opelmanz

My 2003 Lexus gets about 18 mpg average and I am about 75% freeway 25% city. On the freeway, I get about 24-26mpg depending on speed, usually better closer to 80mph, lower closer to 55mph.

I previously got worse mileage. My car has 200K on engine and about 50K on rebuilt tranny. New plugs last year. Cleaned MAF once in the last year. ALWAYS put Chevron 91 in her and keep tank half full. Air in tires checked regularly. I used to have some engine codes, but a new oxygen sensor and code clearing fixed it. I also just recently did drain/flush on tranny.

Above posts provide EXCELLENT tips on getting better gas mileage, even the tip about looking at instant MPG using the info screen. You will notice that the RX gets terrible mileage when accelerating, even modestly, but as soon as you are cruising at speed it jumps up (no surprise). Easiest way to increase mileage is to accelerate slowly and drive slower. I used to drive a little faster, but after getting this car and seeing the cost of filling a tank rise, I slowly started becoming a much slower and more careful driver.

Best of luck in your mileage efforts

MarcusF

Small update on my reset MPG, it's been going up, and now sits at about 17.1 - 17.5

PSURobert

My drop off in highway mileage from 22-23 mpg to 18-19 mpg at 148,000 miles coincided with a sudden excessive oil consumption problem on a 1,000 mile trip last winter. Turns out my pcv valve was clogged and clicking, which I think led to blow by and perhaps a stuck piston ring. I'm working on that problem with the MOPAR combustion cleaner treatment listed in the forum's excessive oil consumption thread. My point here is to remind folks to change or at least check the pcv valve at reasonable intervals, like every 60,000 miles, despite the fact that neither the factory owner's manual nor the scheduled maintenance supplement mention the pcv at all.

jcruise

Hello, I am new to this site and have owned a 1999 Lexus RX 300 for 5 years. The vehicle has 136,000 miles on it. About three years ago I noticed two things with this vehicle my mileage dropped off to about an average of 12 mpg. With the type of neighborhood driving I do I typically get 15.5 to 16.5 on average from winter to summer weather. I also had an oil stain under my vehicle. I learned that Toyota uses crank case pressure with the ECU to make air fuel adjustments. So if you do not have the correct crank case pressure you will loose MPG. I had to change my valve cover gaskets. It is quite a job. I am retired and it took me two days. My mileage is back to where it was and no oil leaks. Highway mileage is good at 24 mpg.

Baetke

Please share where you learned this from. I'm pretty familiar with all the systems on this engine and I have never heard or read anything of the sort. That being said, if there is truth to it there are a lot of us that would love to figure out how to get 25mpg again.

AnthonyMtz

I use nothing but premium gasoline in the Rx but can't get more than 220 miles on a tank! I literally average 12 mpg in the city and 16 mpg on the highway and usually 14 mpg mixed...oil changes are on time, new spark plugs, tires up to pressure and have no extra weight In it. its got 176k on the clock it's driving me nuts! Thanks in advance

salimshah

Have you looked at the sticky terrible milage thread?

Salim

lexus114

did you try cleaning the maf sensor in the air filter box?

lexus114

something is not right. maybe time for new fuel air ratio/o2 sensors

AnthonyMtz

I don't know guy's...I guess I'll start pricing them out cause I get like 220 per tank and it's driving me nuts!

AnthonyMtz

Idk if this is the problem but when my "spark plugs" got changed apparently they have bosch spark plugs instead of the denso ones that were supposed to be put in, I took one of the bosch's out to inspect it and it's all white on the bottom....never having that mechanic do work on my baby anymore!

carguy07

"Botch" plugs are bad news on these cars (and every other car I have tried the on too). Replacing them with NGK or Denso would be a real good place to start.

wotcham8

My 03 RX300 FWD averages 14.6 mpg driving around Maui. No freeways on Maui.

jcruise

Need to ask a few questions;
- are you viewing your gas mileage on averaging or instantaneous?
- averaging mpg gives you a better idea of overall performance.
- understanding the instantaneous reading is mpg at any time the accelerator is pressed or released. When you coast to a stop your mpg will increase as much as 100 mpg. When you at a full stop at a light you will see 0 mpg. So what have you selected on your dash?

- are you leaking engine oil on the ground? Toyota motors use crankcase pressure to calculate mpg. If you have engine oil leaks they need to be fixed to increase mpg. I had valve cover leaks and it cost me ~2.5 mpg. After the repairs I now get 15.5 mpg city driving, highway at 23 mpg (english units).

- new spark plugs always are a good thing at 100,000 mile intervals

- also this is a biggie. if you have about 100,000 miles on the Harrier has the timing belt been changed. This is critical and will definitely affect engine performance. So, this is the most serious issue on engines. Does the engine run smoothly? if not, if it's rough at idle, there may be damaged valves from a worn timing belt that jumped a tooth. These belts are rubber and can cause engine valve damage if they are not changed at the correct intervals.

I guess that just about covers it.

Best of Luck and take care.

matts6887

I am kinda wondering a few things about improving mileage on these rx's as well. I have a 99 300 awd and i only wish i got 24 mpg on the highway. If Im lucky; sometimes in city stop and go driving with traffic lights etc i will get up to 20mpg; but then at times I will only get like 16mpg which imo sucks. I know they didnt have the engineering and design back then to get as good mileage as they do now; but i did just buy a bottle of complete fuel system cleaner and am waiting til my tank gets close to empty to put it in then fill it back up again and Im hoping that will improve things for awhile anyway. As I have no idea whe the last time a fuel system cleaning was done on this vehicle; so hopefully this fuel system cleaner will help.