This is my first time posting on this forum. I just recently got a 2013 G37x from a family member and so far I love it! My biggest concern before getting the car is the fuel mileage and needing to put in premium.

During my first two fill-ups I reset Trip A and the MPG counter to zero and calculated the mileage using the old fashioned way to compare what the computer says:

Trip 1
Computer says: 24.2 MPG
Calculator: 22 MPG

Trip 2:
Computer says: 23.7
Calculator 20 MPG

The second one bummed me out a bit. I don't really have a lead foot and I was trying to see how high I could get this thing with mostly city driving.

So my question is, have other people seen more accurate numbers (comparing computer vs. calculator method)? Am I being too picky about the computer being off 2-3 MPG? Are there ways to get the computer to be more accurate?

 

City driving kills fuel mileage. 20 mpg city is great in my opinion.

The computer is never going to be 100% accurate. It is only doing calculations based on throttle input, load, etc. I don't have a G, but on my Grand Prix it is never accurate either.

One time on a road trip it told me I got ~25 mpg, but once I filled up and did the math I actually got over 28 mpg, and that was after several short trips to town for supplies before I actually filled up. Had I filled up before all the short trips I probably would have been closer to 30 mpg and the info center would have only said high 26 at that time.

If you are concerned about putting premium in then you bought the wrong car. Point blank, period put premium fuel in the car. Do the math, its usually only about $6 more a fill up on 87 versus 93 (or 91 if that is all your area has) and you are not going to get knock which pulls timing which hurts fuel mileage. In the end you save nothing by putting in regular over premium.

 

I would never put in regular just to save a few bucks. That wasn't the point here. I thought i read from other posts about how the computer was off only by like .5 MPG compared to the calculator. I was just curious if being off 2-3 is considered normal.

 

The computer is never accurate so don't worry too much about it. I hope you knew that this car with the big v6, awd and the weight its lugging around would have terrible mpg as expected compared to recent standards. Also most car's mpg usually suffer during ownership. Our Computer monitors mpg based on how hard you drive or how much traffic your in so its constantly changing. There are a lot of other external factors that also affect the mpg that the computer doesn't take into consideration. You can baby the car and get 20 mpg but take a hard turn and mpg can drop to 10.

Pro tip for better mpg is to throw into manual and shift early to the highest gear possible while keeping rpms below 2,000 rpm (driving light footed). For example, when you're own the highway doing 50-60, the automatic transmission might keep the car in 5-6 gear but manually throwing it into 7th will lower the rpm to around 2 and improve mpg.

 

I drive in manual all the time. Besides the same, if not better gas mileage than the ECU/TCU can do, the car won't downshift to fifth on the freeway going up overpasses with cruise control on. That's the ONLY time the car downshifts with little urging when in ""D".

 

In my experience the computer generated MPG isn't that accurate, just kind of close on this car. There isn't anything to do to make it more accurate, at least not that I'm aware of. The old total miles driven/total gallons consumed is the way to go. 20-22 MPG isn't bad for average driving in this car. EPA mileage numbers are complete garbage and shouldn't be your point of reference.

Inbeforecaptainhypermilerchimesinandtellsyouhegets 30mpgusing87octaneandhasonhislast3carswithreceipts fromeveryfilluptoproveit

 

my computer MPG isn't 100% accurate, but it's close. usually +/- 1MPG, often less. so i'd call that good enough for the casual observer. anyone who cares for more exact readings need only perform a 3rd grade calculation.

 

I've tracked my mileage since I bought my G last fall, using the gauge in the car (reset at purchase) and an excel spreadsheet (actual miles & gallons for each fill up). The OEM gauge is within 0.4 miles per gallon so far after 10k-ish miles. YMMV.

 

The fact is the computer is very accurate, but our calculations are not.
The car calculates MPG using the ABS wheel speed and the "fuel consumption" line (injector pulse width), so it knows EXACTLY how much gas as been consumed and the distance.

When we fill the tank, it is never filled to the EXACT same level and we assume all the gas we put into the tank is used, which throws off our manual calculations.

If you track the milage and fuel used over a longer time (a few thousand miles) you will see the calculations average out to be more accurate and closer the computer.

My average over the last 7500 miles is 21 MPG, 80% city.

 

Telcoman

 

You da man! I know you couldn't resist the siren call of a fuel mileage thread. You're kind of like our forum's very own MPG Rain Man.

I dare you to redline your car. Just once!

 

Dooo ittttttttt!!!


On a side note, I was pretty far out of town and needed gas so I filled up with 91 and I swear the car felt more peppy and shifted better, how nuts am I?

 

^ lol. here we go...

 

As nuts as Donald Trump

 

Why?
What does that prove?

I've proved to myself since December 2005 when I purchased my 06 G35 6sp manual that the required/recommended use of anything mentioned in the owners manual other than 87 octane is not only a myth but a waste of money. I don't care what amount of HP is reaching my rear wheels.
A new vehicle purchased at the dealer comes with a full tank of regular.
In over eleven years on a number of these forums I've never read a post where the member that purchased a new vehicle with a full tank of gas actually sent a sample to a lab for a test.
I have read posts of members sending out oil samples to a lab but never the gasoline that the dealer delivered in a new vehicle.

The vehicle computer mileage graph is a round trip from NJ to Florida that is reset after every fill-up.
The fourth fill-up where the mileage dropped is the result of a brief shutdown of I 95 and heavy traffic due to an accident
The next two graphs show drops in MPG for local driving in Florida.
The last four fill-ups are the return trip back to NJ.

BTW this road trip was made with two grandchildren under the age of five.
It may be difficult for some younger members to understand that when driving with young children they notice everything and ask lots of questions.
I observe many drivers accelerating sharply from a traffic light only to have to slam on their brakes at the next light. I guess some of those then complain of poor MPG, excessive wear on brake pads,tires and warped rotors.
Infiniti gets great MPG on long road trips
Infiniti gets not so great MPG on short trips, heavy traffic, and abusive driving.

BTW I never use cruise control and keep my tires inflated to 35lbs

Telcoman