3mpg loss with GC

[MrWideTires]

I used to use edge 5w30 and then switched to their 0w20 for the winter.. Always averaged 28.4mpg on the highway going 75mph with cruise in my SpecV. Now since it has 106k miles I decided I would switch to GC and my mpg instantly dropped to 25.6mpg under same conditions.. I love GC but not when it's gonna cost me 3mpg when driving 35k a year..

 

[dparm]

GC is thicker than Edge 5w30, and a lot thicker than the 0w20. And with higher HTHS values, it is definitely thicker at high temps.

Surprised you dropped 10%.

 

[Torquejumper]

Are you sure it's the oil? Maybe there are other factors that affect gas mileage (e.g. driving habits, quality or type of gas, weather conditions etc). In my opinion, I wouldn't contribute the 3mpg loss to the oil you're using. Based on my experiences with different oils in the Spec V, oil viscosity tend to have very little effect on gas mileage nor power. I have ran both 5w and 10w-40 synthetic on my Spec V, and I can still squeeze out 31mpg all highway driving 70mph on cruise control; that's with a header and intake.

Have you heard about the precat and butterfly screws problem on the 02-06 Ser and Ser Spec V?

 

[rshunter]

GC can definitely impact mileage. I took a hit when I went from M1 AFE 0w30 to GC in my 4.7L V8. I can't say it was 10%, but it was indeed significant.

 

[MrWideTires]

Originally Posted By: Torquejumper
Are you sure it's the oil? Maybe there are other factors that affect gas mileage (e.g. driving habits, quality or type of gas, weather conditions etc). In my opinion, I wouldn't contribute the 3mpg loss to the oil you're using. Based on my experiences with different oils in the Spec V, oil viscosity tend to have very little effect on gas mileage nor power. I have ran both 5w and 10w-40 synthetic on my Spec V, and I can still squeeze out 31mpg all highway driving 70mph on cruise control; that's with a header and intake.

Have you heard about the precat and butterfly screws problem on the 02-06 Ser and Ser Spec V?


Yes I'm not new to SpecVs.. mine has had all the QR25 issues taken care of before they were a problem.. mine's a a bit more modified, puts out 180hp to the wheels and ran 14.4 on the quarter mile

it's definitely fun.
I think it's the oil because I am not considering around town driving, or different fuels, or temperatures. Both MPG measurings are at 75mph with cruise control on, A/C off, same tires at same high psi, same temperatures (under 40*F), and same gas (87 from shell)

 

[dparm]

There's plenty of other good oils out there. I'd try something else and see how it hurts the mileage. Not sure what that motor is spec'd for.

 

[Vaca]

Originally Posted By: MrWideTires
I used to use edge 5w30 and then switched to their 0w20 for the winter.. Always averaged 28.4mpg on the highway going 75mph with cruise in my SpecV. Now since it has 106k miles I decided I would switch to GC and my mpg instantly dropped to 25.6mpg under same conditions.. I love GC but not when it's gonna cost me 3mpg when driving 35k a year..


Very unlikely that the fuel usage would increase such a drastic amount by changing oil. Maybe if you changed the oil in an Indy car from the ultra thin stuff they use to maybe a 20w-50, maybe, just maybe fuel usage would increase by 10%...

but changing from a 0w-20 to a 0w-30, even a thickish 0w-30, the fuel usage increase is not just from the oil.

 

[dubie2003]

As we have all read, the GC is a thick 30 (boarder line low 40) so it could have this type of impact. I have read people complaining that they dropped 4mpg when switching from a 5w30 to a 5w40.

A simple check would be to drain the GC and replace with EDGE 5w20/30 (whichever you feel comfortable with) but make sure you save the GC. If you mpg stays the same, it is probably an environment issue (winter blend gas or climate) and you can use the GC on your next change. If it goes right back up, then decide if you want to use the GC and take the hit or put it in your lawnmower, lol.

 

[Torquejumper]

Although this is disputable, I have heard that running 87 in the Spec V as oppose to the recommended (not require) 91+ octane could give you worst gas mileage or vice versa. Some say 89 is best for fuel economy. I don't know what to believe, but I have recently ran 87 in my car also and there was no difference in gas mileage. The only thing I noticed from time to time was that my timing was being retarded during hard low end acceleration. There was a lack of power. Otherwise than that, once it hit higher rpm it was impossible to tell.

I run 91 in mine because I have the 03. The knock sensor is better on the 04+.

You're at 106k. New spark plugs? Not sure if this is true or not, but I have once heard from a dynojet tuner that running 87 on a car that recommends or require 91+ could foul out the o2 sensors and cause premature cat failure. But I also heard the opposite lol.

The thing about gas mileage and the type of oil used is that it's hard to make a solid conclusion about the effect of oil and its viscosity on mpg. Usually if I see consistent 3mpg loss on my car, I attribute it to some type of mechanical defect. Maybe you should run that oil for 2-3 more oci before confirming your conclusion?

When I first got my Spec V, I ran nothing but 5w/10w-30 synthetic in it. Recorded its gas mileage for both city and highway for thousands of miles. Switched to a 5w/10w-40 synthetic due to oil consumption and monitored the gas mileage over a couple oci to present. The difference in mpg between both oils was anywhere between .3-.5. But if you considered the margin of errors and other variables, I'll say it didn't make a difference in mpg in my case.

 

[MrWideTires]

Originally Posted By: Torquejumper
Although this is disputable, I have heard that running 87 in the Spec V as oppose to the recommended (not require) 91+ octane could give you worst gas mileage or vice versa. Some say 89 is best for fuel economy. I don't know what to believe, but I have recently ran 87 in my car also and there was no difference in gas mileage. The only thing I noticed from time to time was that my timing was being retarded during hard low end acceleration. Otherwise than that, once it hit higher rpm it was impossible to tell.

I run 91 in mine because I have the 03. The knock sensor is better on the 04+.

You're at 106k. New spark plugs? Not sure if this is true or not, but I have once heard from a dynojet tuner that running 87 on a car that recommends or require 91+ could foul out the o2 sensors and cause premature cat failure. But I also heard the opposite lol.



Yeah many members in b15sentra flamed the heck out of me for running 87, but I haven't seen any difference between 87 and 93, that 14.4 second quarter mile was with 87 so I can't be hurting it.

It's not spark plugs.. I changed them 5k miles ago, they are iridium one step colder. And can't be the cat because I don't have any.. lol.

 

[dparm]

You should be running what the manufacturer recommends. Nissan isn't stupid, and they certainly don't specify 91+ if the car runs the same on 87. I'm betting your knock sensors are pulling the timing.

 

[MrWideTires]

Originally Posted By: dparm
You should be running what the manufacturer recommends. Nissan isn't stupid, and they certainly don't specify 91+ if the car runs the same on 87. I'm betting your knock sensors are pulling the timing.


It's the same engine that's in the Altima, and it recommends 87 in the Altima.

I tested my MPG on both fuels several times, did not change the slightest bit.

If the timing was retarded, it would not be putting down the power it is putting down, or running as cool as it does.

 

[Torquejumper]

True lol. I once saw a post somewhere on the net where a guy used 83 (don't know if this was a typo) on his Spec V and ran 14.4 as opposed to 14.2 (on 93).

I wouldn't hesitate to use 87 all the time if I had the 04+. But I still run 87 in my car from time to time when gas prices are high.

On the contrary, I've read on the forum that some dude ran 89 on his Spec V with the knock sensor relocation mod, and his car started knocking. The conclusion the op made was that if the car knocked with 89, it will knock with 87; therefore you should always run 91+ because this demonstrates that timing is being retarded with the knock sensor in place. That got me thinking, but I don't know if this is valid or not.

 

[Torquejumper]

Originally Posted By: MrWideTires
Originally Posted By: dparm
You should be running what the manufacturer recommends. Nissan isn't stupid, and they certainly don't specify 91+ if the car runs the same on 87. I'm betting your knock sensors are pulling the timing.


It's the same engine that's in the Altima, and it recommends 87 in the Altima.

I tested my MPG on both fuels several times, did not change the slightest bit.

If the timing was retarded, it would not be putting down the power it is putting down, or running as cool as it does.


I know Nissan knows what they are doing but after coming across and reading some many horror stories with the QR25DE motor (excluding the new Spec V), I'm kind of skeptical. I've never seen so many low mileage motors replaced because of precat failures and butterfly screws coming loose and scoring cylinder walls.

Poor crank sensor, head gasket, and piston ring design were some of the other common problems.

I don't think using 87 in a car that recommends (not require) 91+ is a problem. If I recalled correctly, the manual stated something to the extend that using 87 in the 1.8-2.5L Sentra was acceptable. Use 91+ for better performance. Said the same thing in my gf's 98 Maxima GLE which specs for 87.

Don't you think "better performance" is a rather vague term especially in a car that has a 9:5:1 compression?

 

[dparm]

All of our Nissans say the same thing. My Acura and my Honda did too. My Audi also says that you can run <91 octane too. I wouldn't do it long term, but we're getting off-topic here.

 

[Torquejumper]

Originally Posted By: dparm
All of our Nissans say the same thing. My Acura and my Honda did too. My Audi also says that you can run div>


Yeah. Anyways, I highly doubt the op's 3mpg loss is oil related. I'm currently running Rotetlla T6 5w-40 in the same motor, and my mpg is the same as factory spec if not better.

 

[nitehawk55]

I'll bet it's cooler morning starts and does FL get winter gas too ? I'm sure you don't need it but I'm betting refineries don't make special batches of summer fuel just for the southern states . If so that will effect milage too .

Just a thought .

 

[ChiTDI]

Originally Posted By: MrWideTires
I love GC but not when it's gonna cost me 3mpg when driving 35k a year..

I found GC to effect city driving much more dramatically than hiway. Save the GC for your interstate time.

 

[Capa]

Several posters that have used GC 0w30 have reported a loss in MPG. The OP loss is quite significant and may be a combination of the thicker oil and winter fuel. Yesterday in my vehicle I measured the worst gas mileage since I've owned it---same oil, gas station, etc.

 

[hate2work]

If you really want to know, simply remove the GC and replace with the Edge you were running. That would immediately give you the answer as to whether or not it was the oil.

From everything you've said, it sounds to me like the oil is the cause. I tried GC in my 4 cyl Tacoma, and it gave me sluggish starts on colder mornings, so I know it can have an impact.