Comments on: What Do the Numbers on Motor Oil Mean?

By: Sean

Sean — Tue, 16 Aug 2022 19:47:11 +0000

In reply to Rick. I doubt the 5 point difference between 5W-40 and 10W-40 was enough to cause engine failure, especially in such a short amount of time. They both run at the same viscosity at operating temperature.

By: Rick

Rick — Sun, 14 Aug 2022 12:02:57 +0000

If you take your car to a garage to have your oil changed, make sure the kids changing your oil understands the importance of these two numbers. My wife took her 2013 VW Passat to a tire shop to have her oil change. My son over heard the conversation between the two boys. Once said “we don’t have any 5W-40 and the other said “Oh, just use the 10W-40”. Unfortunately my son didn’t say anything at the the time. In a matter of a week or two we had to replace a $6,000 engine and couldn’t prove that they used the wrong oil. The engines of today have such tolerances that difference between 0W, 5W, and 10W are huge.

By: Sean

Sean — Tue, 22 Mar 2022 04:59:01 +0000

In reply to Victor.

Oil at operating temperature is much thinner than cold oil, even though the number on the right is a higher weight (i.e. more viscous).

SAE 30 oil at cold or ambient temperatures would be very thick; far too thick for most engines. SAE 10 at operating temperature is far too thin, and would not properly lubricate the bearings.

10W30 is a compromise between the two. The additives in the oil are formulated so the oil behaves like SAE 10 in cold temperatures, but it behaves like SAE 30 at operating temperature. It is essentially the best of both worlds.

By: Sean

Sean — Tue, 22 Mar 2022 04:49:24 +0000

In reply to jenn ross.

The number on the right is most important. The number on the right is the weight of the oil at operating temperature. The “W” stands for “winter”, so the left number indicates the weight of the oil in colder temperatures (i.e. when you first start the engine).

Check your owner’s manual for your vehicle to see if 5W30 can be used in place of 5W20. It’s probably fine, but I would follow the manufacturer’s recommendation on that.

By: Victor

Victor — Sat, 19 Mar 2022 18:44:34 +0000

you say:
The number to the left of the W refers to the oil viscosity when the temperatures are low. The number to the right of the W refers to the oil viscosity at hotter temperatures.
question:
In the case of 10W-30, does that mean that this oil has a higher viscosity at a hotter temperature, since 30 is greater than 10?
The answer given is: NO… And that’s it!
So, what does it mean? nobody explains, can you?
Thanks

By: jenn ross

jenn ross — Fri, 18 Mar 2022 15:37:55 +0000

This is a fantastic explanation of something we all take for granted until the day we actually need to add oil to our vehicles.Otherwise we rarely ever think of such things . Like today but I am still a bit uncertain if I have to use the 5w-20 called for on the vehicles oil cap or if it's IK to use the 5w-30 that I have on hand? Also, which number, right or left, is more important to pay attention to?

By: Sean

Sean — Mon, 16 Aug 2021 16:30:49 +0000

In reply to Victor Ye Swe. When in doubt, use the oil weight that is recommended in the owner's manual. If you've lost the owner's manual, you should be able to find a digital copy by searching online.

By: Victor Ye Swe

Victor Ye Swe — Mon, 16 Aug 2021 06:33:48 +0000

My country is in tropical zone.toyota Porte 2008 1.3 engine,workshop always use 10w 30 .Is it ok for my car?

By: autotechnician

autotechnician — Mon, 21 Oct 2019 16:23:36 +0000

In reply to Lynn. That's really not much of a difference. You'll be fine.

By: Lynn

Lynn — Sun, 20 Oct 2019 08:20:28 +0000

I’ve Always used 5w30 castrol
Oil in my 1994 cutlass.
They put in 10w30.
Will this hurt my engine.
I’m in a lower climate area also.