Anyone else here get between 13-14mpg? I have a 2010 g37x coupe and I currently have stock OEM intakes, FI exhaust, BBK, and Vossen CV3s if that makes any difference. I had R2C intakes before and thought it might be the cause for the low MPG but it did t make any difference. I had my spark plugs changed, throttle body cleaning, reset my ecu, dealership updated the system, and new filters. I currently have 44,000 miles on there but this has been a problem since I bought the car 4 years ago. It also lags so much and don't know what to do anymore except getting rid of it. Any input would help!

 

The majority of the time that someone gets horrible MPG compared to what the car is typically capable of, the issue is how it's being driven. A lighter right foot might be the answer. There could be something actually wrong with the car but most of the time there isn't.

Try driving it in the most fuel conscious way you possibly can for several days and see what your results are. Also, make certain you're calculating fuel mileage accurately and not simply relying on the computers calculation which is often inaccurate.

 

Is this mostly city or highway mixed too? How much are you stopping? Are you accelerating quickly after say after a stop sign or light? I have the same model car with Niche 20s, Takeda long tube, FI HFC, decals and Top Speed Axleback (Soon to be Ark Catback) and according to the cars MPG I do 19 city/highway mixed. I mostly do city rather than highway also. I haul on highways and do atleast 10 mph above speed limit in city depending on traffic and its GA so dealing with 100+ temperature.

 

I used to be in the 13-14 area with my '11 xCoupe too and was rather annoyed. I haven't really lightened up on the gas but I do mostly take it on the highway now and I'm averaging 17.4 - some tanks as high as 19. Also this is not from the computer but from recording my mileage and fuel added every time I fill up

 

I haven't had this car for long but generally speaking, I agree with the above statements that its most likely environmental than the car itself even if you don't have a heavy right foot.

I've seen with other cars I've had when I was living in a city to be nowhere near stated city gas mileage. Other times, it would be near or higher than the stated highway miles when I lived in the boonies. Also, you need to really spend at least 20 minutes on the highway at cruising speed daily to approach the listed highway mileage as well. So all in all, 13-14 living in urban MD wouldn't be all that out of the question imo. Probably not the answer you were looking for but hope it eases that nagging thought something's wrong with your whip.

 

AWD is a big cause of crappy gas mileage, so is the A/C if you're using that. Do some research on hypermiling, some of the tips might help you to squeak more mpg out. I did this when i got my daily driver last year. I was only getting around 21-22 when i figured it had to be closer to 25 so i put extra effort into getting better mileage and i hit the numbers i expected. It was way too much work to get a few extra mpg though, but at least i knew it was my driving vs an issue.

 

This is mainly city driving and I also need to step on it harder than other vehicles because the car lags so much and slow at accelerating. When I press on the gas pedal it makes a lot of noise first then 2 seconds later it would move. Hondas and Toyotas even beats my car from a red light except my car is louder. I had a loaner g37 several times and they run much better than mine.

 

I've been looking into the Ark Design Throttle Controller which helps with throttle lag. Maybe get a tune which could help also? But if it's mostly city miles with barely highway than I can see why the mpg could be low.

 

I have a '13xs w/32,000 miles. My mpg is entirely dependent on driving habits. Generally I drive around the suburbs and about 15 mi commute to work and I avg about 20-21mpg. Highway I easily get 27-28+. If I put it in DS and use the paddles to shift I have a habit of hanging out in the lower gears and my driving style is more "spirited" and my mpg goes down into the teens...

Perhaps you might pull one of your new plugs and take a look, they can give you an indication if your running too rich or too lean. Then you can further assess the problem from there. You mentioned you already replaced the plugs once, how did they look? 44k is still pretty early for new plugs...

 

I wouldn't suggest hypermiling (following another car/truck to decrease drag) to anyone. It's a dangerous habit and also causes your paint to get sprayed with rock chips. It was a big thing, especially among drivers of hybrid cars, but in retrospect there is little reward for accepting the risk of crashing

 

I am noticing worse mileage than I was before too. For me...I think it might be the extra rubber on my wheels. When I got new wheels I went 255 all around so that is more surface area. But I noticed my mixed average wen from 23-23.5 down to 21-22.1...same driving habits same driving conditions.

 

I get about 19 around town in my m37x which is heavier .... driving habits make a BIG difference!

 

Thanks for pointing this out. Another reason to stick to stock tire sizes unless you're actually driving in a manner where it's beneficial to have wider tires (ie tracking the car).

 

This is why you have crappy mileage.

 

Sorry, hypermiling is the practice of forcing as much efficiency out of your car mpg wise as you can. What you're referring to is drafting or tailgating and is of course a very dangerous practice. Hypermiling involves things like over inflating your tires to reduce drag on the tires or holding your gas pedal in position going up hills to keep fuel consumption constant while speed decreases.