Age old question, 5w20 vs 5w30

[Fiesta fan]

Hello everyone,

Still a relatively new member of this community, and finally got my 2019 Fiesta ST I was looking for just 13 days ago.

(Updated post in case anyone was following my new member introduction post)
https://www.fiestastforum.com/threads/greetings-from-las-vegas.32519/

With that out of the way, I feel like I'm going to get ripped in half for asking this question. But, I have done my due diligence and searched multiple threads regarding this topic on this forum, and even doing research outside of the forums to see what everyone is saying.

From what I've seen so far...I've learned that (Please correct me if I'm wrong)
1. Apparently the 5w20 weight is used to achieve better mileage...? Or at least that's what Ford was aiming for when they put it on the owner's manual.
2. 5w20 is used mainly for colder climates, but even so people are deciding to go 5w30

I have seen many people either stay true to the 5w20 or change to 5w30. I've also heard some people mention benefits outside of performance for going to 5w30 instead (like less noise and rattle).

I plan to daily the fiesta for the most part and currently reside in Las Vegas, so we're in our colder months right now. But "cold" is only about 45-50 degrees Fahrenheit here. No track use, but like to go for light spirited drives from time to time.

My mind is saying 5w30, and plan to go for this at my local Wal-mart but just want to make be 100% sure before I go forward with it: https://www.walmart.com/ip/Pennzoil...uart/139680614?classType=VARIANT&athbdg=L1102

With all that being said, I turn to you my fellow Fiesta fanatics. Would you go for 5w20, or 5w30? Any input is greatly appreciated!!

 

[ShakenCoffee]

I'm no expert, but I've been using Pennzoil Ultra Platinum 5w-30 and have been happy with it. However, I've only put on about ~9k miles since I bought my car, so no long term experience. I've only had some fuel issues, unrelated to oil. Here's a good video on the difference of the Ultra Platinum vs Platinum:

View: https://youtu.be/hqBJQ23NFYc?si=ygN7EBaXDTNVL80i


I did spend about 3 months trying to find the best oil and oil weight before my first oil change. I landed on sticking with 5w-30, obviously there's many brands that can be argued to be better than others. What helped me come to a decision for the brand was comparing all of the specs/additives of different oils, and comparing it to what results show are generally better for our engines (and also taking price into consideration) . For reference, I am in SoCal, so no cold weather.

 

[pixelzombie]

This is the first I'm hearing of benefits when using 5w30. I do use a larger K&N oil filter, and there have been reports of that additional oil helping to reduce oil temps.

 

[Capri to ST]

I believe in sticking with what the manufacturer recommends, which in this case is 5w20. I feel more comfortable with that .
There is some talk that a thin oil like that is recommended for better gas mileage, but I can't believe that a manufacturer would jeopardize the safety of its engines just for some minuscule extra amount of gas mileage.
I've read that modern engines have tighter manufacturing tolerances than engines used to, and that is one reason that viscosities have become lower over time, to be able to get into the tighter spaces. According to an Amsoil blog-
"modern engines are built with tighter tolerances than older engines. For example, the spaces between the crankshaft journals and main bearings are smaller.
Many newer engines also use variable valve timing (VVT) to improve fuel efficiency and reduce emissions. Many systems require the motor oil to flow through tiny solenoid openings to actuate VVT components. Oil that’s too thick to flow through these openings can cause problems and trigger a check-engine light."

I've also seen extensive interviews with some of the engineers who designed our cars, and I was impressed by the thoroughness and level of thought that went into every aspect of it, even small ones. I would hope and think that the same level of care went into a major choice, that of oil viscosity.
Whichever one you choose, you obviously want to use a high quality full synthetic, I don't think that is in debate.

 

[lemonjs]

For the last 7 years I have always used Castrol Edge 5w30 with FoMoCo oil filters. In that time I’ve done 50,000 miles and around 25 track days with no issues, so this oil gets my vote!

 

[Sam4]

I believe in sticking with what the manufacturer recommends, which in this case is 5w20. I feel more comfortable with that .
There is some talk that a thin oil like that is recommended for better gas mileage, but I can't believe that a manufacturer would jeopardize the safety of its engines just for some minuscule extra amount of gas mileage.
I've read that modern engines have tighter manufacturing tolerances than engines used to, and that is one reason that viscosities have become lower over time, to be able to get into the tighter spaces. According to an Amsoil blog-
"modern engines are built with tighter tolerances than older engines. For example, the spaces between the crankshaft journals and main bearings are smaller.
Many newer engines also use variable valve timing (VVT) to improve fuel efficiency and reduce emissions. Many systems require the motor oil to flow through tiny solenoid openings to actuate VVT components. Oil that’s too thick to flow through these openings can cause problems and trigger a check-engine light."

I've also seen extensive interviews with some of the engineers who designed our cars, and I was impressed by the thoroughness and level of thought that went into every aspect of it, even small ones. I would hope and think that the same level of care went into a major choice, that of oil viscosity.
Whichever one you choose, you obviously want to use a high quality full synthetic, I don't think that is in debate.

Ask Hyundai about manufacturing for extra mileage. We go thru a ridiculous amount of oil with their DI engine (clean tailpipe!). They've bumped it out to 150k warranty, but no way are they going to accept my oil change paperwork. Don't accuse ford of being any smarter - looking at you EV mustang...

 

[atlantaM3]

My recollection is that this engine is spec'd for 5w-30 in the EU, AUS, etc. The only place that requires 5w-20 for it is the US for mileage/emissions purposes. So something to consider.

I recently swapped to 30 weight, and it is notably quieter in operation in general driving.

Recall that the manufacturers interest is getting the car certified with the best MPG and emissions rating possible, through the warranty period. After that, they do not incur repair/maintenance costs. For example, look at how many fluids they say are 'lifetime fill', such as early PTU's. They definitely needed the fluid to be replaced, but would make it through warranty period before general failure. After that, so what? It's all a numbers game by the corp actuary's to model potential loss.

 

[pixelzombie]

I checked the Euro spec's and they also recommend 5W20

 

[Stubborn Approach]

Given that I spend half the year driving all day in triple digit heat, I would never run 5w20 oil. I couldn’t care less what the manufacture thinks I should be running, I’ve already spent thousands of dollars improving on their compromises all over this vehicle, so 5w30 it is. Might even go with 5w40 for summer track days if I don’t like the temp data after installing a real oil cooler. I feel anyone that watches the temps the vehicle provides in those summer temps would come to the same conclusion. Feel free to look at the oil analysis thread or have your oil analyzed for more piece of mind in your decision.

 

[Dialcaliper]

Given that I spend half the year driving all day in triple digit heat, I would never run 5w20 oil. I couldn’t care less what the manufacture thinks I should be running, I’ve already spent thousands of dollars improving on their compromises all over this vehicle, so 5w30 it is. Might even go with 5w40 for summer track days if I don’t like the temp data after installing a real oil cooler. I feel anyone that watches the temps the vehicle provides in those summer temps would come to the same conclusion. Feel free to look at the oil analysis thread or have your oil analyzed for more piece of mind in your decision.

A 30wt oil is fine, but I’d be cautious going to a 40wt oil unless you’re absolutely sure the engine will be running hot and you have a proper oil temperature gauge.

Modern engines run tighter clearances than those of old, and the risk is that if you go out on a day where temperatures are mild and the engine is running at “normal” temperatures, you’re actually more likely to experience oil shearing (faster breakdown) and potentially oil starvation. Higher viscosity is only better until it can no longer flow where it needs to be.

Oil weights are a funny measurement as they change a lot with temperature and “W” oils are a bit misleading - for example at startup temperatures, a 0W30 is actually in between 5W20 and 5W30, because the 0W measurement only applies at something like -30C

The difference at most operating temperature from 5W20 to 5W30 is actually pretty small. Similar viscosity at about 5C higher temperature. However the jump to 5W40 is something like +25C (+45F) hotter for equivalent viscosity. So unless you really have evidence that you’re running oil 20-25C hotter at the same coolant temperatures, you’re treading in dangerous waters and 5W30 is more than enough.

https://penriteoil.com.au/knowledge-centre/Viscosity/237/what-is-an-sae-viscosity/180

 

[WannabeST]

I drive an SE not an ST however, Ford recommends 5W20 in my car also. It's pretty well known that lower engine oil weight is typically (but not always) is done for fuel economy purposes. All of my vehicles see lots of miles, lots of abuse and lots of G forces on the track. (I just did 5 track days on my car this month alone, one of those I drove the car 8 hours to the track and 8 hours back) Ever since I bought my car I have put Valvoline 5W30 in it. I would need to recount, but I believe I am at, or near 40 track days on this car specifically. I have never had any mechanical failures and I still average over 40 mpg while cruising the highway on the way to the track or around town. I find more peace of mind in doing what's safer for the engine wear wise vs mpg.