Increasing Fuel Efficiency

[143toyota]

I have a 92 toyota Camry, with 400 KM, on a full tank gas (62-63 L) I cant seem to drive more then 575 highway KM on it, the car is on its second engine, a 2.0 L from japan with approx 50K on it, but when it had the 2.2 L before it wasnt performing any better. at 100Km/h the RPM is about 2800. The car is a DX model I believe, I have another camry that is a 92 but is LE with 315 KM, and that car can drive 800 KM on a full tank, and when at 100KM/h the rpm shows 2100. I just want to know what i can do improve fuel efficiency? I just assumed theres something wrong with the transmission because of the increased RPM. Ive tried most of those fluids sold in stores to improve fuel economy, and it doesnt work, spark plugs, air filter are changed on a regular basis. What can be the problem?

[geoff5093]

For the English members here, thats roughly 357 miles. It's not extraordinarily low, as most members get anywhere from 350-400 miles on a tank of gas, which equals to ~20-23MPG. Theres no way you could get 800KM on a single tank of gas, that would equal to roughly 45MPG!!

EDIT: I just read your last sentence. I would clean the throttle body and intake, and SeaFoam the engine. But as i've said before, the mileage your getting now isn't really that bad.

EDIT2: I guess I just got my conversions mixed up, I was comparing the 800KM to the 357Miles. 800KM = 497Miles, which is much more attainable. Which also equates to 27-28MPG.

[dc_98_cam]

Could be dirty or clogged EGR valve. Check this first. Remove and inspect for carbon deposits.... Could possibly be defective EGR diaphragm .... just have to replace if this is the case. You might be able to test EGR function with a manual vacuum pump ... see if it is actually working.

Other possibilities:
Inefficient combustion for one reason or another ...possible causes/fixes:
Injectors .... not supplying uniform fuel spray pattern .... maybe replace or clean
....Somebody suggested getting oil sample tested for excess hydrocarbon level.
Oxygen sensor ... signaling ECU that too much fuel is require for correct combustion
Check cylinder compression ....
Clogged catalytic converter.

[DFBonnett]

Consider also the possibility that the timing might be slightly retarded. Verify that it at spec.

[xtremeskier97]

Consider also.........searching first.

[dc_98_cam]

convert km to mi .... something like 32 mpg
I can easily get 33 mpg, hwy driving, no major stops.
.... averaging 60-65 mph.

[143toyota]

It could possibly use some cleaning, but 3 weeks ago, I did an emissions test and this car past it easily, and I know I cleaned the throttle valve about a month ago, I will take a look into the oxygen sensor, and check out the timing of spark as well

[gladis]

It also depends on your driving style

I did a granny driving style for about 2/3 of a tank (50/50 freeway/city time wise) and I get 28 mpg

My normal driving (freeway 75% timewise) gets about 25 mph

This tank I'm using I'm not looking at more than 22-23, which is my preferred style of driving (harder acceleration), and this had much more city time than usual

My worst tank in the 40-50 tanks that I've kept track off was 19 mpg, my best was 28 mpg, and average is 22-25 mpg