Gas Tank Shrinking?

[Mr.patel]

Last year my 05 lexus es330 would get 400 miles to a full tank. Since then every time i filled up my tank, the range would go down. Now about a year later my car will get 280 miles to a full tank. I reset my trip after filling my tank once just to check how many miles i get and with a full tank i still get 280 miles. Anyone know why this is happening? Please!!! help me out

[lenore]

Might be the formulated gasoline that our wonderful government has thrown on us...If it has ethonol mileage can decrease 10%

[pj8708]

Last year my 05 lexus es330 would get 400 miles to a full tank. Since then every time i filled up my tank, the range would go down. Now about a year later my car will get 280 miles to a full tank. I reset my trip after filling my tank once just to check how many miles i get and with a full tank i still get 280 miles. Anyone know why this is happening? Please!!! help me out

It is doubtful that a gasoline mixture would account for a drop of 120 miles difference. Even using a blend of 10% ethanol (which I run all the time) and accounting for a 10% mpg difference that Lenore is suggesting, that would only account for 40 miles off of the 400 miles you say you originally were getting.

Take you car to the dealer FIRST. Explain the problem and see if they can provide some insight before you go swapping out parts or trying home made remedy's. A drop in mpg of this magnitude, if your numbers were correct in the beginning, is significant.

I had an 05' ES330 and when I filled up, the range meter would always read about 280-295. That is a bout the range of miles I would get until time to fill.

[1990LS400]

The first thing to do is to manually calculate and record your fuel mileage over eight to ten tanks of fuel.

Has anything changed? Are you carrying a boat anchor in the trunk that you didn't carry last year? Are you driving shorter distances, doing more stop and go driving, carrying more passengers, etc.? Not that it is going to make a huge difference but are your tire pressures at the correct level?

[SW03ES]

Yes, manually calculate. When you fill up, reset the trip odometer. Wait until the tank reads empty (ignore the trip computer) and look at the mileage.

The trip meter's estimated range mileage is based off a running average over time of your fuel economy. If you have been mainly driving around town...that average goes down. The computer calculates the average mileage based on the estimated number of gallons in the tank and that average. So...17 gallons in the tank...a 280 mile range is an average of 16.47 MPG. Not an unusual city mileage for that car. 400 mile range would be 23.5 MPG. More of a highway mileage.

So, in short...its incredibly inaccurate unless you drive exactly the same way all the time. For instance on my 2010 (which has a better range estimation IMHO) when I bought it a full tank showed a range of 375 miles. Now, I drive a mixture of highway and city, some of it is street to street with a lot of startups and shutoffs when showing houses, so my average MPG on a regular basis isn't great. In the 7 months or so I had it I had taken a couple 3 hour trips but with traffic and such, my range was showing 320 miles or so after a fillup.

Last month I took a 5.5 hour open highway trip where I was able to set the cruise on 80 and just drive. My 2010 will get 31MPG or so on the highway.

When I filled the car up after that trip...the estimated range was 415 miles. nearly 100 miles more than was previously estimated. Now...driving on the highway I probably was able to go 500 miles on one tank...but in my normal driving thats not the case obviously because the MPG is less.

So what has changed is simply the data the computer is using to estimate the range, not the actual range. Now that I'm home and back to my normal driving habits the range is decreasing with each fill-up again. Down to 380 the last time.

So what is decreasing is your computer's data used to compute the range...not the range.

[pj8708]

Yes, manually calculate. When you fill up, reset the trip odometer. Wait until the tank reads empty (ignore the trip computer) and look at the mileage.

The trip meter's estimated range mileage is based off a running average over time of your fuel economy. If you have been mainly driving around town...that average goes down. The computer calculates the average mileage based on the estimated number of gallons in the tank and that average. So...17 gallons in the tank...a 280 mile range is an average of 16.47 MPG. Not an unusual city mileage for that car. 400 mile range would be 23.5 MPG. More of a highway mileage.

So, in short...its incredibly inaccurate unless you drive exactly the same way all the time. For instance on my 2010 (which has a better range estimation IMHO) when I bought it a full tank showed a range of 375 miles. Now, I drive a mixture of highway and city, some of it is street to street with a lot of startups and shutoffs when showing houses, so my average MPG on a regular basis isn't great. In the 7 months or so I had it I had taken a couple 3 hour trips but with traffic and such, my range was showing 320 miles or so after a fillup.

Last month I took a 5.5 hour open highway trip where I was able to set the cruise on 80 and just drive. My 2010 will get 31MPG or so on the highway.

When I filled the car up after that trip...the estimated range was 415 miles. nearly 100 miles more than was previously estimated. Now...driving on the highway I probably was able to go 500 miles on one tank...but in my normal driving thats not the case obviously because the MPG is less.

So what has changed is simply the data the computer is using to estimate the range, not the actual range. Now that I'm home and back to my normal driving habits the range is decreasing with each fill-up again. Down to 380 the last time.

So what is decreasing is your computer's data used to compute the range...not the range.

I see you've learned well, everything I've been teaching you!! LOL!!! What a great synopsis for all of us. I did not know that the Range indicator was influenced by the mpg factor. The tank avg. obviously. This explains the phenomena with my ES330.

I hope this solves the persons problem and thanks for the well done lesson.

Paul

[Mr.patel]

I appreciate everyones support and help on this issue. This solves a lot of questions for me and helped me out tremendously! Thank you all!

[SW03ES]

No problem! Welcome to the club!