what can cause the gas mileage to go down?

[llacap]

My NSX usually gets around 280miles per fill up. I've heard people on here go as far as 400+ miles per fill up. In an attempt to find the source of my fuel economy issue, I would like to find out what are the factors which I can investigate.

I have a 92 with 18/10 combo 215/35/18 and 275/20/19. Only modification is JGTC center exit exhaust and dinan chip.

 

[shawn110975]

Alot of those chips all they do is trick the ECU into thinking your car isnt getting enough air/fuel mixture, puts it into a programming mode I forget what its called, to get that " extra HP " they claim,
I would think thats the problem, but could be anything. have you tried fuel injector cleaners, gas treatments,
I have had great experience with a product called SEA-FOAM, you pour it directly into your engine oil, pour it into you gas tank, its cleans everything, its great will not hurt your engine.

my 2 cents.

 

[zxtec]

Heavy foot? :wink:

 

[BTL3.0]

clean injectors, clean air filter, clean fuel filter..drive like Grandma, use cruise control on highway...shift at oh i dunno, lets say 2.5k-3k every gear..i think all that would help in getting better gas milage. but then again, you do drive an nsx..it's hard to not have a little fun with it..

seafoam is great..i've used it in my other car to clean out the system..

 

[tosugrad]

tire pressure?

 

[mskrotzki]

Gas

Some states also use different mixtures for pollution purposes. Colorado has different gas in the summer and winter to try to cut down on Ozone in the winter. I can always tell the difference as soon as it changes.

I've had my car in 40 states and noted huge differences in mileage depending on where I buy gas. Sorry to say California is just about the worst. Mid west and South are pretty good.

 

[MaxGeek]

A person who gets 400 miles per tank is probably 90% freeway.

 

[FogCityNSX]

Gas

Some states also use different mixtures for pollution purposes. Colorado has different gas in the summer and winter to try to cut down on Ozone in the winter. I can always tell the difference as soon as it changes.

I've had my car in 40 states and noted huge differences in mileage depending on where I buy gas. Sorry to say California is just about the worst. Mid west and South are pretty good.

+1

I got 28-29 mpg in Texas doing a minimum 85-90 mph highway no cruise control. In Colorado, it was about 26 mpg. In california, I get a MAX of 24 mpg doing 65 mph with the cruise.

Tune up? Plugged up air filter or Cat? Bad coil or plugs? Heavy foot?

Are you talking 280 city mileage? That's not bad. I get minimum 20 city with a semi heavy foot.

What did you get before?

 

[Cozmo]

Heavy-ass 18/19" wheels I'm sure have a LOT to do with it.

 

[FogCityNSX]

Heavy-ass 18/19" wheels I'm sure have a LOT to do with it.

Not so much. I've ran at least 5 different wheel set ups from oem to boat anchor lowenharts in 18/19. That alone was about 7+ lb difference in EACH rear rim alone, not including tire weight. Never had a change in economy that I could detect city or highway. I consistently track my mileage.

If we were talking like oem to 35+ (trucks), then the change would significant.

 

[Malibu Rapper]

A person who gets 400 miles per tank is probably 90% freeway.

I agree. I don't think I've ever gotten 400 miles out of a tank. 280 miles out of a full tank isn't a fuel economy issue IMO. Depends on how you drive more than anything... If all of a sudden you went from 400 miles to 200 miles, then I would be more concerned.

 

[Big_D]

There are so many variables such as your driving habits and whether its city driving or on the hwy. How fast do you drive? Use cruise control much? Are you granny shifting at 2500 rpm? Are you running the A/C? Are your tires at 33psi F 40psi R? Do you have a new air filter and good plugs? Maybe you need do a Throttle Body service...those are the biggies.

 

[NSXrunner]

Environment? If you live some place flat...good to go. Throw in some hills, buh bye gas. My best example for this is my Honda Fit. Throw me someplace relatively flat and open and i can get up to 40mpg, put in some climbs and it will drop to around 31mpg.

 

[FogCityNSX]

Could also be the chip fattening up certain parts of the rpm band

 

[Acura NsX Pilot]

In an attempt to find the source of my fuel economy issue,

I belive this is the major reason for bad fuel economy in the Nsx

 

[nsxtasy]

My bet is that the biggest difference is that you aren't putting as many gallons in your car when you fill it as other people do.

Suppose you do a mix of city and highway driving, and you fill your car with 12 gallons when the gas gauge reads a little over 1/4 tank. That means your 280 miles give you 23 miles to the gallon.

Suppose someone else gets 23 miles per gallon in a mix of city and highway driving, and they drive 40 miles past when the low fuel warning light goes on, then fill it with 17.5 gallons. That means his 400 miles gives him... 23 miles to the gallon. :smile:

This is why it's meaningless to discuss mileage in terms of miles per tank. What matters is miles per gallon.

 

[FogCityNSX]

This is why it's meaningless to discuss mileage in terms of miles per tank. What matters is miles per gallon.

Wow, good eye. Usually I catch those but this time I automatically defaulted to mpg.

BTW, nice having you back Ken. I left for a long time and came back recently. However.... it didn't take long to remind me why I left in the first place.

 

[llacap]

thanks for the insight. it's probably time to change the air filter, check the tire pressure and definitely keep a better eye on how much i put in at the tank.

 

[jdryley]

If you have recently had an oil change a decrease in fuel economy could indicate that too much oil was installed.

 

[Acura NsX Pilot]

If you have recently had an oil change a decrease in fuel economy could indicate that too much oil was installed.

Reallly .... im serious but is this really true or a myth ?

 

[nsxtasy]

I've never heard anyone say that before.

 

[NSXrunner]

If you have recently had an oil change a decrease in fuel economy could indicate that too much oil was installed.

I have actually heard this way back when, from one of the Integra guys. Never got any confirmation on it though.

 

[FelonyRuckus]

i've never installed oil....

 

[DocL]

I've found that I get significantly worse gas mileage when I haven't driven the car in 4-6 weeks. I guess keeping it mostly in 2nd gear to hear the exhaust may have something to do with it. :biggrin:

 

[FelonyRuckus]

I've found that I get significantly worse gas mileage when I haven't driven the car in 4-6 weeks. I guess keeping it mostly in 2nd gear to hear the exhaust may have something to do with it. :biggrin:

+1




i would guess checking tire pressure too