99GS400HP

In my 99 GS400 with 140k miles im getting:
13mpg Mixed city and highway driving.

tmf2004

iTrader: (15)

that's pretty low IMO

sam12345

iTrader: (1)

Gas mileage has a lot to do with how fast you accelerate. If I floor it at every opportunity up to the speed limit. Of every time I take off from a stop sign I am at 3/4 throttle or more then I will get 13 in all city driving. I have not gone to a race track yet but I suspect then it would be 5 mpg. So how do you drive 99ge400hp plus do you have a turbo or supercharger? Sice how else are you getting 400hp?

aneidiaz

Mine wastes gas of course lol it's a V8 guys. But if you drive slowly or in cruising my mode so to speak the gas tends to last. What I try to do is never go over 2300 rpms and that usually works for me. I can hit 80 on the highway under 2500 rpm comfortably.

islexusred

Hit 80 mph under 2300 rpms? How? Any mods? My 98 gs400 reaches close to 3000 rpms at 80 mph...

DMPesso

Your mileage sounds about right, im in NYC like KINGNASGS4 and we both get the worst mileage, the most stop and go the worse the mileage is, thats why people living in their red neck places like texas and utah get super mileage because they hardly ever stop and go (no offense red necks ;-). 10 MPG seems low unless you do alot of idling with the car on mine gets low mileage when im idling alot and doing all city driving. Othen then that it can ONLY be spark plugs, O2 sensors, MAF sensor(highly doubt), bad cheap gas, air filter, tire pressure, horrible alignment (will destroy MPG), and also the tires. Other then that there is not much you can do besides get rid of the V8, but then you will be missing it...

gsean400

I was going to say... Cheap gas makes a big difference, Valero, Arco gas will for sure decrease your mileage. I noticed a 2mpg increase just by switching to shell.

tmf2004

iTrader: (15)

I always use a fuel injected cleaner every so many miles. especially with my car sitting more than I drive it i tend to use chevron addictive or a seafoam.

I always use shell mostly or lately it's been BP. BP offers no ethanol but never tried it

1QWKGS4

iTrader: (3)

Yup, I'm the same. I use Chevron techron or Seafoam in the gas tank and I use Liberty non-ethanol gas since its the only one available in my area with no ethanol.. (stay away from ethanol if you can)

If I take a trip, of course, i'll have to use ethanol gas but when I get home I re-fill with non-ethanol gas.

Tony, you don't want to let your car sit for long periods with non-ethanol gas.. (I read it corrodes your fuel system)

tmf2004

iTrader: (15)

thanks Don....

Don, do you notice a difference between ethanol and non ethanol ?

1QWKGS4

iTrader: (3)

Difference in power, I can't really tell but my 400 idles better (low idle issue) with non-ethanol gas and of course i get about 2 mpg better..

KingNasGS4

iTrader: (22)

What stations sell non ethanol gas? Over here I don't think that I ever saw it. Usually on the pump it says that it contains ethanol.

1QWKGS4

iTrader: (3)

Ethanol is pretty much everywhere these days, you have to search online on Gas Buddy or some other sites that list non-ethanol stations in your area, its very dependent on where you live, some cities or states don't have non-ethanol at all.. Its ridiculous it has come to this - having to search for pure gas, I feel like Mad-Max.. lol

1QWKGS4

iTrader: (3)

this is the site to find non-ethanol stations.. http://pure-gas.org/

tmf2004

iTrader: (15)

thanks don, I may have to give it a try with a tank of pure ethanol. will it harm the engine in anyway from switching from non ethanol to ethanol