I've recently done the caps, rotors, NGK plugs, fuel and air filter, changed oil, diff fluid, trans fluid, new OEM gas cap, and reset ECU in hopes of increasing fuel mileage on my SC4 w/ 154k miles on it. The car runs great, idles perfect, just doesnt get the best mileage- avg. is about 17-19 mixed driving VERY conservatively.

Any suggestions for better mileage? I've contemplated seafoaming it but am too lazy to change the plugs again b/c I read it fouls them after seafoam treatment.
Would changing the ignition coil help?

Any helpful replies appreciated

 

Changing the coils won't increase mileage. What Octane fuel are you using? If it's Regular Unleaded (89) then that's your culprit right there.

 

3400lbs + v8 = gas drinker.

I cant remember what the sc400's estimated fuel consumption is for city and highway but I cant imagine it being that great. On the other hand I dont imagine it was meant to to 17-19mpg, is that in the city or highway?

its a shot in the dark but when last was the timing belt changed? an old belt, that has stretched some will affect the timing on the car. if your belt is very very old, this could be a source as well, but if its been changed fairly recently, then I'd rule out this paragraph.

 

I have been using 89 - midgrade in so cali. My mpg 17-19 is mixed highway and city. I don't know when the timing belt was done as I've only had the car for 8 mths, but when i changed the cap & rotor the belt looked fine.

I'll try 91 and see what happens w/ that. Im thinking I should get better overall mileage since I've read on here other SC4s doing 25+mpg w/ a lot of highway driving

 

or the gas cap for that matter. LOL.

 

I run 93 octane, and average about 19-maybe sometimes 20mpg....

 

increase your tire pressure to a safe level

 

Ive heard of the 98s and up getting better mileage with the 5 speed auto., proper tire pressure, clean air filter, new fuel fiter, and make sure cat. conv. are not clogged. My 95 avrg. 17- 21.

 

i get 25 on the hwy, and pretty low in the city (im a bit lead footed)

 

my car just hit 160k..i used zmax and it helped alot. i also did a tranny flush oil change...wut does new spark plugs do for the car?i havent changed the water pump or timing belt. think its still the original.anyone know when theyre gonna go out on me?should i wait or change it asap. sorry for jacking the thread

 

over 60k ago. good thing it's an import. i'd change that timing belt, and water pump, as you don't want the timing belt to break on this car.