Changed Diff/MT Trans Fluid to Motul 300 and super low MPG - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

jfg5067 · 03-22-2015, 01:10 PM

Just wondering if anyone else had effects such as this... I changed out both my MT fluid and differential to Motul 300, and went from 29 MPG to 23... Is this just due to a break in period of the new oil? Or just characteristic of this particular oil? Thanks!

stugray · 03-22-2015, 01:14 PM

I saw no change at all in mine. 30 MPG solid.

It's not the oil causing a 20% reduction in your gas mileage

Mad1723 · 03-22-2015, 02:28 PM

Tire pressure, driving habits, bad fuel, different weather can all change your MPG, but a bit of oil certainly wont! :P

jfg5067 · 03-22-2015, 03:08 PM

Just curious, I just checked tire pressures, I did bump up to 8 inch wide wheels and 255-40 tires... But doubt that's going to do that either... And I actually have been driving more conservatively

Chanpion · 03-22-2015, 04:36 PM

Quote:

Originally Posted by jfg5067

Just curious, I just checked tire pressures, I did bump up to 8 inch wide wheels and 255-40 tires... But doubt that's going to do that either... And I actually have been driving more conservatively

Still running Primacy HPs or something else?
If you're running something else, you've found your problem. The Primacy HPs are low rolling resistance tires.
'Usually' going to a thinner MTF fluid will increase fuel economy.

JB86'd · 03-22-2015, 06:38 PM

Quote:

Originally Posted by jfg5067

Just curious, I just checked tire pressures, I did bump up to 8 inch wide wheels and 255-40 tires... But doubt that's going to do that either... And I actually have been driving more conservatively

Heavier wheel and tire combo can definitely affect MPG...and a non LRR tire too.

Vracer111 · 03-22-2015, 08:44 PM

Quote:

Originally Posted by jfg5067

Just curious, I just checked tire pressures, I did bump up to 8 inch wide wheels and 255-40 tires... But doubt that's going to do that either... And I actually have been driving more conservatively

I think this bit of info should have really been in your first post - the gear and differential oil is not really causing your decreased fuel mileage... LOL

That's like someone saying they switched from Exxon to Shell fuel and noticed a decrease in the fuel mileage...then later posting "Oh yeah I also installed a turbocharger system with higher capacity/flow injectors at the same time...." LOL

jfg5067 · 03-22-2015, 10:44 PM

Except looking back, I did my wheels and tires first, and hadn't noticed a difference but had been driving highway only... then did the fluids change and have been driving local+highway... only noticing it greatly now... I am currently on 17x8 Enkei RP03 wrapped in 245**-40-17 Dunlop ZIIs... not LRR, but lighter combo than oem setup.

Mad1723 · 03-22-2015, 10:48 PM

Quote:

Originally Posted by jfg5067

Except looking back, I did my wheels and tires first, and hadn't noticed a difference but had been driving highway only... then did the fluids change and have been driving local+highway... only noticing it greatly now... I am currently on 17x8 Enkei RP03 wrapped in 245**-40-17 Dunlop ZIIs... not LRR, but lighter combo than oem setup.

Well, there's your explanation. You're comparing apples to oranges. City and highway driving, low-rolling resistance vs high grip tires.

n8dog11914 · 03-23-2015, 01:00 PM

It's the tires. Going from the Michelin Primacys to Bridgestone RE11As brought me down to about 23-24 as well.

Vracer111 · 03-23-2015, 11:28 PM

Quote:

Originally Posted by jfg5067

Except looking back, I did my wheels and tires first, and hadn't noticed a difference but had been driving highway only... then did the fluids change and have been driving local+highway... only noticing it greatly now... I am currently on 17x8 Enkei RP03 wrapped in 245**-40-17 Dunlop ZIIs... not LRR, but lighter combo than oem setup.

Your setup is over 3lbm heavier a corner than stock...with the tires ~6lbm heavier than the stock ones and in the highest performance level for street tire categories (Extreme Performance - which is designed for track use first, street use second.) Physics is physics... I'd easily wager the MOI is higher with that setup than stock, so it will take more energy to accelerate and stop than with the stock setup.

rice_classic · 03-24-2015, 12:17 AM

You added unsprung weight and increased your rolling resistance.

Result is too be expected. As least you can sleep well knowing nothing is wrong.

Muaddib · 03-24-2015, 01:47 AM

I noticed there are difference between different brand of gas. I am getting much better fuel economy with Shell V powaaaah.

AZP Installs · 03-27-2015, 09:42 AM

Tires and wheels over stock will make a HUGE difference. Therein lies your issue.

-mike

03-22-2015, 01:10 PM	#1
jfg5067 Member Join Date: Jan 2014 Drives: 2014 Subaru BRZ Limited Location: United States Posts: 30 Thanks: 3 Thanked 5 Times in 5 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	Changed Diff/MT Trans Fluid to Motul 300 and super low MPG Just wondering if anyone else had effects such as this... I changed out both my MT fluid and differential to Motul 300, and went from 29 MPG to 23... Is this just due to a break in period of the new oil? Or just characteristic of this particular oil? Thanks!

03-24-2015, 12:17 AM	#12
rice_classic Senior Member Join Date: Jun 2012 Drives: Nevermorange FRS Location: Seattle, WA Posts: 4,173 Thanks: 757 Thanked 4,208 Times in 1,808 Posts Mentioned: 78 Post(s) Tagged: 1 Thread(s)	You added unsprung weight and increased your rolling resistance. Result is too be expected. As least you can sleep well knowing nothing is wrong. __________________ SCCA T4 - FRS

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03-22-2015, 01:14 PM	#2
stugray Banned Join Date: Sep 2013 Drives: 2013 GBS BRZ Limited Location: Colorado Posts: 1,925 Thanks: 627 Thanked 1,445 Times in 711 Posts Mentioned: 41 Post(s) Tagged: 0 Thread(s)	I saw no change at all in mine. 30 MPG solid. It's not the oil causing a 20% reduction in your gas mileage

03-22-2015, 02:28 PM	#3
Mad1723 Senior Member Join Date: Jul 2013 Drives: Asphalt FR-S Location: Quebec, Canada Posts: 654 Thanks: 822 Thanked 418 Times in 222 Posts Mentioned: 6 Post(s) Tagged: 1 Thread(s)	Tire pressure, driving habits, bad fuel, different weather can all change your MPG, but a bit of oil certainly wont! :P

03-22-2015, 03:08 PM	#4
jfg5067 Member Join Date: Jan 2014 Drives: 2014 Subaru BRZ Limited Location: United States Posts: 30 Thanks: 3 Thanked 5 Times in 5 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	Just curious, I just checked tire pressures, I did bump up to 8 inch wide wheels and 255-40 tires... But doubt that's going to do that either... And I actually have been driving more conservatively

03-22-2015, 10:44 PM	#8
jfg5067 Member Join Date: Jan 2014 Drives: 2014 Subaru BRZ Limited Location: United States Posts: 30 Thanks: 3 Thanked 5 Times in 5 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	Except looking back, I did my wheels and tires first, and hadn't noticed a difference but had been driving highway only... then did the fluids change and have been driving local+highway... only noticing it greatly now... I am currently on 17x8 Enkei RP03 wrapped in 245**-40-17 Dunlop ZIIs... not LRR, but lighter combo than oem setup.

03-23-2015, 01:00 PM	#10
n8dog11914 Senior Member Join Date: May 2012 Drives: 2013 WRB Subaru BRZ 6MT Location: Fort Mill, SC Posts: 272 Thanks: 46 Thanked 72 Times in 58 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	It's the tires. Going from the Michelin Primacys to Bridgestone RE11As brought me down to about 23-24 as well.

03-24-2015, 01:47 AM	#13
Muaddib Mentat Join Date: Jun 2013 Drives: 2013 Scion FRS 6MT Location: Vancouver Posts: 542 Thanks: 666 Thanked 358 Times in 198 Posts Mentioned: 4 Post(s) Tagged: 0 Thread(s)	I noticed there are difference between different brand of gas. I am getting much better fuel economy with Shell V powaaaah.

03-27-2015, 09:42 AM	#14
AZP Installs Join Date: Oct 2011 Drives: '11 STi->'14 BRZ \| '14 Touareg TDi Location: Kenilworth, NJ Posts: 1,269 Thanks: 359 Thanked 558 Times in 371 Posts Mentioned: 49 Post(s) Tagged: 0 Thread(s)	Tires and wheels over stock will make a HUGE difference. Therein lies your issue. -mike

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