Gas Mileage

[laney94]

I recently added a fuel system cleaner to my nearly empty gas tank and filled her up. I immediately noticed more power and running great. But now I have lost about 60 mpg per tank of gas!! What could cause this to happen??? I had a hesitation at about 50mph that seems to have subsided since this treatment, but I'd trade that for my former 20+mpg! Thanks for any suggestions.

Okay, to be more clear - it was GumOut fuel system cleaner that I used. Is there a problem with using this stuff?

[curiousB]

I recently added a fuel system cleaner to my nearly empty gas tank and filled her up. I immediately noticed more power and running great. But now I have lost about 60 mpg per tank of gas!! What could cause this to happen??? I had a hesitation at about 50mph that seems to have subsided since this treatment, but I'd trade that for my former 20+mpg! Thanks for any suggestions.

Okay, to be more clear - it was GumOut fuel system cleaner that I used. Is there a problem with using this stuff?

Fuel problems fixed by these cleaners are usually to cure fuel restriction or starvation. As such its hard to imagine why mileage would go down. Could be an unrelated problem nothing to do with the cleaner you used. If the car is running well then you should probably perform a very accurate MPG test. Fill tank up at a level filling station, drive car to near empty and then refill at the same station and same pump. Then compute MPG.

[laney94]

I recently added a fuel system cleaner to my nearly empty gas tank and filled her up. I immediately noticed more power and running great. But now I have lost about 60 mpg per tank of gas!! What could cause this to happen??? I had a hesitation at about 50mph that seems to have subsided since this treatment, but I'd trade that for my former 20+mpg! Thanks for any suggestions.

Okay, to be more clear - it was GumOut fuel system cleaner that I used. Is there a problem with using this stuff?

Fuel problems fixed by these cleaners are usually to cure fuel restriction or starvation. As such its hard to imagine why mileage would go down. Could be an unrelated problem nothing to do with the cleaner you used. If the car is running well then you should probably perform a very accurate MPG test. Fill tank up at a level filling station, drive car to near empty and then refill at the same station and same pump. Then compute MPG.

[laney94]

I recently added a fuel system cleaner to my nearly empty gas tank and filled her up. I immediately noticed more power and running great. But now I have lost about 60 mpg per tank of gas!! What could cause this to happen??? I had a hesitation at about 50mph that seems to have subsided since this treatment, but I'd trade that for my former 20+mpg! Thanks for any suggestions.

Okay, to be more clear - it was GumOut fuel system cleaner that I used. Is there a problem with using this stuff?

Fuel problems fixed by these cleaners are usually to cure fuel restriction or starvation. As such its hard to imagine why mileage would go down. Could be an unrelated problem nothing to do with the cleaner you used. If the car is running well then you should probably perform a very accurate MPG test. Fill tank up at a level filling station, drive car to near empty and then refill at the same station and same pump. Then compute MPG.

Will do Curious B. Actually I don't trust my fuel gauge, so I reset my trip odometer after every fillup and I know at about 360 miles, the fuel light would come on. Now it's coming on at about 300 miles. I thought maybe it was still the fuel gauge, but to fillup, it took 19 gallons which it always has when the light comes on - thus the 60 miles lost. I'll do an accurate mpg check to be sure. I've owned this car for 16 years (since new) so I know it very very well. This is not in its character at all. Thanks for your response.

[billydpowell]

maybe it has been starving for fuel (running lean) until you cleaned it out, and now it is normal????

just a thought.....

[landar]

I have the opposite "problem". After replacing the timing belt, water pump and thermostat, my Lex has been getting an

average of 25 MPG vs. the 23 MPG(combined city/country driving, my standard work route..not highway) it was getting before. I do not understand it. The engine does run a bit warmer now with the new thermostat(temp. gauge needle reads slightly higher).

However, it has only been two tanks and I am going by the computer average reading. Still there is a noticeable difference that is puzzling.

[eatingupblacktop]

I have the opposite "problem". After replacing the timing belt, water pump and thermostat, my Lex has been getting an

average of 25 MPG vs. the 23 MPG(combined city/country driving, my standard work route..not highway) it was getting before. I do not understand it. The engine does run a bit warmer now with the new thermostat(temp. gauge needle reads slightly higher).

However, it has only been two tanks and I am going by the computer average reading. Still there is a noticeable difference that is puzzling.

My guess is that your new stat is not opening as much as the old one and the increase in coolant temp is causing the ecu to lean out the fuel mix just enough that the O2 sensors don't factor in. Maybe you've increased the tire pressure just enough to make the diff.

[eatingupblacktop]

... the fuel light would come on. Now it's coming on at about 300 miles.

Laney, Id be careful about using that fuel light to tell you when to refill. It's there as a low fuel level warning and should be used for that purpose only. I'd stay above the quarter tank level in the summer and half tank level in the winter. Personally, I keep the fuel full all the time in the winter. The less fuel in your tank, the more condensation you get. You can't see the fuel that's going into your tank and all the crud from the bottom of the stations tanks that might be going in right along with it. When you get to the warning light, you're sucking up whatever crap is at the bottom of your tank. Besides plugging up your filter, if there's enough water down there you risk freezing the fuel lines in the winter. Last thing I want to happen when there's a blizzard about and I'm still 25 miles from home!

[landar]

My guess is that your new stat is not opening as much as the old one and the increase in coolant temp is causing the ecu to lean out the fuel mix just enough that the O2 sensors don't factor in. Maybe you've increased the tire pressure just enough to make the diff.

Yeah, the higher operating temp might be having an effect, but an 8% increase in MPG? Dont get me wrong, its a good "problem" to have.

I want to write it off as an imagination on my part. Maybe I am driving it easier(dont want that new Tbelt to break ). Or maybe the AC is

now off (which it is, winter and all). Tire pressure might make a very slight improvement but mine were not low and I did not add air.

Well, time will tell. With each tank so far, the MPG has remained high. I am anxious for a long highway trip to see what it is doing in that department.

I am inclined to think that the Tstat is running slightly higher and the engine more efficiently. Best $15 I have ever spent.

In any case, that 1uz-fe is an amazing engine. Tell you a funny story. I was working on the Lex with the Tbelt/water pump replacement and my wife's

98 Chrysler(with 3.8L) water pump went out(I think it was jealous). So, I had to momentarily drop the Lex and switch over to the Chrysler. What a contrast. I go from a sophisticated machine to what looks(to me, anyway) like a tinker toy! An easy to work on tinker toy, mind you, but a "toy" (comparatively speaking) nonetheless. ;)

[killerFatty]

I have noticed though that I have about 5 gallons left when the gas light comes on. On other cars I've drove it doesn't come on untill there is only about two gallons left. With 5 gallons in the tank I wouldn't be that concerned about the fuel filter getting clogged. That is of course if you dont drive another 50 miles after the light comes on. I also totally agree that you should keep a full tank in the winter. It not only keeps you form worrying if you get stranded, but it also puts some more weight over the rear tires which will help with traction.

[eatingupblacktop]

In any case, that 1uz-fe is an amazing engine. Tell you a funny story. I was working on the Lex with the Tbelt/water pump replacement and my wife's

98 Chrysler(with 3.8L) water pump went out(I think it was jealous). So, I had to momentarily drop the Lex and switch over to the Chrysler. What a contrast. I go from a sophisticated machine to what looks(to me, anyway) like a tinker toy! An easy to work on tinker toy, mind you, but a "toy" (comparatively speaking) nonetheless. ;)

You got that right! As you say, it becomes really obvious when you have a different make sitting right beside the LS, like I do with my Volvo. In my case it's not so much a tinker toy as it is a PITA in many ways. The B280F in my Volvo is a PRV collaboration. Pugeot, Renault and Volvo hashed it out and came up with what is basically a V8 with 2 cylinders cut off. The 90 degree cylinder banks and uneven firing sequence make for a lumpy idle which can't be corrected. Placement of some parts like a coolant hose behind the intake manifold requiring the removal of the manifold just to replace it, makes you wonder what the designers had in mind when they created this placement. Cam wear was a big problem because the exhaust valves shared a single lobe, while inlet valves had a lobe each and they were made from a soft alloy. It's engine design by committee. Always a crapshoot. Not to mention the horrors of the interior - trim/switches/fading colors/cheap plastic peices, etc. The best part and perhaps only good part of this car were the seats. Even though the leather was not very durable, the seats were and still are among the most comfortable I've sat in. Lexus could learn something here.

The 1UZ-FE on the other hand (and some may not know this) was designed as an oversquare, 6 bolt racing engine and was based on CART and IRL engine design. As a result it's a pleasure to do WOT runs. It loves going into the higher revs, making all the right sounds and stays smooth all the way up!. It's also one of the smoothest engines I've driven. The ad Toyota ran when they introduced the LS, showing the pyramid of wine glasses sitting on the hood with the engine running, pretty much says it all. Every time I work on this engine, I'm impressed with the quality of the materials Toyota used. They're just plain superior to most other manufacturers. Engines like the 1UZ-FE actually motivate you to maintain them. Nevertheless, I've been delaying doing an oil change while it's garaged for the winter because the first thing I want to do after one is take her for a spin.:whistles:

[landar]

The 1UZ-FE on the other hand (and some may not know this) was designed as an oversquare, 6 bolt racing engine and was based on CART and IRL engine design. As a result it's a pleasure to do WOT runs.

I bought my LS because I had heard that they were nice cars and I could not resist the bargain of a nice, clean used luxury car. However, what I did not know about, was

the engine and acceleration. The first time I mashed my foot on the accelerator, I got the surprise of my life! There was a slight hesitation then the car just took off.

Not Corvette fast but much faster than what I was expecting. That engine just winds up and pounces. Neat sound too. Could be addictive. :D

[92ls forhundo]

The 1UZ-FE on the other hand (and some may not know this) was designed as an oversquare, 6 bolt racing engine and was based on CART and IRL engine design. As a result it's a pleasure to do WOT runs.

I bought my LS because I had heard that they were nice cars and I could not resist the bargain of a nice, clean used luxury car. However, what I did not know about, was

the engine and acceleration. The first time I mashed my foot on the accelerator, I got the surprise of my life! There was a slight hesitation then the car just took off.

Not Corvette fast but much faster than what I was expecting. That engine just winds up and pounces. Neat sound too. Could be addictive. :D

interesting, i have noticed a drop in fuel economy lately too, though i live in california, and it seems they constantly change the formulations of our gas here, tires are inflated, dont know why this time...sometimes there are "bad batches of gas" that are out there, and those seem to burn up quicker somehow...

as to the corvette/ls400 comparo, believe it or not, the original ls 400 had better drag coefficient numbers than corvettes of the same era!

[laney94]

... the fuel light would come on. Now it's coming on at about 300 miles.

Laney, Id be careful about using that fuel light to tell you when to refill. It's there as a low fuel level warning and should be used for that purpose only. I'd stay above the quarter tank level in the summer and half tank level in the winter. Personally, I keep the fuel full all the time in the winter. The less fuel in your tank, the more condensation you get. You can't see the fuel that's going into your tank and all the crud from the bottom of the stations tanks that might be going in right along with it. When you get to the warning light, you're sucking up whatever crap is at the bottom of your tank. Besides plugging up your filter, if there's enough water down there you risk freezing the fuel lines in the winter. Last thing I want to happen when there's a blizzard about and I'm still 25 miles from home!

Well, I think I've found my problem with the fuel economy question... I filled her up and set the trip gauge then drove to work the next morning in freezing temps. The backlight on my dash is out and it takes a bit of warming up for the needles to spring into action and light up, as well as the temp and odometer readings. Well, when they did light up, the trip was at zero miles - it had not been working for the past 15 miles or so. Guess my mpg okay after all - it's my odo that's off. Geeeez.