Fuel consumption up after oil change =(

gumpy · 06-09-2010, 08:31 AM

because i'm revving it sooo much!!! man the engine feels different after getting the factory fill out of it... I changed after 5000miles to RP and man there is a difference... Now i'm not saying RP made the difference i'm sure i'd get this effect with any other high quality oil but man... my fuel consumption is up 10% and loving it... Before it wasn't so happy reving past 5k... now it flies up to 6.5k rpm... it still doesn't like the 6.5k+ though... wonder if redline or some other oil will help...

Anyone else feel this effect or is it all in my head?

vipor · 06-09-2010, 08:36 AM

I recently switched to Redline after going through (2) Mobil 1 changes and I can honestly say I feel the difference. The car revs smoother and is quieter. It's a level 5 oil instead of a 4, but I bet the Esters have a lot to do with it.

Jordo! · 06-09-2010, 08:56 AM

Synthetic oil is a lot slipperier than dino oil; it's not unheard of to see a gain of ~1-2% in power on the dyno switching to synthetic do to reduced friction.

As to how it feels/sounds as you approach the red, my guess is that after 6.5K the motor is beginning to gradually lose torque, and without different heads/cams or a different VVEL tune, that's just the way it is.

Nick911sc · 06-09-2010, 09:25 AM

Quote:

Originally Posted by Jordo!

Synthetic oil is a lot slipperier than dino oil; it's not unheard of to see a gain of ~1-2% in power on the dyno switching to synthetic do to reduced friction.

As to how it feels/sounds as you approach the red, my guess is that after 6.5K the motor is beginning to gradually lose torque, and without different heads/cams or a different VVEL tune, that's just the way it is.

Wait what? Are you saying the change in oil is going to cause a loss in power on the top end of the motor? lol

Jordo! · 06-09-2010, 01:48 PM

Quote:

Originally Posted by Nick911sc

Wait what? Are you saying the change in oil is going to cause a loss in power on the top end of the motor? lol

No -- I'm saying that #1 - you'll see a slight gain (potentially) from running full synthetic (especially after the pistons and rings have fully worn in)

and

#2, if the VQ37 feels a bit rough as you approach redline it's due to design characteritics of the engine and there's not much you can do about it without using a different cam profile, different head maybe, or at minimum, retuned VVEL.

The OP noted it runs smoother around 5K but is still rough after 6.5, and he wondered if any oil could change that -- doubt it.

Modshack · 06-09-2010, 01:54 PM

Quote:

Originally Posted by Jordo!

The OP noted it runs smoother around 5K but is still rough after 6.5, and he wondered if any oil could change that -- doubt it.

It's just a notoriously rough motor. One of my only gripes with the car.

Jordo! · 06-09-2010, 07:19 PM

Quote:

Originally Posted by Modshack

It's just a notoriously rough motor. One of my only gripes with the car.

Heh heh -- you and Jeremy Clarkson

Sooner or later, someone will release cams or a super head port with stiffer valve springs -- I bet we'll see one making some power past redline eventually.

On that note, what's fuel cut on this car (haven't quite finished break-in)? Same for the MT and AT?

06-09-2010, 08:31 AM	#1 (permalink)
gumpy Enthusiast Member Join Date: Oct 2009 Location: Sydney Posts: 449 Drives: 09 370z white manual Rep Power: 16	Fuel consumption up after oil change =( because i'm revving it sooo much!!! man the engine feels different after getting the factory fill out of it... I changed after 5000miles to RP and man there is a difference... Now i'm not saying RP made the difference i'm sure i'd get this effect with any other high quality oil but man... my fuel consumption is up 10% and loving it... Before it wasn't so happy reving past 5k... now it flies up to 6.5k rpm... it still doesn't like the 6.5k+ though... wonder if redline or some other oil will help... Anyone else feel this effect or is it all in my head?

06-09-2010, 08:36 AM	#2 (permalink)
vipor A True Z Fanatic Join Date: Aug 2009 Location: Euless, TX [ DFW ] Age: 42 Posts: 13,531 Drives: Nismo 09-0183 QAB Rep Power: 49	I recently switched to Redline after going through (2) Mobil 1 changes and I can honestly say I feel the difference. The car revs smoother and is quieter. It's a level 5 oil instead of a 4, but I bet the Esters have a lot to do with it. __________________ 2009 NISMO # 0193 \| QAB \| Albums! \| 05.04.10 (Dynojet) 291.94hp/248.28tq Oil Cooler (DIY) \| Custom Headlights \| GTSPEC Braces \| F.I. Long Tube Headers

06-09-2010, 08:56 AM	#3 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Synthetic oil is a lot slipperier than dino oil; it's not unheard of to see a gain of ~1-2% in power on the dyno switching to synthetic do to reduced friction. As to how it feels/sounds as you approach the red, my guess is that after 6.5K the motor is beginning to gradually lose torque, and without different heads/cams or a different VVEL tune, that's just the way it is. __________________ Enjoy it. Destroy it.

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