LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Gas Mileage Problems...TOOO LOW!

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Old 01-26-08, 07:16 AM
  #31  
93LSexy
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Originally Posted by Bali26
Also if your engine is not getting hot enough, u will get bad mileage. Ecu switches over to closed loop only when its gets operating temp. (from article above)

My temp gauge never goes over 1/4 mark. ( maybe fan is always running instead of shuting off, or maybe thermostat )
BINGO!!! that's something I noticed also. I don't know the normal operating temperature in relation to the temp gauge needle, but I do know that it suppose to warm up and stay at the normal operating temperature by shutting off the fan or close the thermostat. My car warms up to the 2nd marker counting from the bottom and as soon as I start to drive, it will go down to midway of 1st and 2nd mark.

now if the car is sensing the temp is low, shouldnt it shut the fan off and close the thermostat? i think its good for the engine to run cool, but in the winter, it never warms up!!! should I change my thermostat? maybe it's stuck in the full open position??
Old 01-26-08, 07:20 AM
  #32  
93LSexy
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so next question...

does Gen1.5 have fan clutch? or it runs all the time. because mine runs the second I turn the car on.
Old 01-26-08, 11:13 AM
  #33  
Bali26
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Bump

and what controls fan's operation?

is it supposed to shut off?

how to diagnose?

I hate when fan runs at -10 degree weather start up!!
Old 01-26-08, 06:05 PM
  #34  
docdgt@com
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A note on mileage. I have a '97 Gen II; on highway driving with a warm engine (and 87 octane) it will yield 23 - 27 mpg, depending on conditions and speeds. In town, with a colder engine, 17 - 19.

I can tell no difference between 87 and 93, and I have been using 87 for over a year with no ill effects or problems. I am also light footed on the accelerator.
Old 01-26-08, 10:24 PM
  #35  
jcrome04
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I've never put less than 93 in this LS or my old LS. If the engine requires "Premium" then I put premium. If you own a Lexus...whats the problem with $0.20 more a gallon? $2.00 a tank?.. nothing big.

Better performance and mpg's. Smoother operation. I'm not saying it's anything drastic enough to write home about but there is a difference that I've noticed!
Old 01-27-08, 09:24 AM
  #36  
GKLCPA
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Originally Posted by jcrome04
I've never put less than 93 in this LS or my old LS. If the engine requires "Premium" then I put premium. If you own a Lexus...whats the problem with $0.20 more a gallon? $2.00 a tank?.. nothing big.

Better performance and mpg's. Smoother operation. I'm not saying it's anything drastic enough to write home about but there is a difference that I've noticed!
Actually, that difference is more like $ 5 a fill-up!

Prior to the last couple of weeks, I was burning premium and decided to give regular a shot just to see what would happen. I can barely tell the difference between power delivery and there's no difference in mpg. I probably just burn premium once a month or so.
Old 01-27-08, 01:43 PM
  #37  
jcrome04
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22.5gal X $3.17 (Regular at Chevron here) = $71.325
22.5gal X $3.37 (Premium at Chevron here) = $75.825

So if we need to get really technical... It's a difference of $4.50

But in reality we don't run our tanks 100% dry, So the average driver probably fills up 18-20gal. So lets just say 19gal fill up.

19gal x $3.17 (reg) = $60.23
19gal x $3.37 (prem) = $64.03

So in reality it's about a difference of $3.80

For example I also know that it's ok to go about 5,000 miles on an oil change, but most people change it around 3,000. So why not spend the extra $3.80 a tank. For factory recomended fuel. Which may not DRASTICALLY improve performance or mpg's but there is a SLIGHT increase, and will also reduce knocking and boost smoothness, and have the engine working at 100% instead of 95%

This will be interesting:
Let's also just say you fill up once a week every year.

(using the 19gal reference)
$60.23/ week X 52 weeks = $3131.96 a year
$64.03/ week X 52 weeks = $3329.56 a year

So technically the difference between regular and premium a year is $197.60

Difference In Years
$197.60 X 5 years = $988.00
$197.60 X 10 years = $1976.00

So If you're filling up once a week for 10 years thats about $0.541 EXTRA every day!!!

Money Spent on Gas In Years
Regular
5 years = $15659.80
10 years = $31319.60

Premium
5 years = $16647.80
10 years = $33295.60


So it does add up in the long run but personally I'm just one of those guys that loves his car and wants the best of the best of the BEST for his car!

Hahaha I think I took a few breaths during that!

Last edited by jcrome04; 01-27-08 at 02:05 PM.
Old 01-27-08, 05:17 PM
  #38  
jcrome04
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A little more info...quoted from others...
--------------------------------------------------

"ecu was programmed to work within certain boundaries with high octane fuel. putting lower octane fuel puts more strain on all engine components thus shortening a cars life.
when you buy a luxury car you should expect to put a premium gas into it."
-VMF

"It is an ability to resist preignition(resulting in knocking)."
-aarman4

"I don;t mind running 87 octane ONLY WHEN I NEED TO as long as I do not "punch it" or raise the RPM too high, as 87 rated octane will usually preignite under the conditions that the 1uzfe will subject it to(high-ish compression). It should run just fine on 87 if you never truly step on the gas hard, and drive really easy, but like I said, the manufacturer wants 91, so thats what she gets whenever I fill up if it's available."
-aarman4
Old 01-27-08, 06:47 PM
  #39  
GKLCPA
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JC,

Why are you running around starting trouble about the type of gas people use? You couldn't keep this over at Club Lexus could you? Nooo, you had to involve some other people by posting this over at Lexusowners Club.

Look, I don't care if it's only 50 cents a day less. If it means so much to the oil companies to charge it, then it means just as much to me to keep that 50 cents in my pocket.

That money adds up. I could buy something with those savings. I'm not prepared to say what it is I would buy right now, but it would be something.






Originally Posted by jcrome04
22.5gal X $3.17 (Regular at Chevron here) = $71.325
22.5gal X $3.37 (Premium at Chevron here) = $75.825

So if we need to get really technical... It's a difference of $4.50

But in reality we don't run our tanks 100% dry, So the average driver probably fills up 18-20gal. So lets just say 19gal fill up.

19gal x $3.17 (reg) = $60.23
19gal x $3.37 (prem) = $64.03

So in reality it's about a difference of $3.80

For example I also know that it's ok to go about 5,000 miles on an oil change, but most people change it around 3,000. So why not spend the extra $3.80 a tank. For factory recomended fuel. Which may not DRASTICALLY improve performance or mpg's but there is a SLIGHT increase, and will also reduce knocking and boost smoothness, and have the engine working at 100% instead of 95%

This will be interesting:
Let's also just say you fill up once a week every year.

(using the 19gal reference)
$60.23/ week X 52 weeks = $3131.96 a year
$64.03/ week X 52 weeks = $3329.56 a year

So technically the difference between regular and premium a year is $197.60

Difference In Years
$197.60 X 5 years = $988.00
$197.60 X 10 years = $1976.00

So If you're filling up once a week for 10 years thats about $0.541 EXTRA every day!!!

Money Spent on Gas In Years
Regular
5 years = $15659.80
10 years = $31319.60

Premium
5 years = $16647.80
10 years = $33295.60


So it does add up in the long run but personally I'm just one of those guys that loves his car and wants the best of the best of the BEST for his car!

Hahaha I think I took a few breaths during that!
Old 01-27-08, 09:11 PM
  #40  
Bali26
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So.....I supposed talking about fan operation mechanism is out of the question?
Old 01-27-08, 10:35 PM
  #41  
jcrome04
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haha causing trouble??? I just want to educate people on their misguided views on 87 octane fuel in an engine REQUIRING 91 octane fuel..

but to all their own i guess!!
Old 01-27-08, 11:21 PM
  #42  
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its only educating as long as you respect others ideals.

there have been studies that support both sides, so theres no real point in arguing over it.
Old 01-28-08, 08:54 AM
  #43  
93LSexy
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Originally Posted by Bali26
So.....I supposed talking about fan operation mechanism is out of the question?
Bali,

It seems everyone is too involved in counting pennies than finding the root of their poor gas mileage so they can fix it and go back to using premium which is REQUIRED and GOOD for the car!

I love how people like to play engineer and ignor what the manufacture states. Coming from being a Mechanical Enginner, which is what I am, I personally think those people are just plain dumb. If an engineer states a requirement, that is because it is REQUIRED, not an option, not a luxury, not do it when you feel like it or have the money for it!!! IT IS A PURE REQUIREMENT!!! if not, then we would not put BIG signs on the dash by the fuel gauge and on the gas cap and inside the gas lid and in the INSTRUCTION MANUAL!!!
Old 01-28-08, 10:54 AM
  #44  
19psi
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guys, the only reason to use premium fuel is for maximum performance/horsepower out of the engine. no other reason. fuel mileage will not change.

you can use 87 every day until you sell the car and it will run fine. you just won't be making the full hp as advertised. you'll never even notice either unless you go full throttle to redline on a frequent basis. at part throttle low load, 87 makes as much power as 93. only at full load would the 87 cause pre ignition and the ecu retard timing.
Old 01-28-08, 01:51 PM
  #45  
93LSexy
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Originally Posted by 19psi
guys, the only reason to use premium fuel is for maximum performance/horsepower out of the engine. no other reason. fuel mileage will not change.

you can use 87 every day until you sell the car and it will run fine. you just won't be making the full hp as advertised. you'll never even notice either unless you go full throttle to redline on a frequent basis. at part throttle low load, 87 makes as much power as 93. only at full load would the 87 cause pre ignition and the ecu retard timing.

ok...that's correct in it's own way. But then why would you buy a premium car that requires premium fuel and give it regular? Being cheap? that puzzles me. Would you go buy a Ferrari and put 87 octane in it just because it will run fine as long as you don't redline it???


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