I have been getting pretty bad mileage and incidentally have also been reading a bunch on both production car and race car aerodynamics....so this has me grasping at straws as to what might be the cause of my mileage...

I am lucky to get 16-17 MPG right now and that is highway/city mixed.

So long story short, I am on a data finding mission.

Could I get you guys to tell me the following:

Current Mileage:_____
Current MPG (miles per gallon):______
Undertray (Y/N):_____ If Y, stock or aftermarket?:__________
Rear Diffuser (Y/N):____
Mudflaps (Y/N):____
Splitter (Y/N):_____
Canards (Y/N):______
Wing (Y/N):______ if Y, stock or aftermarket?:_____________
Full flat bottom on car (Y/N):_____
Fuel:___________
Aftermarket Cams (Y/N):_______
Aftermarket turbo (Y/N):_______
Size tires:_______________
Approx HP on current tune?:_____________

Thanks a bunch

 

Current Mileage:57000
Current MPG (miles per gallon):20
Undertray (Y/N): N
Rear Diffuser (Y/N): N
Mudflaps (Y/N): N
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): Y if Y, stock or aftermarket?: Stock
Full flat bottom on car (Y/N): N
Fuel: 93
Aftermarket Cams (Y/N): 272
Aftermarket turbo (Y/N): N
Size tires: 245/40/17
Approx HP on current tune?: 360

 

Current Mileage:54500
Current MPG (miles per gallon):21
Undertray (Y/N): N
Rear Diffuser (Y/N): N
Mudflaps (Y/N): N
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): Y if Y, stock or aftermarket?: Stock
Full flat bottom on car (Y/N): N
Fuel: 93
Aftermarket Cams (Y/N): N
Aftermarket turbo (Y/N): N
Size tires: 235/45/17
Approx HP on current tune?: 250 no tune yet

 

Current Mileage: 62,000
Current MPG (miles per gallon):17
Undertray (Y/N):N
Rear Diffuser (Y/N):N
Mudflaps (Y/N):N
Splitter (Y/N):N
Canards (Y/N):N
Wing (Y/N):Y if Y, stock or aftermarket?:Stock
Full flat bottom on car (Y/N):N
Fuel:E85
Aftermarket Cams (Y/N):Y
Aftermarket turbo (Y/N):N
Size tires:235
Approx HP on current tune?:382WHP 430tq

 

I feel you on the poor mileage deal. I get 17 if I am very lucky, but i kind of new when I went E85 that I'd go through lots of gas. Its a good thing E85 is so much cheaper.

 

I should add my mods are

Greddy Ti-C 80mm TBE
Walbro 255
Injen intake w/UICP & LICP
AMS 3.5 FMIC
Evo 9 BOV
MBC 20 psi


It might be important to know that as well.

 

You have three options in my opinion to help your mileage

1. Lower the car, if you look at the wind tunnel currents on a lowered car, the pressures of a lower car will of course make you more aerodynamic with less wind drag

2. stay out of spool/ slow down. I do not have an evo to compare your numbers but my gsx is similar to weight. at 74 mph I get 24mpgs, at 67 mph I get all of 27mpg and I never go above 2 inches mercury, at 74 i boost up to 3psi on the highway to keep speed -- highway speeds become a physics problem with wind drag force pushing against your car, every mile per hour slower = less push from the wind. basically on your commute to work, give yourself 10 min more in the morning and your gas mileage and pocket will thank you greatly

3. rebuild your tranny, i hear you guys complaining of turning 4K rpms at 80, so rebuild your tranny and look into a 15% longer 5th gear, companies sell them ive heard


theres a guy whose running duel walbro 255 pumps and has 550 awd hsp with a great tune. hes getting 27mpg on the highway running at 72mph
hes on dsmtuners with his 99gst ( converted to gsx )

a great tune will do you good as well

 

I have 193,000 miles in mine. Never tuned, stock wing, 245/17 tires, missin front undertray, Ralliart lip, pretty much stock except for Injen intake and Trust exhaust. I get anywhere from 23 to 26 mpg on the highway. 21 in the city as long as I take it easy. Another thing is that my dad put some magnets in the fuel line that soppose to align the petrol molecule for better combustion.

 

Woah^^ Close to 200k there. Props!

Current Mileage: 54,xxx
Current MPG (miles per gallon): 20ish
Undertray (Y/N): No
Rear Diffuser (Y/N): No
Mudflaps (Y/N): No
Splitter (Y/N): No
Canards (Y/N): No
Wing (Y/N): Stock
Full flat bottom on car (Y/N): No
Fuel: 93oct
Aftermarket Cams (Y/N): No
Aftermarket turbo (Y/N): No
Size tires: 245-40-18
Approx HP on current tune?: Approx 350whp, Very good 30psi tune.

 

Current Mileage: 62,200
Current MPG (miles per gallon): 17
Undertray (Y/N): N If Y, stock or aftermarket?:__________
Rear Diffuser (Y/N): N
Mudflaps (Y/N): N
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): Y if Y, stock or aftermarket?: stock w/ oem VG
Full flat bottom on car (Y/N):_____
Fuel: California 91 craptane
Aftermarket Cams (Y/N): N
Aftermarket turbo (Y/N): N
Size tires: 255/35/18_
Approx HP on current tune?: 273 awhp @ 21 psi

I have noticed recently my fuel economy is slightly worse than usual. I think my plugs are just not as fresh. Using 90w vs 140w in the rear diff was good for another 20 miles per tank, and close to it in the TC cause now im also using 140w in the tc, 90w for trans, and 140w in rear diff so that caused economy to go down.

 

Current Mileage: 37,XXX
Current MPG (miles per gallon): 18city/28highway
Undertray (Y/N): Stock
Rear Diffuser (Y/N): N
Mudflaps (Y/N): N
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): Stock
Full flat bottom on car (Y/N): N
Fuel: 93 or 92
Aftermarket Cams (Y/N): FP4r
Aftermarket turbo (Y/N): N
Size tires: 235/45/17 - Winter tires
Approx HP on current tune?: 355

Also, currently stock ride height, TBE, IC pipes, etc. for the tune of 355.

I typically cruise at 75-80mph (dependng on the state) and can easily stay out of boost - but it would be MUCH easier with CC!! I can cruise at speeds up to 110mph without needing boost...

 

Current Mileage: 23k
Current MPG (miles per gallon): 19 to 20mpg - about 90% city driving
Undertray (Y/N): Y If Y, stock or aftermarket?: stock
Rear Diffuser (Y/N): Y
Mudflaps (Y/N): Y
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): Y if Y, stock or aftermarket?: stock
Full flat bottom on car (Y/N): N
Fuel: 91
Aftermarket Cams (Y/N): GSC S1
Aftermarket turbo (Y/N): N
Size tires: 255/35/18
Approx HP on current tune?: 315

I'm also lowered on Swift Sport springs and I'm rarely on boost.

 

Answers below

 

Current Mileage: 66,000
Current MPG (miles per gallon): 22-27
Undertray (Y/N): Y If Y, stock or aftermarket?: Y
Rear Diffuser (Y/N): N
Mudflaps (Y/N): N
Splitter (Y/N): N
Canards (Y/N): N
Wing (Y/N): N
Full flat bottom on car (Y/N): N
Fuel: 93
Aftermarket Cams (Y/N): N
Aftermarket turbo (Y/N): N
Size tires: 245/40/17
Approx HP on current tune?: 251

Mods are in my sig. If I half throttle and slowly spool while getting on the highway I get 22-24 on my daily commute. If I shift below 2500 and slowly get up to crusing speed, 65-75, I get 27. My daily commute is 70% highway speeds and 30% city driving.

 

Current Mileage:60060
Current MPG (miles per gallon):22-25(needed new clutch so i couldn't boost at all but still getting good mileage now that i boost only a little after broken in
Undertray (Y/N):yes If Y, stock or aftermarket?:stock
Rear Diffuser (Y/N):no
Mudflaps (Y/N):no
Splitter (Y/N):no
Canards (Y/N):no
Wing (Y/N):yes if Y, stock or aftermarket?:stock
Full flat bottom on car (Y/N):no
Fuel:chevron 91, california's highest grade available
Aftermarket Cams (Y/N):no
Aftermarket turbo (Y/N):no
Size tires:235/45/17
Approx HP on current tune?:258 stock, 285 tuned on tbe, licp, intake, boost pill