How Can I Squeeze Some More Mpg Out Of My Rx300?

[k5chevyblazer]

I have a 2000 RX300 that we just bought I am NOT happy with the fuel mileage it is getting. I was wondering what mods I could do to it to help it out. Some type of filter charger kit with an open element? Exhaust that doesnt make it any louder? We havent been doing much freeway with it but in town it is only getting about 15-16 mpg. :cries:

thanks for any help.

[SKperformance]

an intake

motorvac

slightly above tire pressures

premium gas

[TunedRX300]

I have a 2000 RX300 that we just bought I am NOT happy with the fuel mileage it is getting. I was wondering what mods I could do to it to help it out. Some type of filter charger kit with an open element? Exhaust that doesnt make it any louder? We havent been doing much freeway with it but in town it is only getting about 15-16 mpg.  :cries:

thanks for any help. 

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My RX gets 24mpg on freeway, 20 mpg mixed with K&N filter, 87 octane gas, and spare tire and roof rack removed. Tried with 89 octane but got lower mpg, octane 87 is recommened by Lexus and I doubt 1MZFE is tuned for 91/93 octane gas.

[mh6]

Hi Tuned,

any concern with more dirt getting into the engine than normal or does it do a good job of filtering ??

What type of maint. do you do to the filter in your experience thus far ??

Man I would like that same milage if I can. Best I have gotten was on a highway trip to Indiana, doing about 72-73, was 22.1 MPG. That was with stock filter.

Once you hit 75 and RPM's are at the 3000 mark.... milage starts going down.

2800-2850 RPM's seems to be the best economy.

I agree with the octane level .....done test with higher and as you saw I got lower as well...people never beleive me when I tell them that...............glad to see some else saw it as well.

I have a 99 AWD.

[TunedRX300]

Hi Tuned,

any concern with more dirt getting into the engine than normal or does it do a good job of filtering ??

What type of maint. do you do to the filter in your experience thus far ??

Man I would like that same milage if I can. Best I have gotten was on a highway trip to Indiana, doing about 72-73, was 22.1 MPG. That was with stock filter.

Once you hit 75 and RPM's are at the 3000 mark.... milage starts going down.

2800-2850 RPM's seems to be the best economy.

I agree with the octane level .....done test with higher and as you saw I got lower as well...people never beleive me when I tell them that...............glad to see some else saw it as well.

I have a 99 AWD.

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mh6,

Good to see you have a similiar result on higher octane gas. Yes higher flow filters let in more dirt than paper to exchange for better flow. It makes sense if you think about it. This is a tradeoff decision I made - during winter, I use K&N since dusts are minimal during wet season; during summer, I switch back to OEM paper. Here is a good site that has some interesting results. With stock intake the test showed that K&N does not get so much air flow than paper (NAPA Gold) but also filter better than we were led to believe. You can make your own conclusion and decide what is good for your RX.

Air Filtration Comparasion

I also have a custom made cold intake airhorn instead of Lexus OEM intake, which magnified the K&N's higher flow property since more air is stuffed into the engine.

The parts are only $10-15, I found city mpg is about 1 mpg less but highway mpg increased about 1 mpg, but I do get higher horsepower. I have the DIY link if you are interested.

[Lexusfreak]

I have a 2000 RX300 that we just bought I am NOT happy with the fuel mileage it is getting. I was wondering what mods I could do to it to help it out. Some type of filter charger kit with an open element? Exhaust that doesnt make it any louder? We havent been doing much freeway with it but in town it is only getting about 15-16 mpg.  :cries:

thanks for any help. 

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Perhaps a major tune up will help, make sure your tire pressure is correct, take out any additional weight in the vehicle (stuff in the cargo area that might add extra weight etc) & use premium fuel. B)

[TunedRX300]

Don't want to spark a debate on octane, but octane 87 gas is recommendation by Lexus for 00 RX. "Premium" fuel is higher octane but does not mean 1MZFE is designed to take advantage of the higher octane so it could be inferior gas for RX.

Here is a good link Octane FAQ

[VGR]

We havent been doing much freeway with it but in town it is only getting about 15-16 mpg.  :cries:

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15-16 MPG could be about normal for city driving in a city like Sacramento with thousands of streetlights. Out on the highway mileage should be in the low 20 MPG's. If not, returning the engine to near new mechanical condition is the answer to restoring gas mileage. This could involve:

1. New set of factory original spark plugs

2. New set of factory original spark plug wires (if car has more than 60,000 miles)

3. New factory original air filter

4. New oxygen sensor (if car has more than 80,000 miles)

5. Manually cleaning the throttle body http://www.lexls.com/tutorials/EFI/throttlebody.html

6. Install a set of low rolling resistance tires like Michelin MXV4-Plus or Goodyear Viva 2.

The cost of all the above could top $500. However, many owners balk at the thought of spending $500 just to return a car to boring factory original condition and may find themselves drawn to cool and exciting sounding advertizements and websites that promise cheap bolt on power.

[RX in NC]

The conventional RX series is not designed to be particularly fuel-efficient. Overweight, underpowered SUVs are simply not going to approach the all-around 25 mpg that we'd love to achieve. The best and most cost-efficient suggestions have already been posted for you above:

1. Keep your tire pressures up.

2. Drive conservatively, especially when starting and stopping.

3. Keep your filters clean.

4. Keep your spark plugs clean - good luck reaching the three rear ones.

5. Get any unnecessary weight out of the seats, floor, and cargo areas.

6. 87 octane fuel is recommended and just fine for this vehicle.

My wife drives her 2000 RX300 as conservatively as anyone out there. She does a great deal of highway driving and some daily stop-and-go driving as well. I keep the vehicle meticulously maintained and the tires at 36 psi year-round. She averages between 18.5 and 20 mpg, and that's simply the best we're gonna do....

[scoobie]

...

5. Get any unnecessary weight out of the seats, floor, and cargo areas.

...

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Finally, a legitimate reason to throw the mother-in-law out on the street

[speedyg]

I have a 2000 RX300 that we just bought I am NOT happy with the fuel mileage it is getting. I was wondering what mods I could do to it to help it out. Some type of filter charger kit with an open element? Exhaust that doesnt make it any louder? We havent been doing much freeway with it but in town it is only getting about 15-16 mpg. :cries:

thanks for any help. 

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My RX gets 24mpg on freeway, 20 mpg mixed with K&N filter, 87 octane gas, and spare tire and roof rack removed. Tried with 89 octane but got lower mpg, octane 87 is recommened by Lexus and I doubt 1MZFE is tuned for 91/93 octane gas.

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Any idea or guess how many mpg just removing the spare tire would save? What do people think about that idea (is it worth it?) I hear that some cars nowdays don't even come with a spare tire (they come with an inflator can.) If the mpg saved by removing the spare tire is actually noticeable then I would consider doing it...

[TunedRX300]

You are correct that more cars are w/o spare tire and rim. For example, BMW M3 only supply a can and pump to save weight.

Weight itself may not be a big factor in improving mpg, but if you are sensitive to performance shaving off close to 50lb of spare tire + rim does matter. There are people who pay premium $ to have carbon fiber hood to replace a better looking but heavier OEM one.

Another argument is that a 2000 RX300 AWD is 626 lbs heavier than a 2000 ES 300 and less aero dynamic. They are powered by the same 1MZFE engine. If you believe ES is properly powered, then RX is relatively underpowered - any way to improve aero-dynamic (removing roof racks or mud flaps) and reduce unneccessary weight will make RX closer to ES. Remember we are trying to squeeze more out of RX w/o affecting essential functionalities.

[khewlkat]

i also gets 15 mpg in my 1999 rx300..use 93 octane..change air filter with K&N filter..mostly city driving...87 octane recommended?

[TunedRX300]

Select a set of light weight wheels will reduce rotational inertia will be helpful to improve city driving mpg. Improved aero-dynamic will help reduce air drag, which is helpful to improve freeway performance.

From tire rack's helpful link Rolling Resistance

During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%.

Overcoming inertia no longer plays an appreciable role in the vehicle's resistance during steady speed highway driving. For those conditions it is estimated that driveline friction is about 15%; air drag is about 60% and tire rolling resistance represent about 25%.

[scoobie]

...

Any idea or guess how many mpg just removing the spare tire would save?  What do people think about that idea (is it worth it?)  I hear that some cars nowdays don't even come with a spare tire (they come with an inflator can.)  If the mpg saved by removing the spare tire is actually noticeable then I would consider doing it...

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I don't think this question was actually addressed by the later posts, here's my take based on my limited recollection of high school physics:

Assume the car weigh 4000 lbs, and the spare weigh 50 lbs, and that the engine converts gas into work at a constant rate. Work = mass x distance, so if mass is decreased by the factor 3950/4000, then distance can be increased by the same factor for the same amount of work.

Result: if you get 20 mpg with spare, then without spare should be 20 x 4000/3950 = 20.25 mpg.

Of course the real world is not a textbook physics problem and I'm sure there are major flaws in the assumptions above, but I think the point is clear that the increase in mpg is in the 'noise' level.