How Is The Average Mpg Calculated?

[lawsio]

Hi all, new to the Lexus world this week and have a (possibly very daft question) to do with the economy.

I've just upgraded from a 1.4l petrol Ibiza to an 08 220D, and I seem to be getting the same amount of MPG on my usual run (About 120 mile round trip on Motorway and A roads) now than I did in the Ibiza, roughly 37mph ave (sometimes higher in the Ibiza). However, at coasting the read out on the Ibiza went up to 200mpg, where as the maximum shown on the Lexus is 90mpg. Does this skew the averages or is this just an arbitrary thing from them to stick on the screen?

I've bought the car for comfort rather than MPG,and of course the IS is bigger and heavier so if it is the same then fair enough, I'm just curious. It seems odd that a car apparently designed for eating up motorway miles is as economical as a 1.4l getting ragged to keep up with motorway speeds.

With it being an approved used one (to narrow it down if any of the sales staff read this forum ;)), would things such as the EGR valve and ECU reset which I've seen suggested to boost average MPGs have been carried out? It did have its 5 year service in August as well if not? Or is that a naive assumption?!

If I'm doing about 10,000 miles a year,about 7500 of which are on motorways or NSL A roads, did I make the right call getting the deisel? Having one of those 'buyers remorse' moments and regretting not giving more thought to the 250!

[normski2]

Don't want to depress you but at steady cruising om motorway you would get 37-39 with the 250 Auto.

Having said that my old 220d would do 49 with ease on a run. And still does, my son gets 45 without trying particularly. The mpg on the diesel Lexus seems to vary quite alarmingly.

[normski2]

If you want to reset the ECU then look here

http://www.lexusownersclub.co.uk/forum/tutorials/article/8-resetting-is250-is220d-is200d-engine-ecu/

If you are just a little handy with tools you can check your EGR yourself. It's not that difficult and will only take an hour the first time. You ought to check it only has a light soot dusting and is not close to being clogged. Also clean out the engine port/mouth that is exposed when you lift the EGR body off.

There are many guides to do the EGR. Search this forum or Youtube.

Consider also, the use of BG244 every 8-10,000 miles and AR6400 fuel additive at each fill up. Think 5ml was about 60p.

Take a look here

http://www.powerenhancer.co.uk/

read this too

http://www.oilem.com/content/138-importance-clean-egr.html

forewarned is prepared. Keep on top of it and you will be fine.

[normski2]

This is worth reading too

http://www.oilem.com/content/134-egr-cleaning-egr-cleanersegr-cleaning-egr-cleaners.html

[lawsio]

Cheers! Im not in the least bit handy but I've got a mate who can have a look for me. Does messing with this stuff invalidate the warranty at all?

[normski2]

You could ask that question at your Lexus garage.

In a common sense world they should approve of the fact that you are caring for your car in the appropriate fashion.

However, they can be a tad paranoiac about such things...don't be too surprised if they are! Then just wait until your warranty period has expired. I'm assuming you have a short term warranty with the purchase. But then you may have purchased the 3 year plan.

If this is your process then give it a good run every month or two to give it a bit of a blow out. Getting that engine hot at good revs will promote the action of the fifth injector and so the DPF regeneration process. You need this to be occurring or your DPF will soot up.

[lawsio]

Yes I got a standard 12 month warranty with it. Will check with them before doing anything.

[dazed]

I've just upgraded from a 1.4l petrol Ibiza to an 08 220D, and I seem to be getting the same amount of MPG on my usual run (About 120 mile round trip on Motorway and A roads) now than I did in the Ibiza, roughly 37mph ave (sometimes higher in the Ibiza). However, at coasting the read out on the Ibiza went up to 200mpg, where as the maximum shown on the Lexus is 90mpg. Does this skew the averages or is this just an arbitrary thing from them to stick on the screen?

I suspect it's just a display/calculation limitation. If you throttle off in any modern car the fuel will be cut, giving a theoretical MPG of infinity for a brief period.