JCtx

Hey Umbo... but I want you to have a problem buddy!! Maybe you can go '-30'

So far Umbo has the most 'cojones' by running 20 beyond 'zero'. I'm sure Roofless will better that pretty soon. Oh, I forgot; would you mind stating your car's year? It might be a difference from earlier ones to newest.

Keep us posted gentlemen.

Umbo

I might take it 30mi beyond zero just for kicks, but I think thats still in the safe range. 48mi would leave the tank bone dry. I used to take my BMW 330 xi down to 1 gallon all the time and I don't ever remember a sputter. The only time I ran out of gas was in 1983. I was just a lame brained college kid at the time and wasn't paying attention to the gas gauge.

My SC is an '04.

loflin

I have one of the first SC430, July 2001.

The miles to go (and the gauge) are very conservative.

I habitually go 20+ miles after the blinking Low Fuel on the trip computer in the middle console. That is I have done it 30+ times.

Even then, the most I EVER remember getting into the tank at the fill up was 17.9 gallons.

JCtx

I'm down to almost empty, and so far no low fuel light anywhere. Trip computer says range=10.

As a side comment, I forgot to fuel up my MDX and my wife drove it across town. I have her so spoiled she doesn't even look at the gas gauge anymore . Checked it, and the needle was a tad below empty (past the entire red mark). Trip computer said 5 miles left. Took it to the closest one (not knowing how accurate it is), and got there with 4 miles left on the computer. Tank took 18.858 gallons, and capacity is 19.2. Only 1/3 of a gallon short of capacity. That's only 5.33 miles on average 16 mpg, and remember there will always be some fuel left in the tank after running out of fuel. I'd say that thing is accurate within a mile; impressive.

I'm probably going to fuel up the SC close to zero and see how much is left in there. You never know, and I don't want to walk

Later guys.

caraholic

Hey guys, I'm new to this forum but have been following this thread and likewise I am confused regarding the trip computer. I have a new 2004 SC I filled it up last week-end and the trip computer said my range was 277 miles and the MPG is 18.4. That calculates to 15.05 gals? I've had a trip computer on my last two cars (not Lexus) and they were always right on based on the tank size and MPG. So, doesn't this mean it's not really using the whole tank, as in, not counting the reserve? Also, even given that you can't use every drop of fuel, it still seems odd that the tank would not hold close to 19.8 gallons as specified? Am I missing something on the trip computer? This is a GREAT car, just trying to figure out how far she'll go!

tfischer

In my experience, the range given for a full tank is, as you have observed, very low.

I'm not sure why, since I don't know what factors the computer uses, but as you get down to a quarter tank or so it becomes more accurate, maybe because it takes into consideration past or current speed.

This has always confused me, because the same computer gives very, very accurate reads on MPG, which I have checked several times the old fashioned way.

For most people it's not really a problem since who drives it way down to the "E" anyway? Also, when you get really low, you get a red light on the dash at the gas gauge as an additional reminder.

Happy motoring.

PS: I would think that the tank capacity given in the specs is very accurate.

caraholic

Well, sounds like a great opportunity to do some investigation. I have been keeping it over a 1/4 until now. I think I'll wait until it gets close to 0 and see how many miles I actually got since the fillup, and how many gallons it takes to fill up the tank, etc. Thanks for the response.

JCtx

I'm also down there. The orange light just lit right before empty, with the trip computer showing a range of 10 miles. Way too late IMHO. Trip computer is down to 7, and needle is pointing exactly at the beginning of the empty line.
I won't drive it beyond zero because I don't know the car, but will try to refill it exactly at zero and see how many gallons it takes. And what kind of range vs mpg I get. The last MPG figure should be multiplied times tank capacity if full, giving a full range. I'll also make sure I top off the tank until I see the gas, to avoid underfilling it. I never do that but will do it this time for the sake of science

Car is 3 weeks from its first anniversary and 1,628 miles on the odo. Will try to at least put 2K; this is ridiculous.

Later guys.

Umbo

I don't see the big mystery here. When the computer says zero "low fuel", there are still 2.5 - 3 gallons of gas in the tank. I've already done the experiment several times. It is absolutely no big deal to drive the car 20 miles or even more beyond the computer's zero reading. At 20 miles beyond zero, there are still 2 gallons of gas in the tank. I have done it several times without a sputter. I don't know why the computer is so conservative. I guess Lexus wants to make sure that no one ever comes close to running out of fuel.

My SC is an '04.

tfischer

I must agree with Umbo.

The warnings are a bit premature, as in many cars, I would suspect, but for most purposes are close enough to acheive the intended effect.

I remember when the original VW didn't even have a gas gauge. That was much more fun than crabbing about still having 20 extra miles after the third low fuel warning goes off.

JCtx

Using logic, you 2 guys must be right. Having the 'low fuel' warning amber light lighting up with 10 miles remaining (on the computer) doesn't make any sense, does it? Although needle is right on empty now.

I just want to see how many gallons my car takes in, and compute the difference. I'm sure it'll be like you said, but I honestly don't want to call roadside assistance for such stupidity
Will fuel up today, and report my findings.

Good day people.

tfischer

"Using logic . . ."

Since when did we have to start using logic here?

Using logic often makes my head hurt. Can't we just continue to fire off replies based on whim, conjecture, surmise and supposition?

Please.

Maybe just a little?

Roofless

After starting to stall again with 10 miles left on the computer, and noting my car took 15.8 gallons to fill, I had my car in for service. They replaced a fuel filter and I'm now 20 miles below the Low Level warning. So my car is normal with the standard stupidly oversized and hidden reserve.

Umbo was right on this whole time.
I'm very sorry for the confusion.

If you're ever in Baker, CA, avoid the Texaco station. I believe they add lizard feces to their fuel...

Carpe Diem

If you go waaaaay back, I think all petroleum based fuels contains lizard feces, probably from very large lizards.

George

JCtx

Okay guys, here's my experience on my refueling tonight:

Pulled in the gas station (brand new one, with brand new pumps) a mile after trip computer reached '0', at which time it displayed 'low FUEL'.

The total REAL mileage for the tank was 334.
Range after filling up read 310 (hmmmm).
Average MPG on the trip computer read: 19.3.
REAL average MPG (334/18) was 18.55

Tank took exactly 18.0 gallons (capacity is listed at 19.8).

Bottom line? Computer is OPTIMISTIC on fuel economy, and PESSIMISTIC on range. Weird, huh?

My tank took more than yours, but still 1.8 gallons short of capacity. Not all that fuel is usable for sure, but I'd guess 0.8 gallon is. Remember fuel pump is cooled by fuel, so pick-up point should be above it to completely cover it. The extra 0.8 gallon still leaves a 15-mile 'extra reserve'. After that you're on fumes.

Needle was at the bottom edge of the empty line. I'm okay with the gauge. I'm also okay with the low fuel warning lighting up very close to empty. On my other cars it lights up at 1/8, and that sucker is BRIGHT.

Later guys.