Excessive petrol consumption?

[Lex_utor]

I have been noticing that my petrol consumption seems to be up lately. Granted, it's high summer and I'm driving always with the AC on. But still. And it seems to be getting worse. Now I have had my fuel tank replaced recently (see thread here: 

I was wondering if there is anything they could have messed up which could be causing the car to use more petrol? Could be just all a coincidence. But I put half a tank of petrol and now 130km later the computer is saying I have 49 km left. Before that, the first tank I used after replacing the tank didn't even last 500km. Or is this poor mileage expected with the IS250? 

[Spock66]

2 minutes ago, Lex_utor said:

I was wondering if there is anything they could have messed up which could be causing the car to use more petrol?

The obvious thought would be is there a leak eg loose hose etc, but normally that would be obvious just from a strong petrol smell.

Maybe the fuel tank level sensor was not correctly installed, so your half tank may not actually be a half tank?

[eleveneleven]

Have you checked your brake calipers recently? 

Calipers are known for sticking which effects the wheel rotation and can end up using more fuel. Check your tyre pressures too. 

It could just be your driving, 500km is about 310 miles. I get about that from a full tank if a majority of my driving is short journeys. 330 miles (530km) seems to be the average for me driving steadily with a mixture of short and long journeys.

[Linas.P]

Really depends on what driving you doing. Over many miles of ownership I had as high as 44MPG (5.3L/100km) and as low as 18MPG (13.1/100km), average being ~28MPG. So with ~52L in fuel tank it is somewhere between 396km and nearly a 1000km if you can find the road long enough and quiet enough to cruise at 100km/h for 10 hours.

One thing I would advise - if you trying to see real fuel efficiency, then don't refill half-tanks. Fill full thank, reset trip and drive until range is 0 and you can even drive another 30-50km easily. Then refill until it clicks, see how much you were able to fill and then check what was your trip, this is so called "brim-to-brim" measurement and that is the only accurate way to tell how much fuel your car is consuming. Repeat 3-4 times and see what you are averaging. The only time fuel gauge is accurate is when your engine cut-out and it indicates "Empty", and when you fill full-tank and it shows it "Full". Anything in between is indicative at best, especially on Japanese cars from 90's and into late 2000's the last quarter on the gauge does not exist, you put full tank and drive 200km and it is still indicates full, then after another 100km it is 3/4, after another 100km it is half, and after another 100km it says you have 20km left until refill 😄 So if you refilled until half-full indicated, that could mean anything really - could have been near half, could have been closer to 1/4. Just the way it is. In other hand I found IS250 indicated economy accurate within +/- 1% compared to brim-to-brim, whereas newer cars like IS300h likes to exaggerate MPG and range allot - ~5-10% optimistic. 

[H3XME]

13 hours ago, Linas.P said:

I found IS250 indicated economy accurate within +/- 1% compared to brim-to-brim, whereas newer cars like IS300h likes to exaggerate MPG and range allot - ~5-10% optimistic. 

@Lex_utor

Funnily enough, I was just looking at the official fuel consumption stated on auto trader for IS250 two days ago. Officially, it says 20.9MPG (13.5L/100KM) city and 36.7MPG (7.7L/100KM) motorway. In reality, without trying to achieve the best MPGs, I get ~24MPG (11.7L/100KM) city and ~44MPG (6.4L/100KM) motorway.. I now changed jobs and don't use motorway daily anymore, so my average is ~29MPG (9.7L/100KM), but I think if you get around 300 miles / 500km from a full tank, there is nothing wrong. Of course they were instances where I'd get less than 250 miles to a full tank but that's not a "normal" driving style.. And on the flip side, there were times I could do over 500 miles from a tank just by motorway driving to Scotland and back. (Sadly didn't make it there and back in one tank as the trip is almost 600 miles for me.

[Linas.P]

1 hour ago, H3XME said:

@Lex_utor

Funnily enough, I was just looking at the official fuel consumption stated on auto trader for IS250 two days ago. Officially, it says 20.9MPG (13.5L/100KM) city and 36.7MPG (7.7L/100KM) motorway. In reality, without trying to achieve the best MPGs, I get ~24MPG (11.7L/100KM) city and ~44MPG (6.4L/100KM) motorway.. I now changed jobs and don't use motorway daily anymore, so my average is ~29MPG (9.7L/100KM), but I think if you get around 300 miles / 500km from a full tank, there is nothing wrong. Of course they were instances where I'd get less than 250 miles to a full tank but that's not a "normal" driving style.. And on the flip side, there were times I could do over 500 miles from a tank just by motorway driving to Scotland and back. (Sadly didn't make it there and back in one tank as the trip is almost 600 miles for me.

I noticed that I was probably using US gal for conversion and not British, so my number for L/km are a bit off. But in general same experience 300miles/500km on single tank is about normal, but depends on driving conditions. 

[McShmoopy]

This may be purely a placebo effect, but I recently went down a rabbit hole of E10 additives and I’ve used it a few times and I feel like it’s brought my car a new lease of life. The end result of the additive is fuel which is pretty much like Super unleaded without the extortionate  prices. The car picks up way better it’s smoother and my MPG has had a noticeable increase. City driving improves from 24 to 29mpg and my latest drive to stanstead yielded me a cool 42.1mpg!

[MartinH]

Which additive did you use

[McShmoopy]

8 hours ago, MartinH said:

Which additive did you use

I picked up the multi use one from Halfords for £12 but I was planning to bulk order some from Mannol via eBay as it works out incredibly cheap, however as I was heading to Italy I needed some for a test run. Idea is for every litre of fuel you put in add 1ml of the additive 

[Alfalfa]

2 hours ago, McShmoopy said:

I picked up the multi use one from Halfords for £12 but I was planning to bulk order some from Mannol via eBay as it works out incredibly cheap, however as I was heading to Italy I needed some for a test run. Idea is for every litre of fuel you put in add 1ml of the additive 

I try this on my car.

[Lex_utor]

Thanks for all the replies. I was afraid that could be normal. I almost bought a 350Z as my daily driver instead of the IS250 when I bought mine. One of reasons I didn't was that I thought the IS would be much more economical. 😁

But I'm still suspicious something may be wrong. I will keep a watchful eye. That half a tank, the computer initially said it would last about 225km, if the computer is to be trusted, now it will barely reach 170km. 

Maybe it's the AC. Or my driving style. I like to floor it sometimes, just to hear how it sounds above 4K RPM 😄 

But if that's normal, I would say quite much for a 2.5 liter. Specially being Japanese, I expected better economy. Let's see. I will keep watching it.

LOVE the car regardless. Love driving it and have been loving owning it, apart from the petrol.

Funny how many looks it gets. Surprises me really. I catch guys in new Mercedes, Audis, BMWs and Porsches twisting their head to look at it on the road. I guess it's because you just never seem them around here.  

 

 

 

 

[Lex_utor]

On 7/19/2022 at 4:03 PM, Spock66 said:

The obvious thought would be is there a leak eg loose hose etc, but normally that would be obvious just from a strong petrol smell.

Maybe the fuel tank level sensor was not correctly installed, so your half tank may not actually be a half tank?

First thing I checked. I see no leaks or smells. Sensor, I don't know.

[Lex_utor]

On 7/19/2022 at 4:30 PM, eleveneleven said:

Have you checked your brake calipers recently? 

Calipers are known for sticking which effects the wheel rotation and can end up using more fuel. Check your tyre pressures too. 

It could just be your driving, 500km is about 310 miles. I get about that from a full tank if a majority of my driving is short journeys. 330 miles (530km) seems to be the average for me driving steadily with a mixture of short and long journeys.

I just got a new MOT, so don't think it's the brakes. But I checked yesterday after getting home and the wheels were not hot and put my hands near the callipers and felt no heat. 

About tyre pressure, I have aftermarket 19" wheels. 225/35 front and 255/35 rear.

[Lex_utor]

On 7/19/2022 at 9:11 PM, Linas.P said:

Fill full thank, reset trip and drive until range is 0 and you can even drive another 30-50km easily.

You're a braver man than I. I'm not sure I would risk getting stuck on the road without fuel. :) 

[Linas.P]

2 hours ago, Lex_utor said:

You're a braver man than I. I'm not sure I would risk getting stuck on the road without fuel. 🙂

You know twice I ran out of fuel, one was 200m away from petrol station, maybe even less... 100m, but it was slight uphill and second one was kind of not my fault, I landed in the airport and the petrol station was out of petrol, looked at the trip and realised I still have ~75miles of fuel left and ~70 miles to go. So I drove to the petrol station which was near my home... and that one was out of petrol as well! Then I drove home and car run out of fuel 2m from my parking space. Like literally I started turning into parking space and petrol run out half-way 😄

As well, once I had very scary night in Poland, basically on their paid motorways you can't really drive off, or you have to pay to get off and then back on, so motorway petrol stations knows it and charges premium for petrol. I left Warsaw at like 1AM with 3/4 of tank and my plan was to refuel in petrol station by the border with Germany which I knew is very cheap (like 60% cheaper than motorway ones), because the paid motorway kind of ends there and it is 2km to the side. Anyway that was 474km away. When I was 100km from the destination there was motorway petrol station, but I still had 40km range left + reserve and I skipped it, then like 20km later it said 0 miles left, meaning I have to do 80km on reserve which is kind of scary. But there suppose to be another petrol station after like 40km so I pushed on thinking I will put 10L of "expensive" petrol there to get to cheap station... comes that petrol station and it is closed! F.... so I have 40km left to drive and have no idea how much fuel is left, because I was doing 200-220km/h all along and there are no more petrol stations in between. So last 40km I drove at 80km/h and got there eventually, filled the tank and it only took ~52L, so I still had ~2L left. As well that means car consumed ~8.2L/100k at ~210km/h.

Since then I stopped driving 50 miles into reserve and started doing 10-15 miles maximum and I as well bought 10L jerry can which would be filled with 98 Octane and stashed in the boot for emergencies. BUT actually it is not good for the fuel pump, so I should not recommend it - fuel pump is cooled by petrol and when petrol runs out it could overheat, as well it is better for fuel pump if it is at least 1/4 of the tank left as then it basically floats surrounded in petrol. That said my normal routine would be to drive until it says 0 (meaning ~5-8L left) and drive to nearest petrol station, so maybe 5-10 miles.   

2 hours ago, Lex_utor said:

I just got a new MOT, so don't think it's the brakes. But I checked yesterday after getting home and the wheels were not hot and put my hands near the callipers and felt no heat. 

About tyre pressure, I have aftermarket 19" wheels. 225/35 front and 255/35 rear.

Wheels could be part of the problem, my fuel consumption jumped by ~10% when I went from standard 17" to 18" wheels, so on 19" it may be even more. Really depends on how much they weight, but being 19" I would not expect them to be very light. 

[J Henderson]

7 hours ago, Lex_utor said:

Maybe it's the AC. Or my driving style. I like to floor it sometimes, just to hear how it sounds above 4K RPM 😄 

I'd say the latter is having more of an effect. 😃

A/C will have a small effect, as will bigger wheels. Plus, other factors like tyre efficiency, pressures, wheel alignment status etc.

The biggest factor though, assuming all is well mechanically, is the driver & driving style.

[H3XME]

Like we said before. You cannot get an accurate measurement from half a tank. Fill up all the way to the top until the pump stops. Reset your AVG. Consumption, your trip and drive like you normally would. The range on the screen (100miles left etc changes all the time depending on your AVG consumption. If my tank average was 28 and I fill up all the way, the car can say my range is 280miles with a full tank (because the car assumes I'll be driving like that again and with 28mpg it will only last me ~280miles..), but once I start driving away and go on a motorway, get my AVG to 42, the range suddenly says 400+ miles. Drive with a full tank, until you get the fuel light on. Fill up immediately (if possible) and see how much fuel you used. Have a look at the average MPG for your tank and work out if it matches your trip mileage. 

[H3XME]

On 7/23/2022 at 2:12 PM, Linas.P said:

Wheels could be part of the problem, my fuel consumption jumped by ~10% when I went from standard 17" to 18" wheels, so on 19" it may be even more. Really depends on how much they weight, but being 19" I would not expect them to be very light. 

Depends on what wheel you're going for. Factory wheels are heavy anyway. I went from factory 17x8" alloys with 225/45/R17 & 245/45R17 to lightweight RAYS GramLights 18x9.5" with 225/40R18 on all 4 wheels and my avg MPG got better by 10%.. Driving style is the biggest factor to MPGs. Sometimes I fill up and tell myself "im gonna drive like a grandad for the duration of the tank to see how much I can squeeze out of it" but then I floor it once and MPGs AVG gets so skewed that my results are useless.. It's definitely driving style. Small things like light alloys, narrower (but stickier) tyres, being lowered (aerodynamics) make a difference but if one drives it like they stole it, nothing will help. 

[Linas.P]

Makes sense - you went from heavy 17" with 245 in the rear to light 18" with 225 in the rear, so obviously your fuel consumption should go down. However, going to heavy 19" with 255 your fuel consumption would go up and finding 19" lightweight wheels for reasonable price is very difficult. I know Lexus fits wheels from Aston Martin and there were some light 19" options, at least "light" for factory wheels. I mean sure there are forged 19" wheels for £2000 per corner, but it is much more likely to find really light wheels in 17/18" size, or if going for very cheap - forged 16" used racing wheels. 

I agree that the driving contributes most to overall fuel consumption, but wheels just raises that "bottom line" a bit. For example on 17" I was able to reach that 44MPG on motorway, with 18" it was like 41MPG, because that is it - you just can't get same economy on larger, heavier wheel with wider tyre.

[Mr Vlad]

Out of Interest what is the difference in rolling circumference between a 17" wheel shod with its correct tyre versus a 19" wheel shod with its correct tyre? 

[H3XME]

51 minutes ago, Mr Vlad said:

Out of Interest what is the difference in rolling circumference between a 17" wheel shod with its correct tyre versus a 19" wheel shod with its correct tyre? 

Check this out Vlad https://www.willtheyfit.com/index.php?width=225&aspect=45&diameter=17&wheelwidth=8&offset=45&width2=225&aspect2=35&wheel_size=19&wheel_width=8&offset2=45

[Lex_utor]

On 7/23/2022 at 8:59 PM, J Henderson said:

I'd say the latter is having more of an effect. 😃

A/C will have a small effect, as will bigger wheels. Plus, other factors like tyre efficiency, pressures, wheel alignment status etc.

The biggest factor though, assuming all is well mechanically, is the driver & driving style.

But really, how can you not drive it hard? 😄

You guys don't step on yours?

I'm addicted to the engine sound and it's smoothness. Must be the sound of the multi valve kicking in?

I can't emphasize enough how much I love driving it. I find it the perfect mix between suave comfort and sportiness. Not as floaty as a Jag, not as harsh as a bimmer. Perfect daily. 

 

 

 

 

[Linas.P]

It is perfect daily, although if you like to step on it, then fuel consumption will be what it will be. 

In other hand I never had issue putting fuel in IS250 as much as I had issue putting it into RC200t. In IS250 when you step on it you know you wasting the fuel, but in a good way, like when you shooting money in the sky with fireworks, or throwing the wood plank into bonfire - it is enjoyable sort of waste, because it sounds good and it pulls well. In cars without good sounding engines like RC200t, which sounds like angry hairdryer I just don't feel the same. 

[Lex_utor]

About the wheels, I have been just following the manufacturer's recommended tyre pressures on the door jamb for my 19" as well. Does the IS-F has different recommended tyre pressures for its 19" wheels?

My front tyre kind of looks a bit underinflated. See photos of my tyres thread wear bellow.

 

Front:

 

 

[Lex_utor]

Rear tyre: