Why wouldn't a 5w50 be better than a 5w40?

[BPU699]

Ive read tons of threads on here, and still don't get it... For any given car, the owners manual spec's possible oil grades...

Lets take the Mercedes m113 engine for example (used from 2002-2014 or so)...

Mercedes specs that you can use anywhere from a 0-30W, to a 20w50 in the owners manual, IN THE SAME ENGINE, based on expected temperature range... That's one helluva large range...

5w50, is specced to be used for -14F to 100F+.... so is 0w40. 20w50 "can" be used if lowest expected temp is 30 degrees...

In this scenario, other than possibly better gas mileage, why not use the 5w50? Especially if all you cared about was limiting wear...

I see arguments on line that bearing clearances in newer cars are "so tight" that thinner oils are recommended. Yet, its Mercedes that is saying the entire gambit of weights is "acceptable" and meets 229.1 and 229.3 spec...

The bearing clearances in my 1983 diesel Mercedes are .0001-.003 thou for the bearings. Uses a 15w40 or 20w50. Same as for my 1980's porsche (20w50), and the 2000-2014 BMW/MERCEDES cars. Yet, the diesel can use 20w50, even down to -20 degrees...

The newer Mustangs and corvettes spec 5w50 as the factory fill... and I am SURE they aren't running loose bearing clearances...

Years ago the 10w50 and 20w50 had tons of zinc, and damaged cats. Now, they have <1000PPM zinc, and are factory specced for new supercars...

So, what's the downside of 5w50? I see lots of folks using it in the Porsche community, and vette community...

I am specifically asking about daily drivers from about 2000-2015 , NOT racing situations or new toyotas with .0005 clearances...

Wouldn't the 5w50, used in the correct ambient temp range, make the car last longer? How could it "hurt"?

 

[y_p_w]

Because engines are inherently more tolerant of different conditions than most people think.

 

[QwikKota]

Because you can get Mobil 1 5W-40 in a 5 quart jug for a lot cheaper.

 

[BMWTurboDzl]

Ive read tons of threads on here, and still don't get it... For any given car, the owners manual spec's possible oil grades...

Lets take the Mercedes m113 engine for example (used from 2002-2014 or so)...

Mercedes specs that you can use anywhere from a 0-30W, to a 20w50 in the owners manual, IN THE SAME ENGINE, based on expected temperature range... That's one helluva large range...

5w50, is specced to be used for -14F to 100F+.... so is 0w40. 20w50 "can" be used if lowest expected temp is 30 degrees...

In this scenario, other than possibly better gas mileage, why not use the 5w50? Especially if all you cared about was limiting wear...

I see arguments on line that bearing clearances in newer cars are "so tight" that thinner oils are recommended. Yet, its Mercedes that is saying the entire gambit of weights is "acceptable" and meets 229.1 and 229.3 spec...

The bearing clearances in my 1983 diesel Mercedes are .0001-.003 thou for the bearings. Uses a 15w40 or 20w50. Same as for my 1980's porsche (20w50), and the 2000-2014 BMW/MERCEDES cars. Yet, the diesel can use 20w50, even down to -20 degrees...

The newer Mustangs and corvettes spec 5w50 as the factory fill... and I am SURE they aren't running loose bearing clearances...

Years ago the 10w50 and 20w50 had tons of zinc, and damaged cats. Now, they have <1000PPM zinc, and are factory specced for new supercars...

So, what's the downside of 5w50? I see lots of folks using it in the Porsche community, and vette community...

I am specifically asking about daily drivers from about 2000-2015 , NOT racing situations or new toyotas with .0005 clearances...

Wouldn't the 5w50, used in the correct ambient temp range, make the car last longer? How could it "hurt"?

Heavier grades increase heat and most importantly rob you of power. What you have to determine is the point of diminishing returns. Another thing is cost. Semi-synthetics in 20w-50 are cheap to produce.

 

[6.7 CTD]

More 40 weight options (you said no track use so 40w likely fine)

 

[randomhero439]

In the context of an older tech engine, the downside of thicker oil is reduced engine efficiency (less power, less responsiveness, more heat, more fuel consumption) at operating temperature, and slower lubrication during startup (which can cause increased wear). The upside is possible improvement in wear protection at operating temperature; however, just because an oil is thicker does not mean it will protect better. Once the oil can create a protective layer with an oil film and an additive package between the moving parts, higher viscosity isn't better. "As thin as possible, but as thick as necessary," as the saying goes.

 

[BPU699]

Not sure I understand your reply? So a 50w is better, or not?

Toyota initially spec's 0w20, then with increasing bearing failures went to a 5w20

Honda had bearing issues in the CRV (fuel dilution), and then recommended a thicker oil, and eventually increased the motor running temps...

As cars get up in miles, its safe to assume bearing clearances arent the same as new...

Why wouldn't a thicker oil protect better? The oil range spec's in the owners manual is for a NEW engine. And even the manual suggests a higher viscosity is ok...

So why not run a 50w instead of a 40w?

 

[BPU699]

In the context of an older tech engine, the downside of thicker oil is reduced engine efficiency (less power, less responsiveness, more heat, more fuel consumption) at operating temperature, and slower lubrication during startup (which can cause increased wear). The upside is possible improvement in wear protection at operating temperature; however, just because an oil is thicker does not mean it will protect better. Once the oil can create a protective layer with an oil film and an additive package between the moving parts, higher viscosity isn't better. "As thin as possible, but as thick as necessary," as the saying goes.

Question...

A thinner oil flows faster, so gets to the bearings faster...

But a thick oil "clings better" so its already there on start up? I thought that was one of the reasons toyota starting recommending 5w over 0w oils?

To clarify my question, I am interested in what can be done to keep high mileage engines healthy... At some point bearings do wear, and wouldnt a thicker oil at that point provide more "protection?

 

[BMWTurboDzl]

Question...

A thinner oil flows faster, so gets to the bearings faster...

But a thick oil "clings better" so its already there on start up? I thought that was one of the reasons toyota starting recommending 5w over 0w oils?

To clarify my question, I am interested in what can be done to keep high mileage engines healthy... At some point bearings do wear, and wouldnt a thicker oil at that point provide more "protection?

At really cold temps (sub zero) the 0w will require less effort to pump and less effort to turn the crank at start up.

IMHO seal hardening is the biggest issue with High Mileage engines. High Mileage oils have additional seal conditioners which attempt to keep seals from hardening to the point where they fail. Oil consumption is the second issue so bumping up a grade may help with that. I would run a High Mileage oil and occasionally rev out the engine on a long drive. Short trips and low speed trips can be hard on an engine.

 

[randomhero439]

Question...

A thinner oil flows faster, so gets to the bearings faster...

But a thick oil "clings better" so its already there on start up? I thought that was one of the reasons toyota starting recommending 5w over 0w oils?

To clarify my question, I am interested in what can be done to keep high mileage engines healthy... At some point bearings do wear, and wouldnt a thicker oil at that point provide more "protection?

If you can share where Toyota moved from 0w to 5w to have the oil "cling" to the metal parts when cold, that would be a very interesting read!

I'd just run the recommended viscosity and specification from the manufacturer, since that is likely what they used to validate the engine, and see if there are any signs of unhealthy wear. Consumption is an objective one. Noise is somewhat subjective and would need to be compared with a thicker oil (new vs new, same brand/chemistry) to see if there is a difference.

 

[I<3oil]

Honda had bearing issues in the CRV (fuel dilution), and then recommended a thicker oil, and eventually increased the motor running temps...

Source?

Honda is still speccing 0W-20 in the 2026 CR-V:

Recommended
·Honda Genuine Motor Oil 0W-20
·API service SN or higher grade 0W-20

 

[ZeeOSix]

A thinner oil flows faster, so gets to the bearings faster...

With a positive displacement oil pump, the oil is going to get there basically in the same time to all the force fed components if the W grade is the same in the same starting conditions. As long as you use the correct W rating for the start-up temperature then there shouldn't be a lubrication issue. A lower W rating will probably help lubricate the parts a bit faster that rely on splash lubrication instead of being force fed under pressure by the oil pump, but still nothing to worry about if the right W grade is used.

 

[Japanese]

With a positive displacement oil pump, the oil is going to get there basically in the same time to all the force fed components if the W grade is the same in the same starting conditions. As long as you use the correct W rating for the start-up temperature then there shouldn't be a lubrication issue. A lower W rating will probably help lubricate the parts a bit faster that rely on splash lubrication instead of being force fed under pressure by the oil pump, but still nothing to worry about if the right W grade is used.

Well, why then the most often oil failure is find at the camshafts and not at the crank/rod bearings?
Camshafts are the farthest from the oil pump as well.

 

[BMWTurboDzl]

Well, why then the most often oil failure is find at the camshafts and not at the crank/rod bearings?
Camshafts are the farthest from the oil pump as well.

Poor metallurgy and/or condensation from chronic short tripping.

 

[ZeeOSix]

Poor metallurgy and/or condensation from chronic short tripping.

And it could also be that some people run the wrong W grade oil and that can cripple lubrication on very cold start-ups.

 

[ZeeOSix]

Well, why then the most often oil failure is find at the camshafts and not at the crank/rod bearings?
Camshafts are the farthest from the oil pump as well.

It's not from using the correct W grade oil for the cold start-up conditions. If the correct W grade is used, the engine is going to be lubricated unless there is some kind major oil oiling system flaw with a specific engine that doesn't provide enough oil flow to all the force fed components when the oil is cold and thicker.

 

[tired]

Ive read tons of threads on here, and still don't get it... For any given car, the owners manual spec's possible oil grades...

Lets take the Mercedes m113 engine for example (used from 2002-2014 or so)...

Mercedes specs that you can use anywhere from a 0-30W, to a 20w50 in the owners manual, IN THE SAME ENGINE, based on expected temperature range... That's one helluva large range...

5w50, is specced to be used for -14F to 100F+.... so is 0w40. 20w50 "can" be used if lowest expected temp is 30 degrees...

In this scenario, other than possibly better gas mileage, why not use the 5w50? Especially if all you cared about was limiting wear...

I see arguments on line that bearing clearances in newer cars are "so tight" that thinner oils are recommended. Yet, its Mercedes that is saying the entire gambit of weights is "acceptable" and meets 229.1 and 229.3 spec...

The bearing clearances in my 1983 diesel Mercedes are .0001-.003 thou for the bearings. Uses a 15w40 or 20w50. Same as for my 1980's porsche (20w50), and the 2000-2014 BMW/MERCEDES cars. Yet, the diesel can use 20w50, even down to -20 degrees...

The newer Mustangs and corvettes spec 5w50 as the factory fill... and I am SURE they aren't running loose bearing clearances...

Years ago the 10w50 and 20w50 had tons of zinc, and damaged cats. Now, they have <1000PPM zinc, and are factory specced for new supercars...

So, what's the downside of 5w50? I see lots of folks using it in the Porsche community, and vette community...

I am specifically asking about daily drivers from about 2000-2015 , NOT racing situations or new toyotas with .0005 clearances...

Wouldn't the 5w50, used in the correct ambient temp range, make the car last longer? How could it "hurt"?

You've inadvertently stumbled into the answer to many new users' concerns about running thicker grades than what it spec'd. It's completely fine.

You will get increased wear protection with higher grades. The decrease in fuel economy probably won't be perceptible but will be small if it is. You may notice a tiny decrease in power, too, but probably not, because as you mention, Porsche forum posters use 50 grades all the time.

Why stop at a 50 grade though?

Why wouldn't a thicker oil protect better?

You are completely correct. It will.

 

[Japanese]

So, what's the downside of 5w50? I see lots of folks using it in the Porsche community, and Vette community...

Exactly!
There is no downside. People usually use such oil in sportscars or track cars. If you don't drive either of those then you don't need it. 30 or 40 grade oils will serve you more than well.

 

[BPU699]

If you can share where Toyota moved from 0w to 5w to have the oil "cling" to the metal parts when cold, that would be a very interesting read!

I'd just run the recommended viscosity and specification from the manufacturer, since that is likely what they used to validate the engine, and see if there are any signs of unhealthy wear. Consumption is an objective one. Noise is somewhat subjective and would need to be compared with a thicker oil (new vs new, same brand/chemistry) to see if there is a difference.

My error, Toyota never officially recommended this. Looks like there is plenty of discussion on the internet that in Europe they use the thicker oil as thats what recommended, but here, due to MPG/regulations, thinner oils are specc'd... No?

 

[BPU699]

Exactly!
There is no downside. People usually use such oil in sportscars or track cars. If you don't drive either of those then you don't need it. 30 or 40 grade oils will serve you more than well.

Wouldn't a high mileage older car have greater bearing clearances than new? Even though its not being raced, wouldnt a thicker oil have a benefit?