I drive streets around 40MPH to 50MPH and getting consitent 18.5 to a gallon.

This week I drove probably 40 miles freeway plus the rest street, but I was aggressive n the streets and I got 17.8.

I think it is safe to say that:

City Driving..normal and smooth driving style would be 17-19 to a gallon

Freeway - normal driving, smooth following speed limit 65mph here in L.A. would be 20-24...

hey what can you do.... we have this kind of engine...

 

AGREED! 100% (Thank You)

Anything else is really not relevant. Furthermore, and although this would probably complicate it for the simpletons, as a check, it would be interesting to have the average mph reported along with the mpg; as it's unlikely you'll get high mpg without a fairly high average mph too.

 

I managed to get 27 mpg, while doing 70-75 cruise control with A/C
one thing my buddy told me is that your car being clean helps alot too on long trips

 

20mpg no matter what. I've tried to baby it to no successful increase, so I dont even bother.

 

is best to try it when you have a fresh oil change,and make sure all tires r at 38 psi.
When i drive far i put lucas fuel system cleaner in my gas tank.
what kinda gas?tell me it wasnt arco

 

This was a topped off tank for my 5 hr trip to SC, I am returning tomorrow to Ga and will do the same on the way back with the same gas. Military base 93, from AAFES for those familiar with the Military. It's no special gas and i don't know who provides it. Guys this is all highway miles with about 7-10 miles city driving to get to the interstate.

My city driving around the Military base on which I live is a constant 17.2, which isn't bad for a car rated 18/25 city/hwy

 

My average speed is in the mid 40's. On my fill up this morning my average was 46mph with 20.9mpg on the dash. I reset my trip computer every time I fill up and I also reset the average and instantaneous readings on both displays. When you look at the history of my MPG is it almost a straight line. I also average about 360miles out of a tank of gas.

 

how many miles does your car usually say when you all fill up?

 

I pray to see 20mpg!!! but I am averaging about 17mpg.

 

That depends on the type of driving you're doing. The computer will read to reflect the type of driving, here why:

Normally when driving around my base, and i stop to top off my computer usually says 320 mile range.

After i got to SC yesterday I topped off at the base here and it said like 587 (cant recall exact display) range. But that's because I've been driving highway miles for 5 hrs straight with no stops and maybe 5 braking/slowing.

 

I got 26.8 on this tank. I was doing better until I was stuck in traffic one day and another day running late to work and therefore haulin a$$. I drive mostly highway. Go over 63mph and it goes south quickly. I fill up more than one a week at Sam's Club.

 

+1 on the full tank of gas... otherwise I can honestly say the most my mpg lcd has ever read is 73 mpg...

 

I did 3 test cruising on highway at various RPM (2400, 2600, 2800, and 3000) and found that at 2600rpm, I got highest mpg ~ 28.

 

Couple things to note about fuel mileage on G35:
1. you need to specify if you drive 6MT or auto. Because it is easier to get better mileage with 6MT especially in town.
2. Gearing on these cars is rediculously short so for sure going slower will help a lot. Someone mentioned 63MPH or less. I am sure that would yield better MPH but where I live, you get killed on fwy for driing that slow! My car at 76mph, engine spins at 3000rpm so for sure it is sucking down more fuel than it needs to.
3. I usually have my AC off. I usually drive early morning, late evenings. I use it when it is really hot out. In evening, I like to crack the windows and enjoy the breeze. I have not noticed that turning AC of affects fuel economy that much. I think G35 consumes more fuel than it should regardless of how easy you drive, with or without AC. I say this based on several other cars I have owned.
4. Fuel economy is always worse in winter if you live in cold climate, like 2-3mpg worse than in summer.

I have 6MT. Best I get is 24.5 fwy (at 70-75mph) and city driving mixed. I always check my mileage per tank by checking miles on trip meter versus gallons pumped. I find both trip computers are a bit optimistic most of the times (one in center stack and one in center of gauge cluster). I have never driven fwy for full tank of gas. I did notice once after filling up, resetting computer and driving fwy home, I was getting 26.8-27.0, with a slight tail wind at about 70-75mph. But rest of that tank was consumed driving around town. On average, I drive 90% surface streets, not fwy I get 21.5-22.5mpg in summer time. If I try, I can get 23.4. Fuel economy drops easy 2-3mpg in cold winter weather

I would say if you are getting 27mpg, that is about as good as it gets with 07-08 G35 6MT.

 

Just filled up after my drive home from Austin. Only needed a half tank and had done about 15 miles of city driving, but was real curious to see what I got.

24.5

Some of the driving was backroads where I could only go about 65....some of it was checking out what she had on the open highway.

Read a thread where a guy got 27 after installing intakes.