Full tank range!

baviaannl · October 21, 2018

I've given the car it's first full tank as i have a European road trip starting in the morning. I filled the tank with £77 of petrol although the computer is telling me I have a range of 314 miles!

I was kinda expecting more than that, the Lexus has a bigger fuel tank than my previous (big heavy CRV) and I could get more mileage for less.

Not sure if I should be worried here?

Shahpor · October 21, 2018

I wouldn't worry about what the computer is telling you. Unless the car is having problems, which usually involves symptoms like rough running and smoke, you should do much better than that, especially if you are on the motorway.

You could just reset all the counters and trip meters just to see how many mpg it actually does.

Rabbers · October 21, 2018

The range forecast by the OBC is based on the total distance travelled with the amount of fuel contained in the tank after the previous re-fuelling. In

order for full-tank forecasts to be realistic or near-realistic, re-fuellings should, in my experience, preferably be fairly substantial one to the next. Unless

something is wrong, you'll almost certainly find the forecast range reading satisfactorily higher after a second successive full tank.

NemesisUK · October 21, 2018

I thought range was determined by multiplying the current MPG by the remaining tank content?

The forecast range can change dramatically if you change driving style i.e. go from town driving to motorway, or start flooring it, the range will drop rapidly..

baviaannl · October 21, 2018

Well, I have hundreds upon hundreds of miles over the next few days, 80% motorway so will be a good experiment.

Rabbers · October 21, 2018

46 minutes ago, NemesisUK said:

I thought range was determined by multiplying the current MPG by the remaining tank content [?]...

You’ve put it more correctly than I did. If the tank has just been filled to the top the forecasting basis can only be the last known mpg, which until the variables such as style and types of road come into play, as they almost immediately will, is what the OBC believes you will maintain.

Alecis250 · October 24, 2018

On 10/21/2018 at 1:52 PM, baviaannl said:

I've given the car it's first full tank as i have a European road trip starting in the morning. I filled the tank with £77 of petrol although the computer is telling me I have a range of 314 miles!

I was kinda expecting more than that, the Lexus has a bigger fuel tank than my previous (big heavy CRV) and I could get more mileage for less.

Not sure if I should be worried here?

That doesn't sound too bad to me but I make alot of short journeys. Hopefully you will be pleasantly surprised by the range you achieve!

Tyre Tread · October 26, 2018

I am getting a genuine 40mpg brim to brim calcs using an app over the last 18 months. That's mostly motorway commuting of 44 miles each way to work, about 38 of which is motorway.

Summer gets me 42 and winter about 38. The temperature really affects the overall mpg as does sitting in traffic and lots of local runs.

I tend to stick the cruise on at 75 on the motorway..

Expect around 500 ish miles on a tankful on a motorway run as long as you don't hammer it.

baviaannl · October 27, 2018

Got back yesterday, I managed 460 miles on the first tank, averaging 36/7 miles to the gallon, I could have managed 40MPG although I did enjoy myself 😄

On the way back, the 2nd fill averaged 36MPG, got a quarter tank left with 420 miles recorded so will prob do about the same.

More than happy with that 🙂

Tyre Tread · October 27, 2018

4 hours ago, baviaannl said:

Got back yesterday, I managed 460 miles on the first tank, averaging 36/7 miles to the gallon, I could have managed 40MPG although I did enjoy myself 😄

On the way back, the 2nd fill averaged 36MPG, got a quarter tank left with 420 miles recorded so will prob do about the same.

More than happy with that 🙂

Was your MPG based upon what the trip computer told you? Be aware the computer is about 7% optimistic on mine.

Rabbers · October 28, 2018

17 hours ago, baviaannl said:

Got back yesterday, I managed 460 miles on the first tank .... the 2nd fill ...will prob do about the same.

So, then, in relation to your OP, did you look at the range forecast after the second fill to see if it more or less came in line with the actual miles you achieved with the first?

I must say that your mileage based on my own experience with two IS250s, the last of which was MY2010, is pretty good. I used to think I was doing well if I could squeeze 650km = 400miles out of a tank on long motorway drives.

Linas.P · November 1, 2018

my best was ~580 miles (~900km) from tank on fairly fast roads 90-100MPH. But that is pretty much most you could expect as I filled like 62L in the end, meaning it was half way through reserve.

On 10/27/2018 at 8:41 PM, Tyre Tread said:

Was your MPG based upon what the trip computer told you? Be aware the computer is about 7% optimistic on mine.

Cannot agree - I have found IS250 MPG reading to be dead accurate comparing vs. brim to brim, the newer hybrids are wildly optimistic.

Tyre Tread · November 2, 2018

20 hours ago, Linas.P said:

my best was ~580 miles (~900km) from tank on fairly fast roads 90-100MPH. But that is pretty much most you could expect as I filled like 62L in the end, meaning it was half way through reserve.

Cannot agree - I have found IS250 MPG reading to be dead accurate comparing vs. brim to brim, the newer hybrids are wildly optimistic.

And of all the cars I've had with trip computers I've never had one that gave a correct MPG reading, they have ALL, without exception, been optimistic. From A Jazz to and XF S Jag. Every. single. one!

Linas.P · November 2, 2018

for 4,5 years I am doing brim to brim on IS250 and difference is ~ +/-1%.... should I pull out my spreadsheet now?

The trip computer range prediction maybe? That is obviously just a guesstimate based on last tank... but the tank MPG you get at the end of the tank is dead accurate. I always fill full tank until it clicks (twice for good measure) and I always run it to completely empty... I am not sure maybe that helps, maybe if you refill half way then it gets incorect?

Tyre Tread · November 3, 2018

By all means put up your spreadsheet. If I can figure out how I'm happy to put up the figures over the last 1.5 years and 25K miles from the "Mycars" app using brim to brim calcs.

You may be lucky and have an accurate calculation on your car but it will be a rare beast.