70% of my driving is on the freeway at ~65-75MPH and I get about 21-23MPG on average. I'm sure any properly maintained G35 could get 25-28MPG if they do ~60MPH and/or just don't drive aggressively at all.

The G is basically a 4-seater 350Z that's a little heavier and quieter, so yeah many of the parts are interchangeable. As much as I'd love to see another G being in the hands of someone who isn't an inexperienced high schooler, to be honest with you, the Si would be a better all-around car as far as practicality, fuel efficiency, and sportiness go. I drive my car pretty aggressively and I get about ~330miles to the tank with the 75MPH freeway driving (not drafting behind semis) and city driving (60% of the time).

I've heard of some getting as little as 11-14MPG and they've said their cars checked out at multiple mechanics, so I don't know what the deal is there.

I would assume that both cars are equally as fun if you're just doing city driving with the occasional back road runs. However, all of my suggestions (leaning towards the Si) are based on what you're saying the car is going to be used for. My G35 = ~330/~17.5 gallons filled.

Hope that helps. My class break's over now lol. Good luck with your decision making man. Maybe also visit the tech and FAQ sections; that should answer a lot of other questions that you might have.

 

G all the way....

 

Op, I have a sedan with 164k miles, 160 mile round trip commute since new in 05. Only maintenance has been fluid changes, plugs, belts, brakes and compression rod bushings. I currently need sway bar end links and brakes again. There have been several on here that have 200k and counting with only the above maintenance. I don't know about 500k, but time will tell.

 

I'm surely not expecting 500k ha but 200k range is always good to see.

My biggest problem with looking for 35s is there's very few 6 speeds. Plus then it has to clear my standards of condition and ect.

 

^ I was the same way. There are so few 6MTs for sale, especially at the dealership. And all of the ones you find on Craigslist are either auto or beat up 6MTs with high-ish miles, at least the ones here. Don't settle, keep looking, and the right one will find its way to you. Unless you have the $$ then just settle and fix it up. =D The autos aren't bad. Sometimes I wish I had a 5AT. Sometimes.

 

The AT's lose their luster as you're looking at high output mods... but I still think that I spend 95% on the street and 5% of the time getting on it. 95% of the time I'm happy I have an AT while 5% of the time I wish I had that more robust tranny with a clutch I could upgrade for less than 5k.

Not to turn this into an MT vs AT discussion- I still think given the IP that the civic is the more appropriate option.

 

G's aren't high maintenance but will be higher than a civic. Comparing a G to a civic to me is a no brainer, but then again I value comfort and options and luxury and rwd more than good MPG's so I LOVE my G. But it sounds like the OP wants an economy car not a luxury sports coupe, so go with the civic.

 

You can't compare his mpg to yours..there too many variables. Such as driving style, maintaince, mods, what size rims, what brand tires, whats the psi of your tires, location, elevation, air temp. You get my drift.

There some turbo guys getting 26mpg on the high way.

I've gotten 29mpg driving from Los Angeles to San jose (400 miles one way) in 100 degree heat with the AC running. I was driving around 75mph in 6th gear, at around 3k rpm.

I average about 24-26mpg on the free way and 17-19mpg in the city I average around 22-24mpg combined.

To the OP you can basically get the epa numbers if you drive civilized.

 

Sounds like your looking more for economy, i would just go with the si.

I would also suggest looking at a 06 rsx type S. There cheaper, same motor and comes with leather and its also a hatch back so you have more utility.

 

I don't want to be a dick, but you posted two completely opposing statements.

I drive I would say 60-70% freeway, 30-40% around town and average 20-22mpg. I would say I drive somewhat aggressively.

OP: A G35 isn't too crazy to maintain if you do all the work yourself, but the SI is cheaper to maintain.

Assuming the G35 is within your budget I'd opt for it. Yes, your mileage will be slightly worse, but it's a more comfortable highway car, I'd say. Probably more rewarding in terms of being RWD.

 

It's not really that unheard of my man. You want the picture I have of pulling 31.5 mpg after a reset and 15 minutes on the highway at 65? This is off the OEM nav. I would routinely pull ~27.0 mpg at 75-80 mph and up to ~28.3 if I drove a bit slower. I would take the trip every weekend and reset the nav mpg once I hit the 90 mile stretch of freeway. I would be happy to give you a video or more pics if my car was functioning properly...

Intake mods were:
MREV2
5/16th Spacer
Aramid Gasket
Chaos Engineering Throttle Body Spacer
Z-Tube
Stock exhaust
Amsoil 5W-30

I put my TDX2 on and noticed a drop to 25, but it's hard to tell if that was due the problem(Suspected VTC pulley) or the exhaust since they both happened around the same time. This is in a 6MT as well so I'd be at a lower RPM than a 5AT(I think). I was still only burning only under 1/5th a tank of gas on a 95 mile trip.

 

I'm coming off sounding like I'm wanting economical as I'm about disgusted of 14 mpg with my current vehicle and I want to be sure I know what I'd be getting myself into with a G35. These latest comments have been encouraging.

Like I said before I'd be very pleased if I could pull 24-25 highway when driving conservatively (cruise at 70 or so).

 

My bad Revo, I'm just giving guesstimations based on my real-world driving scenarios. But ultimately he should get what I mean. I'm sure elevation, gas quality, etc will affect your MPG range, but I'm just saying that I don't really baby y car, I accelerate quicker than most from a stop, and I drive above the speed limit and what the EPA ratings are and those are the numbers that I'm getting with absolutely no mods done to my car and probably even low-ish tire pressure due to the cold NW weather here. Hope that helps OP.

 

The stock exhaust, I admit, sounds pretty awesome- but only if you're wailing on it all the time. If you like the sound- then you get crappy MPG. If you're used to it... you CAN get good MPG. I couldn't even conceive of getting mileage described in this thread... but hey- if it's possible, it's possible!

At the same time, it seems to me "possible" and "practical" don't exactly go hand in hand in this scenario. If you want to drive like you have a glass of nitroglycerine sitting in the passenger seat- then power to you but then there'd be NO sense buying a G. I know I'm a BIT harsh about the performance... but though it has some snap to it... it's just not enough to justify sacrificing the opportunity to get a car that is better suited for you overall.

 

The G is the more fun car. The Civic is the more economical car. It's really as simple as that. I don't consider the G a "luxury" car. It's just a 350Z with back seats. LOL. Well, to me it is. That said, I love mine and am extremely happy with the purchase.