SC400 Gas Mileage Issue
#1
Rookie
Thread Starter
SC400 Gas Mileage Issue
Hey guys, i got a problem with my sc400. I have a 1998 Sc400 114k on the dash , it is giving me some issues. I'm getting 16 mpg and that's me driving calmly. I have a couple friends who are getting 18 mpg same year without an issue and they beat on their cars more than i do. I brought my car to 10 different mechanics and none of them had the answer to the problem. I change my battery, alternator, air filter , fuel filter , spark plugs, and used techron this was all done about 5,000 miles ago. I do my oil changes every 3k miles Mobil 1 fully synthetic 5w-30 and i fill up my car with BP, Exxon, Hess and Sunoco gas super all the time. Its weird i cant get to the bottom of this and find out why. Any comments, ideas , or help would be greatly appreciated .
Thanks for reading
Thanks for reading
#2
Lead Lap
iTrader: (2)
The only two other things I can suggest is check your brake caliper pins to make sure they're not frozen and check the wheel alignment. But to be honest, 16-18mpg in the city is pretty normal. I'd only worry about it if you were getting this kinda mpg with a lot of freeway driving.
#6
Lead Lap
iTrader: (2)
Nope, unless both the upper and lower pins are frozen, it won't be "extremely" obvious with just one of the pins being stuck. Brakes might heat up a bit more than usual, but won't be burning hot since the brakes always have a small amount of drag by design, even when the pins are greased up and working properly. I had a frozen pin on one side and didn't notice till it came time to change my pads out.
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#8
Instructor
iTrader: (1)
PCV valve, and raise your tires to 32 psi.
If that doesn't change anything, then replace the O2s (only the 2 primary's). They're due to be replaced anyway because of the age, but because they can be a real nightmare to change, I always tell people to replace them last
Also, inspect all your factory ground wires. Follow the - wire from the battery to the chassis and the engine and see its condition.
#9
Lexus Test Driver
If your using a MPG dash counter, Reset it and start over. It could be just an estimated average of you and a bunch of other factors. ALSO switch up gas stations and run with one specific brand of fuel. I used to get from a local Citgo and half tank 93 premium driving around town would last 2 days (no more than 40 miles) but I switched up to Shell and I drove to CT 60 miles each way (120 total) and still have a quarter tank from a half
#11
Driver School Candidate
You may want to change the capacitors in your ECU
I had this same exact issue...I was getting 10-12 MPG on my SC400 1992.
I bought it @ 111k and it was super clean but it had terrible gas mileage so I started searching CL.
Here's what I found:
https://www.clublexus.com/forums/ls4...capacitor.html
If you haven't already, change out the caps since they probably need to be replaced.
Good Luck!
p.s. I saw that you're in NJ...if you send me the ECU I can help you with this.
I bought it @ 111k and it was super clean but it had terrible gas mileage so I started searching CL.
Here's what I found:
https://www.clublexus.com/forums/ls4...capacitor.html
If you haven't already, change out the caps since they probably need to be replaced.
Good Luck!
p.s. I saw that you're in NJ...if you send me the ECU I can help you with this.
#12
Rookie
Thread Starter
I had this same exact issue...I was getting 10-12 MPG on my SC400 1992.
I bought it @ 111k and it was super clean but it had terrible gas mileage so I started searching CL.
Here's what I found:
https://www.clublexus.com/forums/ls4...capacitor.html
If you haven't already, change out the caps since they probably need to be replaced.
Good Luck!
p.s. I saw that you're in NJ...if you send me the ECU I can help you with this.
I bought it @ 111k and it was super clean but it had terrible gas mileage so I started searching CL.
Here's what I found:
https://www.clublexus.com/forums/ls4...capacitor.html
If you haven't already, change out the caps since they probably need to be replaced.
Good Luck!
p.s. I saw that you're in NJ...if you send me the ECU I can help you with this.
#13
Driver School Candidate
I live in bergen county but my buddy has his equipment in Carteret right off the turnpike. So if it doesn't work just shoot me a message.
We were able to replace everything in about 2 hours.
good luck!
We were able to replace everything in about 2 hours.
good luck!
#15
Rookie
Thread Starter