Hi all

Basically just wondering if you could help me on two things

Got my tyres changed before the weekend and fuel consumption has been effected. Was previously running two Sunny SN3800s(it's a second hand vRS, I wouldn't put that ****e on) on the front with two Conentinal SportContact2's on the rear. I replaced all four corners with Goodyear Eagle F1 GS-D3s. Over the weekend fuel consumption was definitely worse than usual, struggling to hit 50mpg on a 100mile 50mph run. To cut a long story short, this morning I got the car serviced by a main dealer and just did my usual drive home and only averaged 43mpg, whereas I can usually average over 57mpg. My question is can tyres have that much of an effect on fuel consumption?

Also since I got my car back after the service, there is a whining sound around 2k rpm. I have had a PD160 intake fitted previously but never noticed the sound before. However one point to note is that the guy at the garage told me that the air filter was completely blocked so perhaps the engine wasn't getting enough air that it was supposed to and hence the reason why I am only noticing this sound now.

Your help is much appreciated.

are the tyre pressures set right ?

new tyres can/do make a difference to the fuel consumption

are the tyre pressures set right ?

new tyres can/do make a difference to the fuel consumption

Yes they are all correct....I knew they could make a difference but not such a difference!

if they've fitted a new air filter and possibly had it on the diagnostic tester they may have reset something in the engine management , the consumption may get better after a couple of drives

i know we can (Ford) reset the KAM (keep alive memory) and it takes the engine management a bit to relearn all the sensor values etc

If the air filter was badly clogged, I would expect you to see a dramatic increase in MPG not a decrease.

I change my air filter every 10k miles, and usually see the MPG figure go up by +4 MPG approx, even though the filter looks fairly clean.

Sounds like it was reset at service, as said, and will probably climb the more you drive. Also the Goodyears or a softer tyre compound than the Continentals/ditchfinders, so will grip more - more drag - less mpg.

Sounds like it was reset at service, as said, and will probably climb the more you drive. Also the Goodyears or a softer tyre compound than the Continentals/ditchfinders, so will grip more - more drag - less mpg.

lol... "ditchfinders" ..... :rofl:

lol... "ditchfinders" ..... :rofl:

agreed , classic Shifty :rofl:

Sounds like it was reset at service, as said, and will probably climb the more you drive. Also the Goodyears or a softer tyre compound than the Continentals/ditchfinders, so will grip more - more drag - less mpg.

If they were to do a reset would that mean disconnecting the battery? As I don't think that has happened seeing as the odometer/trip computer has not been reset...

lol @ "ditchfinders"

IMO the Goodyears are partly responsible for the MPG woes. They're not all that soft but the sidewalls are quite soft for performance tyres.

The ECU provides fuel based on the amount of air consumed. A dirty air ilter will have less of an effect at lower revs but as the mass flow requirements of the engine rise (revs and boost), it'll strangle the engine. You'll have a slower, less responsive car, but possibly a more economical one.

BTW: If anyone wants ditch finders, try Conti ECO contacts compared to Sport contacts. Not too good in the dry but lethal in the wet. Especially if fitted by the "blah blah - new tyres to the rear" regime,

J.

quick response to vindaloo,

iv just fit a pd160 pipe and have noticed a drop in fuel efficiency, why is this? is this because more air is getting in?

Has any1 else had this problem?

Also the car is making a jubbering noise well putting my foot down in low gears

I think the general principle is that to make more power you need more air AND more fuel , so if this is correct , and you can feel your car is 'perkier' than without the intake , then you will be using a tad more juice.