I recently picked up an 02 SL1. Only got about 400 klms highway on a full tank of gas. I did some research here and replaced, plugs, wires, ECTS, thermostat, new coolant, air filter and fuel filter. Now i get only 450 klms hwy to a full tank. I bought this car for fuel efficiency but 450 klms hwy is not efficient. The heat gauge was just past 1/4 before and after work. Car has more power since tune up but why such terrible fuel consumption. What else can i check i am stumped. I would be very grateful for any and all help.

Thanks
Don

 

Not trying to be insulting but do you drive in a hilly area? I just moved out to Pittsburgh from New Jersey and it is crazy hilly out here so my gas mileage now sucks.

Also can you pls translate the mileage into MPG for us? It'll assist us in evaluating your situation a little faster

 

Maybe you need to clean the throttle body and change the thermostat. How far are you driving the car? If it's short trips, it never gets up to proper operating temp and your mileage will suck with a cold engine.

 

All good points... Fuel mileage can also depend on driving habits, and the transmission type... Is it manual or auto? Do you drive fast or accelerate really quickly? My Suzuki with a five speed was getting 27 ish mpg, I changed my driving habits, slowed down a little, and was getting low 30s on a tank...

 

The conversion would be 280 miles to a tank.
I drive 170 klms or aboug 130 miles to work and the same back
Already changed thermosatat.
Fairly level ground driving.
How would i get to throttle body on these cars?

 

The temp gauge is about right, two needle widths above the 1/4 mark. If the coolant doesn't reach 80C in a calculated time frame based on outside temp and driving conditions, the check engine light will come on. It is very sensitive to this. Mine came on at 79C just seconds after the calculated time, twice so when that happened, I changed my thermostat.

Is this an automatic transmission or a manual? A manual transmission should get you about 38-40 mpg highway. Driving style can affect this, I get upwards of 42 mpg while my son only gets about 34 under the same conditions. He varies his speed more than I do.

What is your idle speed? If you are idling at 950 or higher in neutral or with clutch in and engine warmed up, then look for a vacuum leak in the intake manifold gasket around the #1 cylinder. Spray a little oil or starter fluid or carb cleaner around it, particularly in the upper outside corner and if the idle is affected in any way, you have a leak.

This is a common problem on this engine. If you have one, do not replace it with a factory gasket, use a felpro instead. The felpro is stiffer and won't get sucked in like the factory gasket does.

Edit: 38 mpg translates to about 16 km/l or 6.2l/100km, or 73.5 km/imp or 45.6 miles/imp. Are you sure the BCM is set to km and not miles? How many liters, imp or gallons to fill?