Hey guys and fellow M45 owners .. just wondering how your gas mileage has been on the M ...

Now that I'm close to the 3000 mile mark, it seems to be getting a LITTLE bit better. I can usually get around 300-350 miles to a tank (before I have to fill up again and the gas light comes on) -- By the way, after the light comes on, I usually fill up, and it will only take 17-17.5 gallons, meaning there's still almost FOUR gallons left in the tank - this leads me to believe I can probably squeeze between 350-375 miles out of an almost full tank.

I've noticed that after I fill up, I'll get close to around 50-75 miles before the needle even dips below the 'F', and then it seems to fall rapidly. Have you ever noticed how between 3/4 full and 1/2 tank that if you REALLY floor it on the highway, or take some steep curves, you can actually WATCH the needle drop ?! Boy, this car really CAN be thirsty -- but the exhiliration is worth it !!!

The other day on the highway, RIGHT after a fill-up I reset the Fuel Economy computer and actually (for about 2 minutes anyway) was averaging 28.2 MPG -- well, of course it didn't last long, as I started punching it, and it settled on around 22 MPG for the rest of the trip - which I guess is OK for highway driving. But, in the city, I still can't seem to manage better than around 18 MPG !!!

Oh well -- sorry for the long post !!! Hope everyone is enjoying their M like I am !!!

I'm sure am enjoying my M! I have to restrain myself from punching it too much... At 3500 miles it's getting 20 in the city and 23 highway. It sure does drop way fast after the F. It must be a Nissan/Infiniti quirks since all of my previous cars have done the same.

I get about 16-17 mpg on average at the moment. About 70% highway and 30% slower roads. When my wife uses it, she does not go on the highway, so the mileage tends to drop into the 14-15 mpg range. On longer segments (like when I drove to San Francisco and back, so the highway use was more than 90% for that tankful), the average was closer to 22-23 mpg.

Z

Every gas gauge will be slightly different since the exact bending of the float arm varies with WHO and How they installed the assembly.

Same with the seperate low fuel sensor a 1/100 of an inch error is a lot when you think of the surface area of the tank bottom.

Every time I change my fuel pumps the arm gets bent slightly and the gauges changes some.

Allowing the fuel to get below say 5 gallons does cummlative damage to the fuel pump.......takes miles off its life.

Don't be complaining at 71k-100-120k when you have to change the pump............you will have contributed to its failure.

The EPA [quasi-RURAL] city mileage is 17 and rural not to exceed 60 mph highway mileage [no high speed passing allowed] is 23 mpg.

A 4.5 liter engine gulps a very well known and exact amount of fuel for every revolution............keep those rpms down and as low as possible to maximize mpg.

Well ,I have the M for 2 weeks now . 2 tankfulls in city driving I got 14-14.5 MPG , which is exactly the same as my 91Q does . However I drive the M much more agressively , just can't leave this sweet motor alone . The fuel computer said 23MPH average speed for those 2 city cycles . One semi-highway trip from N.J. back home when I bought the car , she returned 23MPG .

Q45tech wrote:Allowing the fuel to get below say 5 gallons does cummlative damage to the fuel pump.......takes miles off its life.

Don't be complaining at 71k-100-120k when you have to change the pump............you will have contributed to its failure.

............

A 4.5 liter engine gulps a very well known and exact amount of fuel for every revolution............keep those rpms down and as low as possible to maximize mpg.

Yep. I fill up when the gauge gets to 1/4. Never understood the challenge of running the damn thing near dry.

...............

It is true that she drinks less doing the lazy turns. However, she only sings in the upper register, and what an intoxicating song it is. I must confess that I like to hear it often.

Russ

23 hwy mpg is a great milage for a V8 sedan.

Fred...

dezm45 wrote: I can usually get around 300-350 miles to a tank (before I have to fill up again and the gas light comes on) -- By the way, after the light comes on, I usually fill up...

If the fuel pump design is like the G50 Q45 (any bets?), it's life may be enhanced by filling at the 1/4 tank remaining mark rather than letting it suck continually to the bottom of the tank.

" 2 tankfulls in city driving I got 14-14.5 MPG , which is exactly the same as my 91Q does "

Why would you expect differences, same size motor roughly the same gearing, and only a few hundred pounds differences in weight..........and only 0.5 [rounded up to 1.0] improvement in highway EPA numbers.

Everybody wants a 5.6 liter engine till they learn about the 20% decrease in mpg..........most don't learn till after they buy.

Nothing sucks gas like displacement.

My 97' gas gauge is EXACTLY the same, although it drops faster but takes a big hit in the middle. I get about the same as you do, but when I drive to LA I can get over 350 miles on the tank and still end up with 4 gallons left. The gauge is very conservative....btw, my wife drives like a little old lady and the one week she drove the car it got 24mpg...I just think if you have a V8 how can you not nail it every once in a while, gas milage be damned.

But I can still remember my dad's old Caddy's and Station Wagons that got 8-10mpg so when you think about even getting somewhere near 20 in a V8 that is amazing.

A 4.5 liter V6 would get the same mileage ,[maybe worst] than a 4.5 liter V8 or a 4.5 liter V10-V12.

Displacement, bore, and rpm...........why in Asia and Europe your car is taxed on displacement in addition to the high prices of fuel.

Much easier [honest/accurate] than the CAFE mumbo jumbo.