Motor Oil

I’ve heard it said that “motor oil is motor oil” and that as long as the weights are the same (ie: 10W30) and the API rating is the same is makes no difference what brand one uses. Is this true? Assuming that it is true, is there any reason not to use a brand such as WalMart’s Super Tech oil instead of Pennzoil or Valvoline?

Oh no, here we go again!

My own $.02 is that all equivalent motor oils aren’t necessarily the same-- you can see in various laboratory-type tests that some have better detergents or might be more resistant to viscosity breakdown-- but in real-world practice if you change your oil in timely basis there’s no advantage whatsoever to more expensive oils.

Thanks for your answer, but I just have to ask. Was that comment necessary?

What type of car do you have ?
Honestly, my advice would be that a good way to avoid problems would be to use cheap oil in a cheap car and follow the oil change schedule.
A more expensive or high performance car might be worth the higher expense of a more expensive oil.

It all seems to be a gamble, and there are many different opinions. It just seems to me that your oil gamble should match the value or performance of the car that you are driving.

No snarkyness intended. Motor oil threads tend to get long and inconclusive because (IMHO) it is damn near impossible to come up with any conclusive long term data one way or another on practically any question involving motor oil (brand, synthetic vs. conventional, change interval, etc.) because when you start talking about cars that are run for decades and hundreds of thousands of miles there’s just too many other variables.

As far as general quality level, I don’t have any qualms about house brands. They’re made by major refiners like Pennzoil and Valvoline. Wal-Mart, NAPA, and the like don’t want to sell junk and be on the hook for engine failure any more than Castrol or Kendall do.

There are, however, many possible differences besides viscosity and API rating. For example, many oils that meet the specs for domestic and Asian cars do not meet the specs for European cars. And even though Wal-Mart oil may be made by Pennzoil or Quaker State, it almost certainly has a different formulation than the oils sold under those brand names. Whether the differences significantly affect real-world performance is a much trickier question.

Sometimes an oil will say “suitable for” rather than “approved by” a given vehicle manufacturer. On the reasonable assumption that if the oil met all the manufacturer’s specs it would be thus approved (and bragged about), the logical conclusion is that the oil manufacturer declares it’s okay for those vehicles, but the car manufacturer does not. For a typical American car, I wouldn’t lose sleep over this. For a high end European car I would.

Soon a new certification (ILSAC GF-5) will be available, which will probably add some more confusion to the issue. And the issue is already confused – note this quote: “Motor oils that meet ILSAC GF standards usually meet similar API standards, but not always.” (From here.) Read also this and this.

So it’s not that any one brand is necessarily better or worse than any other brand, but there are differences in the details. Much of the time those differences don’t really matter, but sometimes they do. To eliminate any doubt, use an oil that’s officially approved by the vehicle manufacturer.

What Gary T said.

Here is more than you ever wanted to know about motor oil:

If you really want to get into the weeds w/regard to motor oil you might read up on the elimination of zinc (ZDDT) from most motor oils. The auto manufacturers pushed for this as it was thought that zinc negatively effected catalitic converters. Not sure if the EPA had their fingers in this decision. Anyway, conventional wisdom is that “zincless” motor oil does no harm to newer engines, especially those with roller lifters vs. flat tappet. Disagreement comes from many auto enthusiasts. Taking no chances, I use “diesel” motor oil in my 1970 Chevelle/El Camino. These products have retained the zinc. It’s available anywhere and it costs no more, you just have to purchase it in one gallon containers. I’ll have to check whether “diesel” motor oil impacts new car warrantees.

It will void a new car warranty because you can’t buy a conventional diesel-rated oil in a 5w-30 or 5w-20, which is what practically every new gas-powered car takes. You can get a diesel rated 5w-30 in a full synthetic, but these are a lot more expensive.

On some of the enthusiast boards I’ve frequented there’s people who will run 15w-40 diesel oils in their vehicles that call for 5w-30 so they can get the ZDDT, which I think is utterly absurd since even if there is some benefit to having it in there, it’s going to be cancelled out and then some by having an oil that’s totally inappropriate for that engine in that climate.

Heed Tim’s words and URL. This is probably the best resource for automotive lubrication that there is.

Having read the forums over there for several years, the general consensus is that if you get an API SM(or later) rated oil in the right viscosity range for your car (listed in the owner’s manual), and change it according to the recommendations, then you’re extremely, extremely unlikely to have oil related engine problems before something else vital on your car will totally crap out.

That being said, if you have a performance car of some sort- racer, Ferrari, etc… you can benefit from running the higher-end synthetics like Mobil 1, Pennzoil Ultra or Platinum, Amsoil, etc… They do have better stats, but like most things, those will only come into play at the very extremes of performance.

It’s a lot like tools; you can buy the high-end Makita tools, but most people aren’t going to even tax a Black & Decker, so why spend the extra $$? You know if you’re the kind that might actually kill a B&D tool, so you’ll go up, but so many weekend warrior types buy DeWalt and Makita, when Ryobi, Craftsman or B&D would have done the job adequately for a lot less money.