Kelson

Hi everyone,

I have a new automatic '07 350z roadster and I am getting horrid MPG (about 16-18 MPG most of the time, even on highways). In an attempt to bump it up a bit, I'm going to try a few things, but I wanted to get some advice from you more experienced folks as to what the best contributions (bang for your buck) are.

Here's what I've done so far:

Switch to premium (91 octane) fuel. This helped for about half a tank. it bumped me from about 16-18 MPG to about 21-22 MPG for the first half of the first tank of premium fuel. Then it went right back down to the normal 16-18 MPG range.

Keep air pressure up at 35 PSI. I am looking into using Nitrogen in my tires, but from what I've read here on the forums, there's much debate about whether that will have any real effect anyway. If I can get it cheap, I might give it a shot (I'm desperate for better MPG!), but other wise, I'll pass.

Keep RPM below 3k. I read here on the forums that keeping the RPM below 3k will have a beneficial effect on MPG. I've just started paying attention to this, so I'll need to do it for awhile before I can see if it helps me.

What I plan to do:

Replace all the fluids and filters in the car with new, clean stuff. My car's still using what the factory put in it (presumably awhile ago since it was still on the lot new and is an '07 model). I'm hoping this will have a big impact.

Upgrade fluids to better versions, where able. I have a friend who works for a lubrication company (yeah, I know - I still chuckle when I think about that). They have some very nice products that I plan to use (oil, fuel injector cleaner and automatic transmission fluid). I'm also hoping this will make a big difference.

So, what else do you suggest? I don't know much about cars, so feel free to spell it all out for me. I won't be offended, I promise.

Thanks for your help!
Kelson

saberphx

iTrader: (5)

Sorry, all I have done is ruin my MPG.

kurt213

iTrader: (5)

Switch to premium? What were you using? You SHOULD be using premium gas.
Any ways I'm not sure why your mpg is so low. I get 24 mpg on average, and I most definately haven't been keeping it under 3000 rpm. I have a manual though, so I'm sure that helps. You gotta ask yourself though....is it really worth it?
Obviously you should be using premium gas and should have tires inflated properly....but to keep it under 3000 rpm??? You might as well trade it in for a civic......have some fun in it. It's worth the extra 3.57 at the pump!

NickRaine78

iTrader: (4)

You gotta pay to play!

savvy

iTrader: (1)

all that extra money you are spending on fluids and whatnot will surely negate any gains you may see in MPG...and please use premium gas regardless.

cdoxp800

iTrader: (12)

I get an AVG of 27 to 30 Hwy at about 76 mph, and 22 in town.

You should also be running a MIN of 91 octane Per Nissan.

Optamix

switch to premium?!?!?!

ugh.

Kelson

Sorry, I don't come from a performance car background. I drove a Civic for 10 years prior to this, so I'm used to just using regular unleaded.

Given properly inflated tires and premium unleaded gas, what else do you all suggest I do?

Thanks!
Kelson

Kelson

I don't know. The different between my 16-18 MPG and the 25-30MPG many others are reporting on the boards adds up pretty quick. A 10MPG increase means I can drive about 150-180 miles more per fill up. If I spend a few dollars extra on a couple of additives and some nicer oil, it could pay for itself in just a couple of tanks of gas.

jimmyloose

iTrader: (22)

if you use lower octane fuel than your car is rated for your MPG will be lower.

kurt213

iTrader: (5)

Are you really THAT pressed for cash???
Getting the most bang for your buck as per gas is really a popular subject right now with gas prices so high. I'm sure if you do your research you'll be able to find a bunch of tips that will help......but really, I don't think it's worth it. If you wanted a car thats great on gas why did you buy a Z? Just drive the damn thing.... Or trade it in on a Toyota Prius lol

Kelson

Heh, no I didn't buy my Z for MPG. But from what I've seen on these forums, I'm getting pretty horrid MPG for the Z. I'm not comparing my MPG to what I got on other cars. Rather, just against what others get with their Zs. I want to take care of my Z and do what I can to make sure the low MPG isn't a symptom of something else.

A 10+ MPG difference is pretty significant, IMO.

Thanks!
Kelson

3hree5ive0ero

iTrader: (95)

You SHOULD be using the highest octane unleaded gasoline in your Z - Dallas has 93, use it.
-You SHOULD always have your tire pressures at 35psi, unless you're competition racing at appropriate tracks or strips. Nitrogen is pointless and expensive - how hard is it to check your tire pressure and air them up if needed?
-You SHOULD have the appropriate fluids (or better) and filters regardless of what car.
-Your RPM is DEPENDENT on how you want to drive. Driving with your revs under 3000 will save a little bit of gas.

Don't try to cut corners. And also, next time you fill up, see how many gallons are being pumped into your gas tank and see how many miles you drive since the last fill up. Use those 2 numbers to find your MPG, rather than trusting the computer on our cars.

I get 99.9 MPG (see pic). You can too!

savvy

iTrader: (1)

the way you drive will be the most dependent factor. Easy on the gas, shift at lower rpm's, don't let the car idle in your driveway for 10+ minutes, ect.

davidv

iTrader: (2)

I got some gasoline pills on eBay. Two pills to a tank of water. Works great.

Jekyl n Hyde

You said your car is new...how many miles on it? My mileage improved after breaking in. I have basically the same car as u and I drive it hard. I still get average of 20+ or so on the computer calculation of mpg. Actually check the mileage (miles/gallons) , you may find the computer is wrong. Mine is usuall about 1 or more mpg higher than the computer says. As everyone else said, you have to use premium fuel. Computer cuts timing and everything else to keep the engine from knocking..I am sure that would effect everything from performance to mileage.

I am sure you have but check the two airfilters...replace if necessary. Check the plugs? wires?

If that doesnt fix it...maybe you should take it in for a diagnostic check...

Kelson

Thanks for the helpful reply!
Yeah I have about 1,900 miles on the car so far. Someone told me I should wait until 5,000 miles to worry about calculating MPG because the mileage is worse while it's being broken in. So it sounds like you're on the money.

I checked both air filters and there was a snack cake wrapper trapped in one of the intakes, blocking airflow. I'm sure that was having some effect. I'm also going to switch to 93 octane or at least start using an octane booster to help as well.

Thanks!
Kelson

blazed54

iTrader: (1)

1) always use premium

2) on a car as new as yours the only fluid/filter i would change is the engine oil/filter. anything else will be a waste of money and not improve your mpg enough, if at all, in relation to the amount you'd spend replacing those fluids.

3) keep tires at 35psi and i've never heard of using nitrogen to fill the tires with.. don't see how this will benefit the car.

4) your car is still breaking in and mileage will continually get better over the next couple thousand miles.

5) find your actual gas mileage by using the methods mentioned above. and what does the meter in your car say is the avg mph and your avg mpg?
I find that usually the higher your avg mph, the higher your avg mpg will be. for my car, even at an avg 25mph, i get 20.3 mpg. 07 Z with 10k miles.

so if you're getting an avg 16-18 mpg and your avg mph isn't less than 25, then there's still room for improvement whether in your driving or the engine breaking in. if your avg mph is actually less than 25 then your mileage is actually appropriate.

6)finally, since you have an automatic, for everyday normal driving i would shift at like 3.5k to get up to speed. once you're at speed, just keep pressing up till you're in the highest gear allowed at that speed. if you're not going fast enough the auto won't allow you upshift so you can't ever damage your transmission in this manner.

try all these things but don't worry about having fun in your car. The 350Z and HR engine LOVES to be driven hard. As long as you're not redlining at every stoplight your gas mileage should be fine even with a little spirited driving everyday . gl

singh

iTrader: (2)