Switching back to 5W20 (SuperTech) for mpg!

Joined
Apr 5, 2016
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Texas
I dont like using the thin stuff but am forced to because of mpg concerns and trying to squeeze out the last bit. The 3.7 Liter Duratec calls for 5W20, but I have used 5W30 and 5W40 in the past. So I put SuperTech 5W20 Advanced in it and I notice immediately the engine is a bit peppier and faster. Seems to run better with the 5W20. My observations in the past was the thicker stuff quieted the engine down overall, but there was a bit of performance lag.

It seems like all my decisions nowadays are trying to increase the mpg with gas prices north of $3...lets hope the 5W20 can squeeze a little bit more mpg out of this engine.
You wouldn’t be able to feel, hear or see a difference between 5w30 and 5w20 in most cases.
 
Joined
May 21, 2018
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No perceivable MPG difference between 0w-20, 5w-20, 5w-30, 10w-40 and 5w-40 oil in all my vehicles. My engines do run smoother and quieter (I know, subjective) on the 40 grades and that's what I'm staying with. Too many other things influence MPG than oil grade.

Also, I expected a hit in MPG when changing out gear oil from 75w-90 to 75w-140. Again, no noticeable difference.

I think using synthetic fluids contributed to my results.
 
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A change that makes a small improvement may not be noticeable amid the noise of uncontrolled testing, but that doesn't prove it doesn't exist.
 
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The question is whether the small improvement is worth the potential additional wear, if that will bite you in the arse before you want to get rid of the vehicle.

I can rev it faster quicker, more performance, more win. Yeah, there is always a tradeoff even if it's just that you drive it more aggressively.

Maybe just buy the most appropriate viscosity for your engine and climate? I know, it's boring to do the right thing. Certain forums have many topics about being a masochist instead of just following time tested, proven... wait, do I smell nachos?
 
Joined
Apr 4, 2012
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Kendall, FL
Both are true between xW-20 and xW-30:
Lower hths absolutely gain you mpg.
Higher hths absolutely show less wear.

How significant are these differences in the real world? Way to many variables to conclusively respond either way.

But the OP knows what he feels and has experienced.
 
Joined
May 25, 2005
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ROCHESTER, NY
Let's say you own an older less efficient vehicle and you want to improve its fuel economy. OK?
This engine requires Oh IDK, lets say 5W30/10W30...

*And you change to a 5W20 or 0W20
*Check for sticking/binding anything, such as brakes
*Then you install a set(4) LRR tires on the vehicle
*Use the lowest octane fuel allowable...Or the highest octane, IDK!
*Drive more efficiently
*Clean out all of the heavy junk you've been carrying around and remove stuff that you don't use/need
*Properly running engine w/filters, new fluids for the tranny/diff etc.

Then, and only then may you see some fuel economy benefits. But, you better have a baseline/data to work with.
 
Joined
Apr 22, 2018
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A change that makes a small improvement may not be noticeable amid the noise of uncontrolled testing, but that doesn't prove it doesn't exist.
No it doesn't but this is an entirely backwards way of looking at this situation. The onus is on proving oil did have an effect and if you can't do that then the only responsible conclusion you can come to is you just don't know what effect oil grade has on MPG in this application. If you can't clearly separate the perceived effect from random variation you can't conclude there was an effect.
 
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... If you can't clearly separate the perceived effect from random variation you can't conclude there was an effect.
In that case, as is usual for uncontrolled seat-of-the-pants testing, you should pay attention to results of controlled tests performed by competent groups.
 
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In that case, as is usual for uncontrolled seat-of-the-pants testing, you should pay attention to results of controlled tests performed by competent groups.
...and we already discussed that in this thread. Expect a maximum of a 1% difference between grades and that means <0.5 mpg difference based on the average mpg for cars/light trucks in the US. Although, your mileage will vary, and for my vehicles it would be a maximum of difference of 0.14, 0.2, and 0.35mpg for each step up or step down in grade.
 
Joined
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...and we already discussed that in this thread. Expect a maximum of a 1% difference between grades and that means <0.5 mpg difference based on the average mpg for cars/light trucks in the US. Although, your mileage will vary, and for my vehicles it would be a maximum of difference of 0.14, 0.2, and 0.35mpg for each step up or step down in grade.
6 PSI in tire pressure buys me about 2 MPG I have never seen any increase in the use of thinner oil!
 
Joined
May 30, 2010
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North Carolina
...and we already discussed that in this thread. Expect a maximum of a 1% difference between grades and that means <0.5 mpg difference based on the average mpg for cars/light trucks in the US. Although, your mileage will vary, and for my vehicles it would be a maximum of difference of 0.14, 0.2, and 0.35mpg for each step up or step down in grade.
I would agree with this. In the past i have used 20wt to 40wt with no measurable difference in fuel mileage. Its probably there, but so small its lost in the normal variability of fuel mileage from tank to tank. Number of stops , idle time , throttle angle, road incline, temperature, wind resistance etc. , all these variabilities are more than the fuel savings of the thinner oil. Its not measurable in most situations.
 
Joined
Dec 27, 2019
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Nevada
6 PSI in tire pressure buys me about 2 MPG I have never seen any increase in the use of thinner oil!
Agree, tire pressure makes a difference. With colder temps now everyone should check their pressures.

As a general reminder to those who may not know, the recommended pressures are when the tire is cold.
 
Joined
Oct 22, 2009
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Agree, tire pressure makes a difference. With colder temps now everyone should check their pressures.

As a general reminder to those who may not know, the recommended pressures are when the tire is cold.
Yes the last time I checked mine was about two weeks ago when temps were running in the mid to high 40's since then we are running low to middle thirties I'll be my tire pressure has dropped.
 
Joined
Nov 8, 2003
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Cape Cod, MA
Yes the last time I checked mine was about two weeks ago when temps were running in the mid to high 40's since then we are running low to middle thirties I'll be my tire pressure has dropped.
My understanding is that every 10° change in temperature changes the tire pressure by 1 lb.
 
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