Poor Gas Mileage - 05 G35 Sports Coupe

[lomita]

Am getting 11.5-12.5 mpg city with automatic transmission. Normal driving, not hot rodding.

Vehicle has 20,000 miles.

Replaced airfilter with K&N drop in.

What should I try next? i.e., plugs, wires, coils, O2 sensors, MAF, etc.

Any subject matter experts out there can lead us down the path?

Thanks.

[rn79870]

Welcome to the forum.

Gas mileage has been a topic discussed here quite a bit. G's are not the most economical cars, but you are experiencing poorer than normal mileage. I typically get 16.5+/- in town. Some of it may be how hard you accelerate too, I drive relatively easy 95% of the time.

Have you checked for any obstructions in your exhaust, like a bent-in pipe?

I doubt at 20k new plugs or wires will help much.

You might do a search (the big flashing button at the top of the page) for threads on fuel economy in both the G35 (this) forum and the G37 forum.

Others will be along soon to check in on this pretty soon. Welcome again.

[lomita]

Will check for exhaust restrictions; don't suspect we'll find any.

[telcoman]

Am getting 11.5-12.5 mpg city with automatic transmission. Normal driving, not hot rodding.

Vehicle has 20,000 miles.

Replaced airfilter with K&N drop in.

What should I try next? i.e., plugs, wires, coils, O2 sensors, MAF, etc.

Any subject matter experts out there can lead us down the path?

Thanks.

lomita:

Welcome to NICo

I don't think what you are experiencing is all that unusual if most of your driving is short trips in heavy traffic. How about on a 300+ mile trip?I just retuned from a round trip from New Jersey to Florida and got close to 28MPG on a couple of tankfuls at a steady 75-80 MPH. Although the 6 speed manuals get a few extra MPG I'd be curious to know what kind of MPG you get on a long open road trip? My tach is exactly at 3k rpm at 80 MPH. When I drove an automatic loaner the tach was around 3300 RPM at 80 MPH. That accounts for some of the difference.You could always use the George Bush rebate money to trade it for a 6 speed manual. Our economy is sinking

Could also be californication?

Telcoman

[Q45tech]

An ideal economy rpm for 60 mph is 1800-2000 rpm and 2400-2666 rpm for 80 mph. V6 don't produce enough torque at low rpms so they usually turn 10-15% higher rpm than the bottom numbers.

Unfortunately to beat competition and still use in stock 5AT gear ratios without a redesign Nissan chose a high ratio diff.

So fuel economywise a 3.5 V6 acts like a 4.0 liter V8 consumptionwise.

For 18 years Nissan hung in there with the ideal compromise V6 at 3.0 liters but the magazine HP wars forced the 3.5>3.7 dispacement upgrade.

A high rev 24 valve V6 will be less efficient at low rpm than a US old school GM/Furd V6 with 12 valves -------------------often by 10% or more.

[lomita]

Speaking with local G35 owners, they mention they are getting 16-18 mpg here in town. Our vehicle should be able to get like mileage as well if all components are functioning up to par.

Ordered a set of Nippon Denso Iridium plugs and threw half a can of Seafoam in the induction this afternoon. Runs smoother already. Will post additional results after the plug change.

[Bullet_35mm]

It is a little bit TOOO LOW !!! Your car is on the factory warranty, I would suggest going to Infiniti service and ask them what's going on, because something is not right. I've got exactly same car, same year, higher milage and my average is arround 17MPG.

[lomita]

Oil seals are leaking somewhat on the spark plug tubes, entire valve covers have to be replaced. Plugs arrived, will install, dealer to replace valve covers under warranty and then can check for mpg changes. Hope for the best!

[telcoman]

Oil seals are leaking somewhat on the spark plug tubes, entire valve covers have to be replaced. Plugs arrived, will install, dealer to replace valve covers under warranty and then can check for mpg changes. Hope for the best!

If that doesn't work, you may have to get rid of 2 wheels http://www.1010wins.com/AUDIO-...49739

Telcoman