Gas Milage

[joetraynor]

- My J30 T does not get the best milage per gallon. What is the average milage per gallon for the J30 T. Is there any small fixes i can make to improve my MPG?

[driverdriver]

About 20-22 MPG is normal. Run only premium octane 91 or higher(I find Sunoco works the best). Using gas less than the required octane 91 results in poor mileage. If your already doing this, then change out both your 02 sensors.

[GerryO]

Does anyone know or has anyone calculated the J30 fuel consumption rate at idle (approximately 675 rpm) with the engine fully warmed up, the transmission in Drive and fully stopped with your foot on the brake?

What's the volume of fuel dispensed by an injector per squirt under the above conditions?

I get about 17 mpg around town (sitting at lots of red lights), putting very light pressure on the gas pedal (no shifts above 3K rpm), not racing from red light to red light, running 91 octane and keeping 34 psi in the tires.

Cruising on the freeway (between 65-70 mph) might it might get 22 mpg, and that's with clean EGR tubes, a new EGR valve, six new injectors and spark plugs, recently cleaned throttle bodies and MAF, new fuel filter, timing and accessory belts, water pump, and two new O2 sensors and PCV valves.

The one improvement I can make is to restore heating of the AAC valve lost by doing the throttle body coolant by-pass, in order to pull the cold idle speed down more quickly.

Not much to look forward too, eh?


Modified by GerryO at 5:53 PM 3/16/2009

[J30inthe sun]

- My J30 T does not get the best milage per gallon. What is the average milage per gallon for the J30 T. Is there any small fixes i can make to improve my MPG?

Last Christmas I drove from Ft Lauderdale to Tampa, 265 miles. I filled up the next day & calulated my mileage based on my trip odometer & gallons to fill back up full, going @ 70-75 mph the whole trip & it was @27 mpg. In 2003 I drove from Marathon FL to Tampa one a full tank, F to E with low fuel light on at the end, @380 mile but that was going on average 90 - 100 mph.

BTW @27 mpg is with 4 new Goodyear Eagle ResponsEdge tires (215/60/15) with about 1,500 miles on them set at 29 psi cold.

Recent work done & parts repaced that would affect mileage:

4 new tiresAir filterFuel filterCleaned MAFIdle air control valve cleanedNew Throttle position sensorNew OEM NGK spark plugsTiming belt kit2 bottles of Redline fuel system cleaner

[GerryO]

Last Christmas I drove from Ft Lauderdale to Tampa, 265 miles. I filled up the next day & calulated my mileage based on my trip odometer & gallons to fill back up full, going @ 70-75 mph the whole trip & it was @27 mpg. In 2003 I drove from Marathon FL to Tampa one a full tank, F to E with low fuel light on at the end, @380 mile but that was going on average 90 - 100 mph.

BTW @27 mpg is with 4 new Goodyear Eagle ResponsEdge tires (215/60/15) with about 1,500 miles on them set at 29 psi cold.

27 mpg is a stretch. Florida must be totally non-stop and flat in all directions. Did you use cruise control? What's the engine rpm at 70-75 mph? Maybe the later models get better gas mileage? 380 miles on a tank full is 20-21 mpg.

I once got 29 mpg in my 240Z (4-spd manual trans) taking Highway 88 home from Lake Tahoe (big time down hill from Carson Pass; over 10K feet) with some coasting time too.

[Gerardjg]

My 95T mostly highway with cruise gets in the low to mid 20s my 97 rarely on the highway with my wife's daily commute at 3 miles round trip gets about 15

[J30inthe sun]

27 mpg is a stretch. Florida must be totally non-stop and flat in all directions. Did you use cruise control? What's the engine rpm at 70-75 mph? Maybe the later models get better gas mileage? 380 miles on a tank full is 20-21 mpg.

I guess I should have said @26 mpg, thinking back about it I remember it was 26 point something. I wonder if there was any drafting effect because I remember following alot of traffic.

I rarely use cruise control & was not using it on that trip. I was really suprised myself, that was the best mileage ever recorded with the car. Obviously high speeds decrease the mileage hence the 20-21 at faster speed, I was really lead footing it that trip. (I did't check to see how many gallons it took to fill back up on that trip for the mileage) If I am not mistaken as soon as the low fuel light comes on it usually takes about 16 gallons to fill back up. Assuming I burned through one of those "low fuel light on" gallons that would be 380 miles divided by 17 gallons = @22 mpg.

The strech of road from Naples to Ft. Lauderdale, AKA "Alligator Alley" is about 110 miles dead flat & straight. It cuts right across the Everglades.

If I recall correctly 3000 rpms is 80-81 mph.

Modified by J30inthe sun at 8:00 PM 3/16/2009
Modified by J30inthe sun at 7:06 PM 3/21/2009

[HymroD]

Florida must be totally non-stop and flat in all directions. .

Yeah!

And let us not forget, full of malcontents, pederasts and the like..

Pe@ce,

HymroD

[J30inthe sun]

full of ...PEDERASTS ...HymroD

I find your post highly offensive.

In defense of all Floridians, I thought PEDERASTS were only found in San Diego driving convertible "INFINITY" M30s.

Only PEDERASTS don't know how to spell Infiniti.

Seriously, if you don't have anything meaningful to contibute please keep your comments to yourself.

In other words... SHUT YOUR PIE HOLE!


Modified by J30inthe sun at 8:54 PM 5/10/2009

[yodawill2000]

Get a Rope........

[Victor]

I have a 94 J30T also and get 16 mpg in local stop and go traffic and 24 mpg for freeway driving with no traffic jams. When driving on the freeway I always use cruise control if traffic conditions allow and usually set it at 72 mph. I drive aggressively during local traffic even though I'm getting to be an old fart.

[kickenkrazy]

97 gets 18-20 driving little heavy footed car come factory with window sticker that says 18-22

[J30inthe sun]

27 mpg is a stretch. Florida must be totally non-stop and flat in all directions. Did you use cruise control? What's the engine rpm at 70-75 mph? Maybe the later models get better gas mileage? 380 miles on a tank full is 20-21 mpg.

70 mph = 2600 rpm80 mph = 3000 rpm

Last trip 258 miles with cruise control set at 70 mph entire trip non-stop, netted 25.9 mpg,:

After trip:

Fill up & top off reading:

After fill up (note same mileage to car):

Same trip in reverse but no cruise control & speed between 80 - 90 mph entire trip @22.5 mpg:

Fill up:


Modified by J30inthe sun at 7:49 PM 5/10/2009

[unlimited]

80-90, someone wasn't obeying the 65-70 speed limit, lol

and man, everytime it's sunny here in Texas and i'm driving with the sunroof open, car glistening, the sentence "j30 in the sun" pops in my head, X]

anyway, 22mpg without cruise control is really good for 80-90mph to me. my car never manages that, but it needs some work under the hood so i'm not suprised. i did a trip not too long ago that was 298mi and it took me 1 1/2 tank doing 80-100 just to make it. was not happy at all.

[puck]

Day to day I drive 2 miles to work. That gets me about 15 to 17 mpg.

I drive about 360 continuous miles every 2-3 months from Cincinnati to St. Louis. I get 24 to 27 mpg depending on how I drive. If I average 80-85 I get about 24 mpg. If I average 65 to 70, I get 27 mpg.

[Jakw]

The highest I've ever gotten was like 26.8. I was driving ssoooo lightly on the pedal, and pretty much the whole trip was windows closed, probably no accessories but the radio, cruise control set at 65, etc.

I used to consistently get around 24 mpg driving from Greeley, CO to Keystone/Breckenridge and back. That's about 2 hours each way, through the mountains, doing from 70-80mph. This was with clean EGR tubes, clean MAF/connections, clean throttle bodies, and probably some other stuff of that nature that I can't remember. And yes, I know how to accurately calculate my mileage.

Nowadays, more of my driving is in the city. I only average 19-21 most of the time.

Oh yeah, and one more thing: Driving 'lightly' to me means the rpms barely ever go over 2000rpms when accellerating. If your 'driving lightly' means 'only' revving to 3000 or 3500, and you still go above that sometimes, that might be why your gas mileage is low. If you really, really want to max out your mpg, start coasting as soon as the light turns yellow, anticipate green lights so you don't have to stop completely before accelleration, drive like there's a full glass of water sitting on your dash, etc. That's the kind of stuff that makes the biggest difference for me.

[Q45tech]

Remember EPA test of that era required that J30 be optimized for 55-60mph.

As to the injector volume of a idle squirt it is very tiny. If the engine ingests 5 grams of air per second then it needs 5/14.7 or 0.340 grams [340 milligrams] of gasoline per second.

650 rpm is 10.8333 rev per second and each rev fires 3 injectors so 340 milligrams divided by 10.833 x 3~~~~ [32.5] so each injector fires 1.046 milligrams of gasoline at idle.

Back to 340 milligrams per second if gasoline weighs 6.2 pounds [2815 grams] per gallon. 8280 seconds or 138 minutes to burn a gallon of gasoline at warmed idle after 10 minutes of warm up at 650 rpm in park.

A little less than 1/2 gallon per hour.If you add any load by having transmission in gear or ac on or power steering turns or lights, heater fan it can increase consumption by 50%.

For comparasion cruising 55 mph is ~~ 2.3 gallons per hour.

Always best to think like pilots do in pounds of fuel per hour of operation.

[J30inthe sun]

...if gasoline weighs 6.2 pounds [2815 grams] per gallon...

Correct me if I am wrong but doesn't the weight per gallon (a measure of volume) of gas change with ambient tempurature? Denser at lower temps results in 1 gallon weighing more at 40F than 90F.

So wouldn't "so each injector fires 1.046 milligrams of gasoline at idle." be dependant on ambient temps?

In other words shouldn't your equations be expressed in volume rather that weight?

[yodawill2000]

From Wiki

The weight won't change a bit. Weight is proportional to mass, which is related to the amount of matter, and matter may be neither created nor destroyed.

However, the denisty of the gas changes. It becomes less dense as it heats up. Put another way, a gallon of warm gasoline will weigh less than a gallon of cold gas. The volumes are the same, but since the densities are different, they don't have the same weight. But if you started with, say, 10 pounds of gas, you would still have ten pounds of gas no matter what its temperature.

BTW, when pilots fuel their planes, they measure the fuel in pounds rather than gallons. A thousand pounds of fuel is a thousand pounds of fuel no matter what its temeprature, so the pilot can determine whether or not he can make his destination without having to throw mama from the plane.

[J30inthe sun]

...The weight won't change a bit...

OK

...Put another way, a gallon of warm gasoline will weigh less than a gallon of cold gas...

OK

...the denisty of the gas changes. It becomes less dense as it heats up... a gallon of warm gasoline will weigh less than a gallon of cold gas. The volumes are the same, but since the densities are different, they don't have the same weight...

My point precisely which is why the equation should be in volume not weight.

Someone filling up there gas tank in the middle of winter in Canada will have more mass that someone filling up there tank in the middle of summer in Las Vegas.

"so each injector fires 1.046 milligrams of gasoline at idle." Truth to this statement would be totally dependant on ambient temps.

[yodawill2000]

The key phrase is "The Volume stays the same"