5W30 vs 5W40: Determining Which Motor Oil Is Right For Your Car

A majority of car owners take their vehicles to a garage for an oil change, or if we try to do it ourselves, we often browse through the menu and use whichever oil the manufacturer recommends. Although there is nothing wrong with either scenario, knowing a little about what goes on with your vehicle and having some information regarding the best motor oils for your car is always a good idea as this information can come in handy. Here, we will be comparing the specifications and properties of engine oils 5w30 and 5w40 so you can have a better idea about which oil to use for your car.

Difference between 5w30 and 5w40

The Society of Automotive Engineers (SAE) has established a statistical code for determining motor oils in accordance with their viscosity characteristics, ranging from low to high: 0, 5, 10, 15, 20, 25, 30, 40, 50, and 60. Viscosity is a liquid’s resistance to flow. Liquids that are thin and runny (like water) are assigned a lower viscosity whereas liquids that are thick and consistent (like honey) are assigned a higher viscosity value. The numerical 0, 5, 10, 15 and 25 are postfixed with the alphabet W, which stands for “winter”, or low temperatures, and not “weight”.

Remember that engine oil changes in viscosity measurements when putting under different temperatures, i.e. depending on the weather outside. When it comes to kinematic viscosity, the numerical values are assigned based on the oil’s ability to flow through an average orifice, at regular temperatures. The longer it takes for the oil to pass through, the higher the SAE code is assigned due to the higher viscosity, which means the 5w40 has a higher viscosity than 5w30.

Read more about the difference between 0w40 vs 5w40.


Quick Summary: Best 5w30 and 5w40 Motor Oils

Why Is Thickness Important?

Why Is Thickness Important?

Oil is the lifeblood of any motor, but you cannot get away with using just any motor oil because its thickness plays a great role in its efficiency. The thickness or viscosity determines how well the oil will flow through the engine. The higher the initial number, the thicker or viscous the oil is. Thus, if you live in colder environments or freezing temperatures, you should use thin grade oil, such as the 5w30. All vehicles have a particular oil viscosities/weight, and you can usually find this information on the top of the crankcase, usually on top of the oil cap.

To keep your motor up and running at all times, you should stick to the mechanic’s or manufacturer’s recommendations regarding motor oil. Thinner motor oil flows more smoothly and quickly when the engine is cold, which is why you should not use anything less than 5W-30 in the summer.

There is no dearth of motor oils that deliver high performance and withstand extreme temperatures, dirty climates, and aggressive driving. Keep in mind that high-quality motor oil lasts longer and you will have to schedule an oil change for later as compared to using any generic brand. It is recommended that you keep 5W motor oil on hand before the first gust of cold strikes.

5W Viscosity

5W viscosity grade calls for the lubricant to properly flow at lower temperatures as compared to, for instance, oil with 20W viscosity, hence you should use it when the weather is cold.

5W Viscosity

Single Grade vs. Multi-Grade Oil

When the oil heats up, it gets thinner. Single grade oils become too thin when they come into contact with the heat produced by the car’s engine, and this is where multi-grade oil comes in. The idea of this motor oil is simple: use physics and science to stop the base oil from becoming too runny and thin when the engine heats up. The number prior to the alphabet W shows the ‘cold’ viscosity rating of the oil whereas the number after the alphabet W shows the ‘hot’ viscosity rating.

5W30 Motor Oil

5w30 is one of the two most commonly used types of motor oils for various reasons. First, it works surprisingly well with a broad selection of vehicles with different engine types. Second, the oil also covers a diverse range of possible temperatures but is ideal for warmer temperatures. For the most part, the oil works smoothly regardless of the vehicle and the temperature.

5W40 Motor Oil

Although 5w40 is not as common as 5w30, it certainly does have quite many admirable features that optimize the health of your engine, some of which include:

  • Protecting the engine from deposit and sludge buildup and damage
  • Ensuring the engine revs to life quickly in colder environments and the oil circulates efficiently in freezing temperatures
  • Getting to moving parts of the engine fast

The 5w40 acts like a 5-rated single grade oil when it’s cold, but it does not become thin any more than 40-rated single grade oil when it’s hot.

5W30 vs. 5W40

When it comes to choosing between 5w30 and 5w40, many people prefer the former. This is because the 5w30 motor oil has a smooth effect on the oil pump and also a more suitable flow through the engine when hot. However, both these motor oils work great for providing faster lubrication to engine parts when you start the car.

5W30 vs. 5W40

So, if we dig in into technicalities, the number ‘5’ in both oils represents the same viscosity when the engine is cold (startup temperature), but in case of 5w30, the ’30’ represents a lower viscosity when the engine is operating at high temperatures as compared 5w40, which has a higher viscosity.


If you are racking your brain to choose between 5w30 and 5w40, we recommend you go with 5w30. However, if it is too expensive or not available for use, you can always go with the 5w40, which is just as good and will not cause any damage to the engine parts.

Jason Trevino

Jason is a talented and advanced author, blogger and auto expert. He is determined in researching thousands of products so as to make it easy for the owners to find the best products. He focuses on giving users better understanding on products they are using and ones they anticipate to buy.

Click Here to Leave a Comment Below 29 comments
Ole Steen - April 7, 2017

Hi Jason

I’m in the middle of a terrible mess exactly about your theme and I hope you can help me out.
My Fiat 500S (Twin Air 0,9/85hp) runs 5W-40. What will happen if I change to 5W-30 instead?

Best Regards
Ole Steen

Abhai - April 18, 2017

Excellent Information..

Rick Dunn - April 26, 2017

I have a 2015 Smart, gas engine. The manual calls for 0W40, but, I have a hard time locating Mobil 1 oil, is 5w40 ok to use?

Tranxene - May 3, 2017

I own a 2002 Jaguar XJR which is supercharged. I just had the oil changed. I asked for synthetic 0w40 oil. After I got home I noticed they had put 5w30 synthetic in. Is that adequate for the supercharger? If so I wI’ll run it until the next scheduled change. If not I will have it changed now. Thanks for the help.

    jonny big lunchbucket - September 15, 2018

    NO, it will damage your engine…! The oil needs to be thin on startup in order to get into the variable valve setup. WHAT JERKS

Rajul Singh Parihar - May 4, 2017

My Fiat Multijet 1.3 Diesel engine manual recommends 5W30 or 5W40 ( but 5W30 is preferred)
but what should i use , I heard somewhere to use 5W 30 if we want nice Average and performance , but if we want longer engine life then use 5W 40

why ? Is that so ..

Rajul Singh Parihar - May 4, 2017

By the way , I am from INDIA , we normally don’t have freezing temperatures over here in winters ,

please reply to me , which one should i use 5W30 or 5w40

    carlos - August 22, 2017

    go for 5w40 not too thick just the right viscosity for most vehicles

    Dheeraj Darolo - February 14, 2018

    Hi Rajul
    using a 5w40 would be better cause the temperature in India varies from falling to 0°C like up North and going as high as 45°C in places in the interior like Nagpur etc.
    Depending on ur location and AVG temperature changes 5w40 would give you an all round all weather protection.

YINKA LAWAL - October 10, 2017

hi, i use a lexus rx 350 2007, i use mobil 1 RSP FORMULA 5w30. is this oil ok for my lexus

thank you.

miro - October 19, 2017

and what about mix 50/50% is it possible to mix it? and create 5w35?

I would do it

Czech Republic geek

David - November 2, 2017

The second number (30 or 40) are the thickness when the oil is at 212°f, which is the normal temperature of the engine, independent from outside temperature, no matter if it is freezing or boiling outside, the engine is configured to run at around 212°f.
At that temperature 20 is too thin and 50 is to viscous, 30 is the right viscosity for an engine running at 212°f. So why there is 40 or 50 or 60 grade oils, well, that comes to play when you are a spirited driver or when you track your car, so the internal temperature of the engine is over the normal 212°f, so you can have 40 or 50 or 60 grade oil, and at race temperature, for example, 300°f or more, you need a 60 grade oil so it does not get too thin.
The first number is the viscosity at 0° celcius, so 5 is better than 10 and 0 is better than 5.
I use Pennzoil Platinum Euro 5w40 in my e90 BMW (Approved BMW LL-01 Oil) because i sometimes drive a little spirited.

    sergio - January 22, 2019

    Hello David
    just to ask if you still using Platinum Euro 5w40? I use the same on my 2007 328i. my country is very hot, so I think I am protected with this.

talah - December 30, 2017

hi. can any one advice me which is best oil for M16A engine from 5w30 and 5w40 for almost 30 dig centigrade to 50 dig centigrade temperature areas.

Joe - January 4, 2018

Thank you Sir – I am from South Africa. I have a petrol engine BMW 120i (2006 model with E87 engine) You just helped me very nicely in deciding which fully synthetic oil to choose for my vehicle. We have the Castrol range here which is very popular and I will go with the 5W-30

    Sphamandla Shezi - April 9, 2018

    Thank you, good information.

john - March 24, 2018

I live in dubai its very hot here most of the year arrround in summer it can reach 50 degree , may i know whats the best option for this condition 5w30 or 5w40?

Please advice


    ush - June 28, 2018

    For your weather, go for a 5w40. As you can see in the chart above, that viscosity is ideal for most vehicles.

Ozman - April 14, 2018

Hi i have subaru wrx sti type uk 2017 i want to change but oil but don’t know which one to buy 5w30 or 5w40 please help me out to buy the right oil thank you.

Tur - June 20, 2018

Hello , i will need some help here, Basicle i have a BMW e39 525d , and i don’t know what oil is better for my engine 5w40 or 5w30 ?
Any sugestions , help ?

Adnan - August 14, 2018

For high temperatures in Dubai 40+ degree i suggest to use 5w40 or 10w40 in peak summer time but or normal winter temperatures i will preffer to use 5w40 so all year round 5w40 is best for hot temperatures

Michael - November 28, 2018

I have a 1993 Mitsubishi Delica. In New York State should I use 5-30, 5-40 or 10-40. Conventional or synthetic?

    Gary - December 14, 2018

    Since you have an older car, the engine is most probably quite worn, and NY summers get quite hot, so an oil that is thicker at hot temps should protect your engine better. As such, 5W-40 would be thicker and more protecting at hot NY summer temps than 5W-30.

Rhianna Hawk - January 9, 2019

My husband just got a very high-quality new sports car, and we’re trying to decide what kind of machine oil to get for it. I had no idea that the viscosity could change according to the weather and temperature outside, but we’ll definitely remember that the values given are based on normal temperatures, as you said. It certainly seems that the 5W40 covers a greater temperature range than the rest, and though it’s good to know that oil generally works well regardless of temperature, as you said.

Ultramod - January 12, 2019

Hi very interesting article.

I have BMW e92 330i 126k I was debating about slightly thicker oil currently using 5 30, but debating using 5 40.
(5,30 BMW recommends but Castrol recommends 5,40.)I suspect both are fine. My logic for slightly thicker was more to to do with age and mileage. as the components are wearing slightly thicker would suit an older higher mileage engine.
I’ve settled on sticking to 5,30 as i do regular short commute to work so think as the engine is running lower temperature will suit it better.

Dennis Warren T Fernandez - January 16, 2019

Hi, I’ve got a 2008 model altis and have a 103+km mileage, need to know what is the best oil that I need to used? appreciate your best recommendation.

Rakesh Ravindran - February 21, 2019

I have a Suzuki S-Cross with a Fiat-derived 1.6l MJD Diesel engine. The company recommended is 0W30. Since the place where I live, the temp varies between 15degC in winter and almost 40-45degC in summer, is it advisable to go for 5W30 or 5W40?

Many thanks in advance,

San - December 23, 2021

I would recommend 5w-40 oil for any vehicle with 80000km or more on the odometer. Protects engine better. As long as you do regular changes, like 5000-7000km depending on use.

5w30 engine oil - February 7, 2022

Hi Jason

I’m in the middle of a terrible mess exactly about your theme and I hope you can help me out.
My Fiat 500S (Twin Air 0,9/85hp) runs 5W-40. What will happen if I change to 5W-30 instead?


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