I have a Rapid Spaceback 1.0.

 

I noticed an increase in fuel consumption by about 15-20%. Used to go 1000KMs with a tank of gas, but now it only brings me up to the 800KM. This increase in consumption seems to coincide with me changing all 4 tyres. I do not think its the new tyres' rolling resistance since the car seems to coast fine when i take my feet off the pedal. Neither do I think that my brakes are sticking.

 

The increased fuel consumption can be observed when I put my foot on the pedal and accelerate as per normal, but the consumption figures are much poorer than before.

 

Any of you guys have any idea what could be the issue?

Tyres, it happened to my Spaceback back in 2015. Lost 10 mpg but quickly got it back and better as the tyres wore. 

Yeah the 1.0 is really sensitive to any environment changes too - headwinds and gradients especially knock the mpg down, so new tyres( or lower pressures) could make a big difference. 

On 25/01/2020 at 06:39, tanzhihao90 said:

This increase in consumption seems to coincide with me changing all 4 tyres.

Well, start by checking that all 4 tyres actually have the pressure you think they do...

 

Halfords sell a suitable pen type pressure gauge for about £5, so it could pay for itself on one tank.

I cannot say I have experienced such obvious consumption degredation with new tyres. Most of the effects were lighter steering and skittishness until the initial smoothness was worn off.

What tyre did you buy?

Edited 31 January, 20206 yr by Gerrycan

^^^ Exactly this.

 

@tanzhihao90

What tyres came off and what went on and did you compare side by side for size the tyres that were worn and coming off with the new full tread ones going on?

Edited 31 January, 20206 yr by Roottootemblowinootsoot

I had on 215/40R17 Potenzas when I got the car. 
 

My new tyres are 215/45R17 Michelins. 
 

A few shops told me they didn’t carry 215/40 and had to make a separate order for them. Hence the 215/45s. 
 

 

So you fitted taller tyres, more rolling diameter / greater circumference.

Worn smaller tyres vs full size slightly larger tyres.

 

Not a huge difference really but your km's covered are slight showing different. You final gearing is as well, and your speedo. (Not swimming trunks!)

https://tiresize.com/comparison

 

Edited 31 January, 20206 yr by Roottootemblowinootsoot

What he said, and the Michelins may have a different weight and characteristic rolling resistance as well.

Won't the different tyre size make the speedometer reading inaccurate?

 

Or more accurate as it left the factory reading that you are going faster than you actually are.

Regardless, the circumference is different so the Speedo and Odometer (and therefore Mpg) no longer relate to the original figures.

I have recently fitted winter wheels sized for my Yeti to the Octavia, I think they are a whole 2" larger in diameter.

 

I can feel the difference in gearing, the indicated fuel consumption has increaseded and the kms I get per tankfull decreased but I am actually travelling more kms.

 

I think the fuel economy has reduced, the other tyres were Michelin energy savers, the only way I could know is to relibrate the revs/km using VCDS.

On 01/02/2020 at 02:27, tanzhihao90 said:

I had on 215/40R17 Potenzas when I got the car. 
 

My new tyres are 215/45R17 Michelins. 
 

A few shops told me they didn’t carry 215/40 and had to make a separate order for them. Hence the 215/45s. 
 

 

According to the online tyre calculator there would be a 3.6% increase in circumference. Add in a further fudge factor of 0.4% for additional tread on the new tyres for a nice round 4% size variation between old and new.

So for any given indicated speed you would be travelling that much faster (more air resistance) and travelling that much further than the previous tyres.

Accounts for some of the variation you are experiencing though not all.

 

 

On 06/02/2020 at 20:22, Gerrycan said:

According to the online tyre calculator there would be a 3.6% increase in circumference. Add in a further fudge factor of 0.4% for additional tread on the new tyres for a nice round 4% size variation between old and new.

So for any given indicated speed you would be travelling that much faster (more air resistance) and travelling that much further than the previous tyres.

Accounts for some of the variation you are experiencing though not all.

 

 

Actually, I currently only clock 20km/l on a route which I used to achieve 24km/l. 
 

That’s close to a 20% increase in fuel consumption. Which is making me wonder if it could be due to the tyre size alone or if something else is wrong. 

3 minutes ago, tanzhihao90 said:

Actually, I currently only clock 20km/l on a route which I used to achieve 24km/l. 
 

That’s close to a 20% increase in fuel consumption. Which is making me wonder if it could be due to the tyre size alone or if something else is wrong. 

I'm inclined to think there may be something else.

Unfortunately your profile does not say where you are so not easy to guess what other environmental factors may be at play.

 

26 minutes ago, Gerrycan said:

I'm inclined to think there may be something else.

Unfortunately your profile does not say where you are so not easy to guess what other environmental factors may be at play.

 

Haha. I’m in Singapore. Right smack at the equator. So it’s only either hot and dry, or hot and wet. No winterised fuel either. 

5 hours ago, tanzhihao90 said:

Haha. I’m in Singapore. Right smack at the equator. So it’s only either hot and dry, or hot and wet. No winterised fuel either. 

lnteresting.

I would have thought that your aircon in the car would be on all the time and working hard, in which case I am amazed you are even getting your worse consumption.

Edited 15 February, 20206 yr by Gerrycan

@tanzhihao90 @Gerrycan - You've not allowed for any change in tyre mass, which could be significant.

6 hours ago, KenONeill said:

@tanzhihao90 @Gerrycan - You've not allowed for any change in tyre mass, which could be significant.

Good point.

Certainly not something I've experienced or identified but my gut feel would be that since they are both reputable brands the difference would not be much more than a kg difference so per wheel despite the tyre size difference?

When I switched brands between same size 17 inch Dunlop to Michelin there was minimal difference in wheel and tyre weight (bathroom scales) at 21 kg.

The 'spacesaver' spare but normal 16 inch steel rim and Nexen tyre is 16 kg.

 

I have mentioned before the Nexen spare tyre when fitted is the noisiest tyre I have ever encountered and literally screams at you to be taken off. Which is not a bad thing in the circumstances.

 

There is even the possibility that the Michelins fitted on the OP car are not genuine but a cheaper copy.

Edited 17 February, 20206 yr by Gerrycan
Friggin auto spell correction

The Rapid is no longer sold new in Singapore so I looked up an older brochure and the standard 17 inch tyre size for the Rapid is the 215/45/17 you have got on.

So I think that your current (still very good) figures are now more accurate and the older 'better' figures were just lots of inaccuracies for gearings, distances and speeds consolidating into an optimistic figure.

Sorry.

6 hours ago, Gerrycan said:

The Rapid is no longer sold new in Singapore so I looked up an older brochure and the standard 17 inch tyre size for the Rapid is the 215/45/17 you have got on.

So I think that your current (still very good) figures are now more accurate and the older 'better' figures were just lots of inaccuracies for gearings, distances and speeds consolidating into an optimistic figure.

Sorry.

 

Having driven Euro - Rapids for 6 years on 17s the standard size is not what Gerry suggests. It is in fact 215/40R17.

 

However in Singapore you may just be driving the completely different Indian Rapid??

 

 

Edited 18 February, 20206 yr by camelspyyder

1 hour ago, camelspyyder said:

 

Having driven Euro - Rapids for 6 years on 17s the standard size is not what Gerry suggests. It is in fact 215/40R17.

 

However in Singapore you may just be driving the completely different Indian Rapid??

 

 

The brochure I found was from a Singapore web site.

The ground clearance was quoted at 168mm as well.