Fuel Consumption Problems

[tarantula_123]

Hi,

My 2002 Toyota Yaris 1.0 has recently decline in fuel consumption, and I'm wondering if anyone knows what the problem may be.

I topped up £10 recently at the cost of 128.9pl and done a test to see how far it went without flashing. I lost the slip i noted the figures down on, but im pretty sure it dropped down to flashing on either 61.9 or 69.1 miles.

Most of my driving is going to university roughly 3-4 times a week, which entails a motorway journey. The rest is just usually for odd trips to the supermarket. Nevertheless, for £10, it should realistically be getting more than this.

The car is regularly serviced and looked after, so there is no problem there. The tyres and brakes are all new on it, and it has not long had a new clutch.

Hope someone can point me in the right direction.

Thanks,

tarantula_123

[Cyker]

What are you expecting to get? Is it quite a major drop?

It may be weather related, but it's been winter for a while now so I'd have expected any mpg loss to have started months ago.

If you only noticed it after the service and tyre changes, may be they've used a thicker oil (Or does oil need some heat cycles to loosen up??). Another thing it might be; When I got new tyres from Toyota, they only inflated them to 32/30psi and that did have a noticeable effect on my mpg (I normally run 38/35!) so the pressures may be worth checking too.

[tarantula_123]

Hi Cyker,

Im expecting the desired 50mpg. 40 or below for a 1.0 litre is not right.

I know i said 'recently', but it has been happening a while before winter. I can't really recall how long, but more or less within a year, as my first year or two at university seen me gain roughly 100+ miles out of £10 worth of fuel. Yes, the prices were slightly cheaper then, but not so much as to give me such low fuel consumption.

Regarding the oil - I use Castrol Magnatec. I always buy my own parts for services so i know what im getting.

Regarding the tyres - 38/35 seems excessive? I know its recommended 33 front 30 back, but i will check up on that.

Thanks,

tarantula_123

[4raver]

69.1 miles is equal to 50 to the gallon and not too bad in winter.

[Mooly]

The only way to get an MPG reading is to brim the tank each time so you know exactly how much fuel has been used. Relying on the gauge and low fuel warning light isn't nearly accurate enough.

[Konrad C]

I have a dislike of the £10 of petrol culture. There are too many variables.

Cyker has covered the weather and Mooly has said about brimming the tank and zero the trip counter then repeat.

Tyre pressures really do make the difference.

The petrol quality may have changed, or the station you are using may not giving the correct amount of fuel.

Driving conditions like traffic, route taken, change of driving style, may influence your consumption. Weight is another influence ( I am not saying you have put on weight).

Maybe there is something wrong with your car like dragging brakes! Has the EML illuminated.

Unless you get data logging equipment to monitor your car and usage, you will have to follows Mooly's advice.

[Cyker]

This is a bit out there and probably doesn't apply, but one issue might be that running a partly filled-tank means there is air and you can get increasing amounts of condensation inside the fuel tank.

With pure petrol I don't think this is a huge issue, but it is with diesel and ethanol blends.

With ethanol blends, the ethanol soaks up this water and it ends up going into the cylinder with the rest of the fuel which can corrode the injectors and cause other associated problems of water getting where it shouldn't..

With diesel, the water forms a layer on to where algae and stuff start to grow and form a layer of crap that can clog the fuel filter if the tank is run very low.

The cure is to always brim the tank, but TBH this is all theoretical - I think most petrol here is either pure or 5% ethanol blend at most, and unless the car is sitting for ages with a partly-filled tank there shouldn't be enough condensation to cause a problem anyway!

Still, see how things get on when the weather starts to warm up (I note this is a slightly ironic statement to make since, apparently, it's going to snow soon... )

Edit: Bad forum! Stop eating all my line feeds! Raist has a thread full of jokes that are far tastier! :D

[Raistlin]

That's it look on the bright side... Brrrr