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What's the Difference in Car Oils and What's the Best Oil to Put in Your Car?

Author:

Dan has been an auto mechanic, truck driver, engineer, and many other things.

What Is Oil and Why Is It in My Engine?

Oil is the substance that lubricates the internal moving components of your vehicle's engine. There are many different types of oils on the market suitable for car engines but there are some basics that you should know when purchasing an oil.

Viscosity

This is simply how readily the oil flows. A higher-viscosity oil will withstand more heat than a lower-viscosity oil. However, at colder temperatures, it can actually become so thick that your starter cannot turn over the engine—and worse yet, it won't flow to all the moving parts it should. A viscosity that is too low won't maintain a lubricating film on engine parts, allowing them to make metal-to-metal contact. Either extreme is very bad!

Single-Grade Versus Multi-Grade

Single-grade engine oils (such as SAE 30) used to be the standard for engines operating at high temperatures (such as air-cooled engines). Since the advent of the American Petroleum Institute (API) rating system, the multi-grade oils that proliferate on shelves nowadays are suitable for nearly all applications. I did have an older gentleman tell me today that his '30ish Ford won't build oil pressure with multi-grade oil—but then again, I'd be surprised if his '30ish Ford builds oil pressure at all.

Coincidentally, SAE stands for Society of Automotive Engineers.

Selecting Your Grade

So, which oil you should choose will mostly depend on what you're driving. If your car is not an antique or air-cooled, the safest bet is to use a multi-grade oil. The first number on a multi-grade oil indicates the "cold" viscosity of the lubricant, and the second number the "hot" viscosity. For example, a SAE 10W-40 motor oil would have a viscosity rating of 10 at 0-degrees Fahrenheit (the W indicates "Winter") and a 40 rating at its maximum recommended temperature (not engine operating temperature—ambient air temperature).

The following chart is a good place to start. Determine the temperatures you'll be driving in and select an oil accordingly.

The Breakdown

Multi-Grade Oil Viscosity Chart

Multi-Grade Oil Viscosity Chart

Special Considerations: Driving Conditions, the Age of Your Car, Winter Weather

Also, consider your driving habits and the condition of your car. If you drive hard—keeping the engine near redline for extended periods, or you do a lot of high RPM "freeway" driving—then you may want to select a higher-viscosity oil for your car. Also, if your engine is high mileage, a high-viscosity oil will keep it a little quieter and may not slip through the rings to be burned (blue smoke).

If your car is newer, you will most likely want a lower-viscosity oil. This is true of most newer high-performance cars also—they too have tighter bearing tolerances and recommend a low-viscosity oil (it doesn't rob as much power from the engine).

Overall, If you expect very cold weather ahead, definitely choose an oil with a lower "cold" viscosity. If you live in a warmer region, a higher winter rating (the W rating) will help keep your cam and valves from clattering when you first start your car.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Comments

WCarp on June 20, 2013:

Concerning dlarson's response above, there must have been another factor or factors related to the pickup engine only lasting 120,000 miles. I have had a fair amount of experience with Amsoil over the years and even when used in an 80 Ford Fairmont that had a problem with gas washing down the cylinder walls, in heat soak conditions, it lasted approximately 180,000 miles.

μεταχειρισμενα αυτοκινητα on July 10, 2011:

i just got my first car, although it was a used car (?????????????? ??????????)it still work good.I don't have enough ideas about cars . i just find your hub interesting .There's are many thing i want to know about cars and i hope you can write more details.

yaseen hookpra on December 15, 2010:

Thanks for this great overview of the different roles of the automobile in our lives, and thanks for answering my request!

wineandcars from USA on January 26, 2010:

Vintage cars are the cars that are dreamed by the entire world and are sharing the highest popularity after the Limousine cars. They are the master pieces of creation of older times.

Novak on January 18, 2010:

Great information. With so many options out there, it's tough to decide which would be best for your vehicle, depending on its age and condition.

Shannon Paulk on January 08, 2010:

Very informational hub. What type of oil to put in your car is a common concern for auto drivers. Thanks.

Get Free Visitors on December 08, 2009:

charmful

Jason from Belding, MI on January 23, 2009:

I do know Mobil makes synthetics for a lot of companies and that Castrol Syntec is not a full synthetic as they claim (at least in not the Americas) I have had good luck with synthetics, but as was mentioned, FILTRATION! I never skimp while buying the filter. I almost lost a freshly rebuilt engine because of a faulty cheap Fram filter.

Dan (author) from Priest River, ID on May 13, 2008:

Ah yes, the synthetic vs. mined petroleum debate! :)

My father was an AmsOil dealer when I was in high school. The truck that he gave my brother and I was fitted with an accessory AmsOil filter (in addition to the regular oil filter) and was lubed entirely by AmsOil synthetic oil. It was a 1982 Chevrolet 1500 shortbed fleetside 2wd pickup and it died promptly at 120,000 miles. The synthetic lubricants and extra filter did not save the engine from its typical lifespan.

The truck died while we were in college and at the time we were working in the college (University really) motor pool. I asked my boss (who was a certified mechanic) "why didn't the engine last longer on synthetics"? His answer to me; "its not the lubrication that kills the engine, its the dirt." Even with the extra filters, to keep an engine clean requires changing the oil.

Now in our '82, the extra filter stretched the synthetic oil changes to 7500+ miles AND a normal oil would be broken down after this much life in a vehicle. Even in the '90's, the cost of the extra filter and synthetic lubes about equaled a typical oil change cost (since I did the work myself).

I am not against synthetics and I don't know the differences between the different synthetic brands. In my limited experience with them, they did not stretch the life of the engine - they simply stretched the life of the oil change but with no overall cost savings. In today's world where conservation is king, that is probably a very good thing to consider. However, if your car leaks or burns oil, then you're burning money on synthetic lubes as well.

Jerry Watson from Hermitage, Tennessee on May 12, 2008:

You didn't touch on the synthetic lubricants in your article and I would be interested to hear what you have to say on the subject. I thought you did a good job with this Hub about oil, though. Pretty slick! (Sorry, couldn't resist!)