Let’s Talk Motor Oil, Part 2

I just wanted to first begin with saying “thank you” for all of your nice comments on my recent posts. Remember my mission is to first teach you something about cars and secondly to entertain you. I love cars and car care! All right, enough of that. Let’s get busy and continue with our talk about motor oil specifications and ratings.

If I haven’t said this once, I’ll say it another dozen times, read your owner’s manual and see what your car’s manufacturer recommends for its oil. We already talked about it’s viscosity requirements, but what else is important? If it calls for synthetic oil, you must stick with it. Remember motors are often  designed with a specific type of oil flowing through it. These oil requirements are called OEM (Original Equipment Manufacturer) approval ratings.

Let’s take my 2006 Corvette for example. GM calls for a synthetic 5W30 (Mobil 1 is the factory fill). Other 5W30 synthetic oils are acceptable but they must have GM specification 4718M and GM6094M. These are OEM  requirements for high performance/high heat temperature performance required by General Motors engineers. My Jeep SRT-8 and its Hemi require 0W40 or 5W40 that has the MB 229.51 specification. So the point here is that more than the viscosity and type of oil is important to your vehicles engine. Volkswagen, BMW, and Honda are a few other carmakers that have an OEM requirement for the engine oil.

There is a lot of other info on the back of oil bottles. There is the API rating or the American Petroleum Institute classification system. The letter “S” followed by another letter, currently “SM” for example, denotes any oil appropriate for gasoline engines. SM oils are superior to the older SL oils. SM ratings emerged in late 2004. So if you have a 2001 car it likely called for SL oil. SM oils supercede SL oils and will cover you just fine. Without getting off topic, one of the changes in the newer SM rated oil was an agreement to decrease a zinc additive used for decreasing wear called ZDDP. Car manufacturers were concerned about burning of SL rated oils and zinc poisoning the pollution devices (mainly the catalytic converters). This would lead to an increase in air pollution. We’ll talk another time on ZDDP lower levels in SM oils and a problem with older designed engines later in another post.

Okay, so where are we? The API with the letter “C” is for diesel engines and yes there are diesel manufacturer requirements too. Currently CI-4 is the newest for diesel oils. You may notice that some oils will have both an “S” and a “C” rating for example an API Sm/CF rating. So yes some oils can be used in different types of engines, both gas and diesel.

But wait…there’s more! Many oils have a European rating as well. ACEA is the abbreviation and it stands for Association des Constructeurs Europeens d’Automobiles. Yikes! ACEA has established four performance categories. Category A is for petrol (gasoline) engines and Category B for diesel motors. There’s also a C and E category but they are for newer diesel engines. We’ll keep our discussion to the A and B categories.

An ACEA rating of A1 or A2 is for base performance levels, A1 for lower viscosity fuel-efficient oils and A2 for higher viscosity oils. A3 and A5 are higher performing oils where A5 is for high performance lower viscosity fuel-efficient oils. A4 is for direct injection engines like those found in the engine bays of Audi cars. The B category for diesel motors is similarly divided where B5 is king.

Lastly, there is an ILSAC rating which is the International Lubricant Standardization Advisory Committee. They place a GF rating on an oil if it proves to be energy conserving. The latest GF rating is GF-4. It provides better fuel mileage that the older (prior to 2004) GF-3.

So have you had enough? Bet you won’t look the same way at a bottle of motor oil ever again! Think about how much you have learned! “So Uncle Vinny, does that mean that the best oil has an API seal of approval, with SM, A5 GF-4 rating?” Well maybe not or at least not so fast. There are these things called boutique oils that build oils the way they believe they should be made. And they don’t pay the high fees to have their oils API certified. There are oil cults out there! And there’s more to the story. We’ll continue onward with part 3 about synthetic and conventional oils.

Thanks for stoppin’ by!

Stay safe out there!

Uncle Vinny