Why did I pick up 1.8mpg going to a higher viscosity oil ?

[Jetronic]

You spent more time driving downhill?

Probably not if you go home now and again....

 

[CheezWhiz]

I see great MPG increases when I drive with a tailwind. The headwind going the other direction doesn't make me feel as good about the MPG.

just drive whatever direction the wind blows. happy sailing!

 

[TiGeo]

My driving pattern is very consistent and my driving style is very consistent. I take the same path to and from work and rarely drive the car outside of this pattern. Here is my gas mileage per tank for the past year, with an average of 31.1 MPG:
29.2
30.1
33.3
33.7
32.4
30.4
32.8
31.1
30.9
33.1
30.6
30.9
30.4
31.6
33.5
30.3
31.6
32.7
30.1
32.2
30.3
30.3
26.5
29.8
31.2
30.7

The occasional increases into the 33s are due to slight deviations with more highway miles, or warmer, less windy weather. The dips below 30 MPG are during a cold spell from mid-January to early-February when temps approached 0. The one at 26.5 in particular, I remember having to idle my car for a long time a few mornings due to severe ice on the windshields.

Car is an '03 Civic 5MT that averages about 150 miles per week. MPG calculated at the pump with each fill-up. As you can see, there is no way a 1.8 MPG change would even register as a noticeable change in my data.

IMO you'd need a controlled environment such as having a computer drive the car on a dyno in an enclosed, temperature-controlled building with the same batch of fuel, in order to get meaningful differences.

Yep....I used to do the same. I had the same commute for 12 years. Nearly 100% no-traffic cruise control highway drive. I would drive it with CC on, at the speed limit, very controlled and do the same thing with the readout, no way you could discern small differences to the tenths decimal place in the normal variations. Over longer runs (say a year) you could see the summer/winter difference was about it.

 

[Hermann]

Have found that parking where the slope is either up or down can make a 2-3 mpg difference. Check my Fuelly

 

[Camperguy]

My driving pattern is very consistent and my driving style is very consistent. I take the same path to and from work and rarely drive the car outside of this pattern. Here is my gas mileage per tank for the past year, with an average of 31.1 MPG:
29.2
30.1
33.3
33.7
32.4
30.4
32.8
31.1
30.9
33.1
30.6
30.9
30.4
31.6
33.5
30.3
31.6
32.7
30.1
32.2
30.3
30.3
26.5
29.8
31.2
30.7

The occasional increases into the 33s are due to slight deviations with more highway miles, or warmer, less windy weather. The dips below 30 MPG are during a cold spell from mid-January to early-February when temps approached 0. The one at 26.5 in particular, I remember having to idle my car for a long time a few mornings due to severe ice on the windshields.

Car is an '03 Civic 5MT that averages about 150 miles per week. MPG calculated at the pump with each fill-up. As you can see, there is no way a 1.8 MPG change would even register as a noticeable change in my data.

IMO you'd need a controlled environment such as having a computer drive the car on a dyno in an enclosed, temperature-controlled building with the same batch of fuel, in order to get meaningful differences.

Just opened an account there, thanks for the info

 

[himemsys]

Just opened an account there, thanks for the info

Huh? Opened what account, where?

 

[himemsys]

Yep....I used to do the same. I had the same commute for 12 years. Nearly 100% no-traffic cruise control highway drive. I would drive it with CC on, at the speed limit, very controlled and do the same thing with the readout, no way you could discern small differences to the tenths decimal place in the normal variations. Over longer runs (say a year) you could see the summer/winter difference was about it.

My average for 2022 was 30.9 mpg. For 2023 it was 31.1. So far in 2024, it's 29.8.

 

[Camperguy]

Huh? Opened what account, where?

Fuelly.com

 

[Camperguy]

Dropped .1 over 446 miles

 

[Camperguy]

 

[Revving2Redline]

I went to 20W-50 redline in my diesel, from 0w-30 and didn't notice any negative change in MPG That's 50% more HTHS and KV.

Possible better sealing, wind direction, so many variables and too many for me to give the exact correct answer.

 

[ZeeOSix]

New filter ..... different media.
You just got a filter with media which is easier to pump oil through.*
* I am kidding

Even though you're kidding, if anyone is interested in the delta HP required to pump 8 GPM of oil at 70 PSI (use the hydraulic HP equation) through a filter with 2 PSI more dP than another filter, it's around 17 watts which is 0.23 HP. At normal cruising around speeds, the pump would probably only be putting out half of that flow rate and pressure, so cut the delta in required HP in half or more.

 

[Pablo]

Even though you're kidding, if anyone is interested in the delta HP required to pump 8 GPM of oil at 70 PSI (use the hydraulic HP equation) through a filter with 2 PSI more dP than another filter, it's around 17 watts which is 0.23 HP. At normal cruising around speeds, the pump would probably only be putting out half of that flow rate and pressure, so cut the delta in required HP in half or more.

I'm impressed.

 

[ZeeOSix]

Here's a plot of the gas mileage records from a vehicle I used to commute to work (80% highway, 20% city). The area of the red line is that same commute 95% of the time. Same oil and fuel always used. The MPG jumps around approx +/- 1 MPG over that time period. So IMO there would be too many other factors involved in the MPG fluctuation to nail down one specific cause of the fluctuation, like a change in oil viscosity. The drop in fuel mileage after the red line is due to not having that same commute anymore and driving became mostly city driving. Note - these were all calculated MPG, not from an on-dash MPG readout, which aren't that consistent either because on couple of other vehicles I've tracked the on-dash to the calculated MPG and they don't always track each other the same.

The only way you would ever see the effect of changing the oil viscosity on engine performance of fuel economy would be in a highly controlled test lab setup. Trying to determine it on the streets is way too uncontrolled. If you had long term data like this, you might be able to see a slight shift in the average trend, but even that would be questionable.

 

[TiGeo]

Here's a plot of the gas mileage records from a vehicle I used to commute to work (80% highway, 20% city). The area of the red line is that same commute 95% of the time. Same oil and fuel always used. The MPG jumps around approx +/- 1 MPG over that time period. So IMO there would be too many other factors involved in the MPG fluctuation to nail down one specific cause of the fluctuation, like a change in oil viscosity. The drop in fuel mileage after the red line is due to not having that same commute anymore and driving became mostly city driving. Note - these were all calculated MPG, not from an on-dash MPG readout, which aren't that consistent either because on couple of other vehicles I've tracked the on-dash to the calculated MPG and they don't always track each other the same.

The only way you would ever see the effect of changing the oil viscosity on engine performance of fuel economy would be in a highly controlled test lab setup. Trying to determine it on the streets is way too uncontrolled. If you had long term data like this, you might be able to see a slight shift in the average trend, but even that would be questionable.

View attachment 209256

Precisely. What people want is a nice line that has a drop at the point of whatever gadget/oil/additive/whatever they add that they swear up/down did something to the mpgs but in reality, you get what you show or the one I posted somewhere else in this thread...a bunch of noise b/c there are so many variables involved.

 

[ZeeOSix]

As I mentioned above, the on-dash MPG readout will not always be consistent either, so using the on-dash MPG readout is adding more randomness in the tracking. You have to do a hand calculation of at each fill-up (and try to do a consistent full fill-up) using the gallons shown on the pump and the mileage on the vehicles odometer. Here are plots of three vehicles I tracked like a hawk that had an on-dash MPG readout, and these plots show how the on-dash MPG readout can vary compared to the hand calculated MPG numbers. I always do a fill-up of the tank so I can get as consistent as possible hand calculations for MPG. Every vehicle will be different, so you'd have to do similar as shown below to be able to see how the on-dash MPG readout tracks to a hand calculated MPG.

 

[TiGeo]

On my VWs, I can adjust the dash readout to match (pretty close at least) the hand calc by applying a factor...-8% is the magic on the VWs I have that seems to bring them into line with one another.

 

[SammyChevelleTypeS3]

So my on my fifth fill-up and I picked up 1.8mpg going from 5w-20 to 5w-40 in my 14 JK. I've run PUP 5w-20 and PP Euro 5w-40 since. I know this isn't a scientific long term experiment but I honestly thought it was going to go down at least a mpg.
View attachment 206923

There are way too many variables which are not easy to control or even notice to attempt to blame oil changes / filter changes / etc..... on mpg increases or decreases. Everything from different blend gasoline. Different amount of gasoline in the tank. Different speeds (cruising and accelerating) and on and on. From warm weather to cool or cold weather. We all will even see slight better mpg in cooler weather. Even cruise control or not .... to more stop and go driving with more red lights or stop signs..... Highway vs street drives etc..... Of course one can expect to see slight difference in going from near water like oil grade to the thicker / heavy stuff since it takes more energy to move parts.

 

[ZeeOSix]

On my VWs, I can adjust the dash readout to match (pretty close at least) the hand calc by applying a factor...-8% is the magic on the VWs I have that seems to bring them into line with one another.

That's a good option, but as my plots show there is still some +/- accuracy going on even if you adjust the dash readout factor to the average error. If you start tracking the difference between the dash readout and hand calculations, you'll still see some +/- going on like my plots show. They show there is not a constant error factor, but a +/- error regardless of how close it is to the hand calculation.

 

[TiGeo]

That's a good option, but as my plots show there is still some +/- accuracy going on even if you adjust the dash readout factor to the average error. If you start tracking the difference between the dash readout and hand calculations, you'll still see some +/- going on like my plots show. They show there is not a constant error factor, but a +/- error regardless of how close it is to the hand calculation.

Yes I realize that...there always be some variation but the "oscillation" should get tighter. When I did all my tracking I should have always written down the dash tank mpg number vs. my hand calc...would have been interesting.