...peanut butter or sewing machine oil?
4. 90-95% of all mechanical engine wear occurs in the first 10 seconds of a cold engine start up. That initial cold start wear can equal hundreds of miles of warm engine wear.
So.... you it's your choice, peanut butter or sewing machine oil?
There are situations that call for a thicker oil. In the event your car consumes an abnormal amount of oil between oil changes, using a thicker oil would be beneficial to you. A thicker oil would, in this case, help you control the oil consumption. An abnormal amount is generally described as more than 1 quart every 1000 miles or so.
But keep in mind that every car made in 1993 and newer recommends a 5W-30 or a 10W-30. We must work to overcome the idea that thicker is better unless of course there is a reason.
I hope by now you are convinced that peanut butter type oils no longer belong inside your engine. We now know thinner is better.
My personal recommendation for the brand of oil to use is Valvoline. I have found over the years that my engines last longer and are cleaner inside than many of my customer's cars we take apart. This could also be attributed to my good maintenance habits.
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