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Low MPG and white smoke/steam from exhaust.


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Hey guys.  

Sorry for yet another IS250 thread. Just looking for some typical common maintenance advice really. (Will be updating my previous threads with pics soon. Had some bad news and spent some time away so it's been on the side for now)  

Basicly i've just done a nice 200 mile round trip and noticed my MPG really struggled to get about 30. At the end of the 200 miles i only just cracked 30.4mpg and that was a steady pace 70mph in 6th gear for the entire time never mashing the throttle. I drove like a granddad trying to acheive the best possible MPG on a motorway run to compare it to my town runs.  

For reference taking the kids to school and dropping the wife at work netted me 18mpg while 200 miles of calm smooth moterway netted me 30.4 with a struggle. Is this normal? I'm sure the IS250 should be a tad higher on the motorway? If not what area's of the engine should i start with cleaning/changing?  

Next is there's plenty of steam coming from the exhaust. White smoke yet i'm not burning any coolant or oil. This tends to come and go mainly in traffic or slow moving. Once above 30mph i don't notice it at all. Could this be a blocked valve? Excess fuel? Left over water in the exhaust from rain/pressure wash? How long would water really last in the exhaust to be honest after a 200mile round trip? Should be all gone right?  

I've already got spark plugs, air filter, oil filter and 10L of nice fresh 5w-30, cabin filter and new sump plug o ring. Along with a nice big bottle of brake/carb cleaner. Should i get myself a PCV valve on order or can i give that a blast with brake cleaner and a soft brush? Could cleaning the throttle valve help reduce white smoke? I'm not losing any fluids so unsure what this steam could honestly be?  

The car is a 56 plate IS250 manual with 111056 miles and the last service from Lexus according to the paperwork was in 2018 in Lexus Wembley.  

I'm tempted to book the car in for a free vehicle health check at my local Lexus dealership (If they still do that? I see it printed in the owners manual) also once i get the V5 will see if the timing chain was changed in the last service or if i should book it in for the full 100 just to be safe as possible.  

Thoughts?

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I've just found This link.  

So it seems like it's normal for this car. I'll get a new valve ordered anyway and give the throttle valve a good clean while doing everything else. While the car is on it's stands draining the oil i have an anti roll bar that needs a good exfoliation and coat of paint which looks like a real pain to reach but this is what kids are for right?  

Then i get to pull out my new toy... Sand blaster 6000 🙂  I'm going to blast away any and all corrosion under the body and apply an insanely excessive amount of underseal. Hope the wife didn't need the cardboard boxes upstairs... They're going to be taped to all wires and pipe work before blasting. I love detailing my cars inside and out along with making sure everything looks brand spanking new. It gives me something to do as a full time father of 4. Also it gets me out of the house for a few hours 🙂  

If there's anything else you guys can tempt me in doing i'll take a look at the same time.

 

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  • 2 weeks later...

I get the same with the white smoke and with the thread you found, think it's normal.

On the mpg - which figure are you watching? average mpg or tank MPG? I'd use the tank MPG and reset it on the motorway (long press on Mode button on the steering wheel I think). It resets itself after each refuelling so if you did many mile around town at 18mpg then when averaged with the 40ish MPG on the motorway it probably settled at 30? 

mine is a 55 plate and I get around 25mpg around town and a combined 30-32 with some motorway/country lanes driving to work and back. 

spark plugs and oil I think will help with MPG - also check your tire pressure. Cleaning the MAF sensor is a good idea too as seen some people doing it and it helped with MPG and the car felt more responsive.

haven't cleaned my PCV & throttle body yet but know a friend that has. Apparently the PCV shouldn't be as bad as you see on US forums because the fuel quality is better in the UK. 

& good luck with the sand blasting! never seen anyone doing this to their car but sounds like a good idea!

 

Where are you based in WM? I'm in Coventry/Nuneaton

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On 2/11/2022 at 10:29 AM, zoricib said:

I get the same with the white smoke and with the thread you found, think it's normal.

On the mpg - which figure are you watching? average mpg or tank MPG? I'd use the tank MPG and reset it on the motorway (long press on Mode button on the steering wheel I think). It resets itself after each refuelling so if you did many mile around town at 18mpg then when averaged with the 40ish MPG on the motorway it probably settled at 30? 

mine is a 55 plate and I get around 25mpg around town and a combined 30-32 with some motorway/country lanes driving to work and back. 

spark plugs and oil I think will help with MPG - also check your tire pressure. Cleaning the MAF sensor is a good idea too as seen some people doing it and it helped with MPG and the car felt more responsive.

haven't cleaned my PCV & throttle body yet but know a friend that has. Apparently the PCV shouldn't be as bad as you see on US forums because the fuel quality is better in the UK. 

& good luck with the sand blasting! never seen anyone doing this to their car but sounds like a good idea!

 

Where are you based in WM? I'm in Coventry/Nuneaton

Hey. Sorry for the late raply.
I've changed the oil, bled the brakes, air filter is good and clean. I've also cleaned the throttle body with a bit of brake cleaner and a brush. Nice and clean now. The mesh behind it was pretty black and nasty.
My tire pressures were a little low so pumped those up a bit more.  

Around town i now average 22mpg but i'm pretty heavy on the throttle, slowly learning to be gentle along with using more gears. Just pottering around town in 5th gear at 30mph seems to help with my MPG. I've not had a chance to get out and do the other work due to rain, work, kids etc... I'm about to fill up with E5 to see if that makes a significant difference. If i can manage 28mpg the £6 price difference works out in my favour.

I've been following the average MPG not the tank but the tank seems to be the same. Currently have mine set to outside temperature as i find myself desperately trying to increase the numbers rather than just enjoying the drive. It's not bad tho. Taking the kids to school and back with the odd shopping trip uses 1/4 tank a week so it's not bank breaking.

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