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1993 lexus ls400 gas question

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Old 05-03-11, 11:59 AM   #1
flashy5
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Default 1993 lexus ls400 gas question

ok I have 1993 ls400 , now i understand its a v8 and all that but my question I think mine goes thru gas way to quick, when i first got it was misfiring so it was going thru gas way to fast so i changed the spark plugs and spark plug wires and that made a big difference but I think my car stills goes thru gas to quick, is there anything i can do to make my car better on gas, I had a lexus sc400 and did not go thru gas that quick.
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Old 05-03-11, 12:13 PM   #2
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Do a search on "bad fuel mileage" and you'll come up with alot of ideas on how to get better mileage. But I just posted this for someone else. http://www.clublexus.com/forums/ls40...read-this.html
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Old 05-03-11, 04:07 PM   #3
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What is your gas mileage in miles per gallon? It should be in the mid-high teens at least (15-19 mpg). Are you doing mostly highway or city driving?
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Old 05-04-11, 10:01 AM   #4
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burn regular unleaded. there are several long threads on this. burn fewer dollars, even if not fewer gallons. won't cause knocking unless you do a lot of towing, real hard driving, or a lot of mountain driving. but i live outside denver and have never had knocking while driving up I-70 on regular.

also, there is an article on the "car talk" website.
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Old 05-04-11, 11:41 AM   #5
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I am not sure but a quarter of a tank barely lasts a day and i am not driving long distances
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Old 05-04-11, 04:13 PM   #6
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There are many variables that can cause bad gas mileage, so it's hard to say. If you search around, you'll find that someone on the forum improved their mileage by changing their engine coolant temperature sensor. On my 91 LS, fuel mileage increased dramatically when I replaced the original oxygen sensors.
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Old 05-04-11, 05:11 PM   #7
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Quote:
Originally Posted by flashy5 View Post
I am not sure but a quarter of a tank barely lasts a day and i am not driving long distances
Not sure? You need to get scientific about this and calculate your gas mileage over a number of tank fulls. I've recorded every gallon of fuel I've put in every car I've owned for 45 years and kept a running track of miles per gallon.

The gen 1 LS400 is not even close to being an economy car. I drove one for 13 1/2 years ending in 2003. Even on extended highway only trips, I rarely got more than 23.5 mpg and I routinely got 15-17 mpg in low speed city only driving.
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Old 05-06-11, 05:41 PM   #8
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Quote:
Originally Posted by denverdog View Post
burn regular unleaded. there are several long threads on this. burn fewer dollars, even if not fewer gallons. won't cause knocking unless you do a lot of towing, real hard driving, or a lot of mountain driving. but i live outside denver and have never had knocking while driving up I-70 on regular.

also, there is an article on the "car talk" website.
Umm... Ok? You can read as many threads as you want, but if there all full of bad information, what's the point?

The real reason why we should be using premium is because of the compression ratio, or CR, which is > 10:1, and the newer they get, the higher the compression ratio. The number that is reference on the pump is the octane rating, not news, I know. In leman's terms, octane is the resistance to detonation. So let's say you take a mid 90's 350 Chevy, it's going to be 9.0:1 compression ratio. It will squeeze the volume in the cylinder 9x smaller from where it starts at bottom dead center, or BDC to TDC. What is important about this is that this is where detonation come into play. The Chevy engine will call for 87 octane, because the more volatile gas, 87 octane will not effectively compress more than (IIRC) 10:1 CR. If you were to use premium in the Chevy engine, you wouldn't notice one bit because the extra resistance to detonation isn't required. Now, for the Lexus V8, which I believe are all at least 10:1 CR, and with VVT-i, it's even more important as the compression ratio will change per firing cycle. If you were to run 87 octane in a UZ V8, the electronics will take care of any real issues with spark timing and fuel trim, so you'll never notice the difference. However, what you don't see is that the 87 octane fuel is actually combusting before the piston reaches TDC, because the fuel to volatile to handle the added pressures of high compression ratios. Likewise, race cars often using ethanol based fuels because they have higher octane ratings, which give them the ability to make more power, while reducing detonation, knocking, and ultimately failure.

I hope that helps. Feel free to critique. As far as your basic maintenance, check tires, oil, air filter, coolant temp sensor, etc.
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Old 05-06-11, 05:41 PM
 
 
 
 
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