car economy question
 

lately my car has been thirsty and today i think its been to thirsty

today I've been to Exeter and back (about 220 miles). The 1st 20miles of it were motorway and dual carriageway and my fuel dropped a fair bit so worked out the MPG in my head and it had done roughly between 22-25 MPG, that was sat at 70 with cruise control most of the way..........not odd you may think but its a 1.4 :-k

the rest of the journey it was fine and did what it usually does

i can't work out why its drinking so much, it has no performance mods, serviced regularly, not leaking, not playing up in anyway and I'm driving with a feather boot on :confused:............. its does need a new back box though as the current one is rusted and all loose inside, but no wholes and still passed the MOT

could that cause low MPG? or what else could be up? :-k

Re: car economy question
 

tyre pressure?

Re: car economy question
 

You not mentioned tyre pressures. One of my daughters things used to be to phone and moan her car using lots of fuel and so must be broken... I'd say have you checked the tyre pressures?.... Silence.... :D

Hers was a 1.4 and would do low 20s when her tyres were flat.

Re: car economy question
 

were you parked on a slope at the start of the journey, my car has a delay on the sensor to equaite for bumps etc so it may have started atrificially high.

Also on a 200 mile trip in a volvo 2.0 Turbo diesel I did a test - the cruise control at 75 averaged 45 mpg - I averaged . . . . . . 60!! and according to the computer the average speed was actually higher!

Re: car economy question
 

aha tyre pressure could be it :p, i had a feeling my compressor gauge was out a few weeks back

Re: car economy question
 

Tyre pressures and I would check the air filter - see how dirty it is - that wont help.

Re: car economy question
 

Aye, who did the servicing, you or another (in)competent mechanic?

If a garage did it, then don't rely on them adjusting any fuel air/mix for best fuel economy. They'll just change fluids, filters and grease bits if you're lucky.

If you did it, then change the air filter and get the engine tuned. I had one of those mobile tuning guys come round and tune up my Cav. Needs doing again, although it hasn't failed on the emmissions at MOT since I had it tuned, and that was years ago.

Re: car economy question
 

i did alot of work on it about 300 miles ago done by me, oil, filters, plugs, belts, coolant, water pump and brakes but it was like it before. i did have a ECU fault a few months back but was plugged in and turned out to be a loose connection on it

Re: car economy question
 

[QUOTE=maviczap;2028123]Aye, who did the servicing, you or another (in)competent mechanic?QUOTE]

I'm not suggesting you are an incompetent mechanic by the way :p

Having taken various cars to dealerships and hearing a work colleagues tales about when he worked for a Ford dealer, I wouldn't take my car to a main dealership.

I prefer my local independant these days. Mostly on price, but at least they don't try and rob you blind for work you don't need doing, or charge you the earth for parts for the work you don't need doing.

Step forward Vauxhall main dealers :reaper:

Re: car economy question
 

i've only ever taken it to a dealer with a computer fault, but even then i watched them :lol:.......... hate garages

Re: car economy question
 

Get the man round with his diagnostic tools then :smt024

Re: car economy question
 

Exhaust could be playing a big part in it. Get that sorted then take it from there.

Re: car economy question
 

put it in neutral and roll on down hill sections of road :)

Re: car economy question
 

Surprising fact f/i--A car uses more fuel rolling down hill in neutral with the engine running than in a high gear with the throttle closed. Basic explanation-- throttle close in gear delivers no fuel to the engine as the vehicle is using the gearing to control the speed and turn over the engine--Whilst in neutral the engine has to be kept running so the ECU delivers a fixed amount of fuel to maintain engine speed.:D
As you have said you have been having trouble with the ECU and the problem was at the beginning of your journey it is possibly a heat sensing problem delivering to much fuel. This could be a simple thermostat[water] problem or one or more of the engine ECU sensors
You have said it is a 1.4 but what car and model? This would help as certain types of vehicles have repetitive fault traits:smt022

Re: car economy question
 

astra/G mk4 1.4ls

Re: car economy question
 

Bearing in mind its early in the journey, automatic choke?

Re: car economy question
 

the exhaust could be playing a big part...

IF, the baffles are collapsing the gasses will not be flowing properly, the lamda sensort (assuming it has one) wont be reading correctly thus messing up fuel air ratios.

I wouldn't say its a long shot, but you haven't told us what you normally get to the gallon, if its 30, then tyres or exhaust if you used to get 45 then its something worse i reckon.

when my Renaults cat collapsed my mpg dropped from 32 to 14mpg in two days.

Re: car economy question
 

Ah the clutch and roll game - me and the missus try to out-do each other in clutch and roll distances! I usually win as my car is heavier!

Re: car economy question
 

Ive never known a fuel guage to be anywhere near accurate enough to measure fuel consumption.The only way is to brim the tank,zero the trip, and drive for a couple of hundred miles and brim it again.Then do the arithmatic.

Re: car economy question
 

Or use the on-board computer as thats a constant algorithm

Re: car economy question
 

Do they work?Or are they just another gimmick?I dont run a modern car,but on the older ones I previously ran the dashboard fuel consumption figures were complete fiction.

Re: car economy question
 

volvo's do - I coughed into a petrol station with my 'miles left gauge' saying 0.2!!

I also did the fill to brim, did 200 miles and filled again and got the same result mpg calculations wise.

Re: car economy question
 

A lot of old mpg gauges just read engine vacuum. Boot it and watch gauge dissappear off to the end saying "sluurrrrrrp" lol

Re: car economy question
 

My mate nearly got screwed for new discs and pads from the local Vauxhall dealership last week. He only knew he was getting stiffed as 1 month previously, it had had a full check up (including thorough brake checks) by an independent company, and they had given it the all clear.

The car only does 20 miles a week!!!

F**king Vauxhall dealers!

Re: car economy question
 

The new Transit vans are quite accurate, until you get down to the last 30 miles. That disappears in 10 or less miles!

Re: car economy question
 

Yes, had this happen to me twice. Once for a new clutch and the 2nd time was for rear master cyclinders. Two different garages too. Tried to stiff me for new front pads when they had loads left on them.

Didn't get stiffed for the cambelt change, as I'd found an independant. Vauxhall price £200+ , independant £40

Now I'm more car mechanically minded, I won't get stiffed again if I can help it.