Using 5W40 instead of 5W20

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Unless you have engineering data to back it up I would stick with what the manufacture recommends.

Hearsay and feelings, and "I think", don't count.
 
Originally Posted By: MMasz
I‘m considering using Rotella T6 5W40 in my Expedition on my next change instead of 5W20. Will this affect my gas mileage?

Thanks in advance.

It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.

You will see most benefits from 5W-40 if you drive hard or do towing. Most engine damage occurs because of oil-film breakdown during high acceleration from a full stop. 5W-40 will help if this is your driving habit. Otherwise, 5W-20 should be OK for gentle driving and no towing, no uphill driving, etc.

As far as fuel economy is concerned, you will see little difference if you drive hard. If you drive gently, you will see about 1 MPG drop from switching to 5W-40.

If you do switch, Rotella T6 should be a good choice.
 
It won't hurt the engine. I'd use it in my beater, in fact I bought 6 cases of M1 TDT 5W40 for under $2/qt for that reason. I sold a few cases and have been using some of it. I would not use it in my Jeep which calls for 5W20, but that's just me. My 93 Aerostar has no complaints.
 
Originally Posted By: Gokhan
It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.


Same thing here in Australia. These are scanned images from my (original) owners manuals for
1. 2005 Mazda 2
2. 2005 Prius.



Uploaded with ImageShack.us
 
Last edited:
Originally Posted By: Gokhan
Originally Posted By: MMasz

It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.
You will see most benefits from 5W-40 if you drive hard or do towing. Most engine damage occurs because of oil-film breakdown during high acceleration from a full stop. 5W-40 will help if this is your driving habit. Otherwise, 5W-20 should be OK for gentle driving and no towing, no uphill driving, etc.
As far as fuel economy is concerned, you will see little difference if you drive hard. If you drive gently, you will see about 1 MPG drop from switching to 5W-40.
If you do switch, Rotella T6 should be a good choice.

Poor misleading advice.
No matter how hard ( meaning fast) you drive or how heavy a trailer you may tow is, there is ZERO benefit and many disadvantages (in addition to the 4 to 10% fuel economy drop) to running an oil two grades heavier than what the manufacturer (Ford) recommends. The reason is that it you will not be able to acheive oil temp's high enough to thin out the 40wt oil into the optimum range.
Even with the spec' 5W-20 oil, 99% of the time the oil will be thicker than optimum that's how high the viscosity safety margin is with the allegedly light oil grade.

But don't take my word for it, there isn't a well regarded member on this board that would support the notion.
 
Todays 5W-30 are at the low end of 30W, while most 5W-40 are middle or more 40W range. Going from a 5W-20 to a thinner 5W-30 is not that big a difference. Jumping to a 5W-40 IS and as I wrote earlier, IMO you will see a slight loss in MPG and performance.
 
Originally Posted By: MMasz
I‘m considering using Rotella T6 5W40 in my Expedition on my next change instead of 5W20. Will this affect my gas mileage?

Thanks in advance.


Yes it will...but it may or may not be significant. I am running 5w40 in my V10 Modular, but only because I had some leftover from another job. The F350 is such as gas hog that I have not noticed a difference in mileage.
 
Originally Posted By: Gene K
I really think we over think this. Most engines can survive on a variety of viscosities...

Indeed. I like to say that as long as the metal stays on opposite sides of the oil film, you're good.
 
I think there would be about a 2% decrease in fuel mileage. Whether or not you would notice it depends on how carefully you monitor fuel consumption. I don't think there is a need to jump 2 viscosity grades. Go to 5w30 if you are working the engine hard.
 
I've never noticed any change in fuel economy regardless of grade in the Expedition. 5w40 to 5w20. It is big, and it is heavy.

That said, mine has always gotten decent mileage for the breed.
 
Originally Posted By: CATERHAM
Originally Posted By: Gokhan
Originally Posted By: MMasz

It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.

You will see most benefits from 5W-40 if you drive hard or do towing. Most engine damage occurs because of oil-film breakdown during high acceleration from a full stop. 5W-40 will help if this is your driving habit. Otherwise, 5W-20 should be OK for gentle driving and no towing, no uphill driving, etc.

As far as fuel economy is concerned, you will see little difference if you drive hard. If you drive gently, you will see about 1 MPG drop from switching to 5W-40.
If you do switch, Rotella T6 should be a good choice.

Poor misleading advice.
No matter how hard ( meaning fast) you drive or how heavy a trailer you may tow is, there is ZERO benefit and many disadvantages (in addition to the 4 to 10% fuel economy drop) to running an oil two grades heavier than what the manufacturer (Ford) recommends. The reason is that it you will not be able to acheive oil temp's high enough to thin out the 40wt oil into the optimum range.
Even with the spec' 5W-20 oil, 99% of the time the oil will be thicker than optimum that's how high the viscosity safety margin is with the allegedly light oil grade.

But don't take my word for it, there isn't a well regarded member on this board that would support the notion.

You're only thinking about oil pressure and flow at high RPM. Most engine wear occurs not at high RPM but at low RPM and high torque -- in other words, acceleration from a full stop. In order to prevent metal - metal contact at such conditions, which is known as boundary lubrication, where the only protection is antiwear additives that coat the metal parts, you need to have a sufficient high-temperature, high-shear (HTHS) viscosity to prevent oil-film breakdown due to low RPM, low viscosity, and high torque. (Oil-film thickness is directly proportional to viscosity and rate of shear [RPM] and inversely proportional to torque.)

As I said before, in Europe, all grades between 0W-20 and 20W-50 are recommended for most engines that strictly call for 0W-20 in North America -- a whole range of four steps in oil viscosity.
 
Originally Posted By: CATERHAM
Originally Posted By: Gokhan
Originally Posted By: MMasz

It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.
You will see most benefits from 5W-40 if you drive hard or do towing. Most engine damage occurs because of oil-film breakdown during high acceleration from a full stop. 5W-40 will help if this is your driving habit. Otherwise, 5W-20 should be OK for gentle driving and no towing, no uphill driving, etc.
As far as fuel economy is concerned, you will see little difference if you drive hard. If you drive gently, you will see about 1 MPG drop from switching to 5W-40.
If you do switch, Rotella T6 should be a good choice.

Poor misleading advice.
No matter how hard ( meaning fast) you drive or how heavy a trailer you may tow is, there is ZERO benefit and many disadvantages (in addition to the 4 to 10% fuel economy drop) to running an oil two grades heavier than what the manufacturer (Ford) recommends. The reason is that it you will not be able to acheive oil temp's high enough to thin out the 40wt oil into the optimum range.
Even with the spec' 5W-20 oil, 99% of the time the oil will be thicker than optimum that's how high the viscosity safety margin is with the allegedly light oil grade.

But don't take my word for it, there isn't a well regarded member on this board that would support the notion.

4 to 10% you are on drugs. There are only a few people on this board I would have to agree with and they are not those who regurgitate factoids from oil 101. I have seen the insides of more engines from industrial to blown alky boat engines to have any article reader tell me otherwise.
 
Originally Posted By: uart
Originally Posted By: Gokhan
It won't harm your engine. In Europe they recommend anything between 0W-20 and 20W-50 for engines that strictly call for 0W-20 in US.


Same thing here in Australia. These are scanned images from my (original) owners manuals for
1. 2005 Mazda 2
2. 2005 Prius.



Uploaded with ImageShack.us
That is because everything is upside down in Aus!!!
27.gif
27.gif
crackmeup2.gif
 
Been there, done that, and not going back.

I owned a '99 F150 with the 4.6. I ran 5w20, 5w30, and 5w40 in it for year long periods.

There was no difference (statistical) in the fuel mileage between the 5w20 and 5w30.

5w40 resulted in a 7% drop in fuel mileage compared to the other two. Again, note this was over a 1 year period under similar usage.

Two points: It gets cold here, and my perception is the 40 weight was definitely too heavy in the winter here and resulted in significant drag. Second: I was also running similar experiments in my Jeep Cherokee at the time, and noted NO loss of fuel mileage in the 4.0l.

The UOA's were posted on the board way back when I did this. There was little difference between the weights. 5w40 cut the consumption down though.
 
Originally Posted By: Steve S
4 to 10% you are on drugs. There are only a few people on this board I would have to agree with and they are not those who regurgitate factoids from oil 101. I have seen the insides of more engines from industrial to blown alky boat engines to have any article reader tell me otherwise.


I know I'm not on drugs and I did note a 7% loss of fuel mileage in my case. Again, note that its gets cold here in the winter and 5w40 was not the solution for that issue in my case. Your mileage may vary...
 
Originally Posted By: MMasz
I‘m considering using Rotella T6 5W40 in my Expedition on my next change instead of 5W20. Will this affect my gas mileage?

Thanks in advance.


Minimally in the hottest parts of the summer.

More drag and pumping/power loss effect in the winter, and I would use something lighter for anything but summer.
 
Originally Posted By: crinkles
I've had my best mileages in 5 years using 15w-40.


Makes no sense, but me too. 15w40 (Schaeffers) in the Sienna - best mpg ever - close to 26mpg HW (very few data pts though). I now typically run slightly above 5w20 visc (mix of 5w30 and 5w20), and I see 23+mpg max.
 
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