2010 Auris MPG has suddenly nosedived

[gazzaman28]

Hi all,

I've had my 2010 Auris HSD since 2013 and have been consistently getting decent fuel economy figures. I've got it all tracked on Fuelly.com [click here for my MPG figures] and in the summer I can expect to get no lower than 50MPG (about 54MPG on the dash) and very often upwards of 60MPG (65MPG on the dash) or more. Recently just a day or so apart it got 2 new front tyres fitted and the car had a 10k service, and since then we've had a Fuelly fill-up which said we only did 47MPG and the dash computer is currently struggling to go much over 51MPG. It may only have been a couple of weeks but something is definitely not right. I've been purposely driving it very carefully knowing that it would normally be easily showing 60MPG on the dash computer and it's nowhere near that.

The 2 new tyres are Kumhos, which were a budget choice compared to what we'd had previously, but I wouldn't have expected that to make a huge difference, so I am more suspicious of the service, although it was done by the main dealer who has serviced the car twice a year since new, and we've never had an issue previously.

The odometer is on about 67k as far as I can remember.

Has anyone else had similar experiences and if so what was done to rectify things?

[unclepoo]

With the new tyres being fitted, I`d check the pressures are as you like them....I say this as many run there tyres with a little more psi than the hand-book says. 40psi is  a good place to start.

It might be worth checking the brakes for any binding too...the rears can seize and drag as they do very little work, also check the handbrake for adjustment...I had my Mercedes van in for a service (main dealer), and it came back doing about 10mpg less than before it went in....they`d adjusted the handbrake so they were binding and getting so hot I could not touch the wheel after driving only a short distance....they over filled the oil too.  It went straight back in to be sorted.

[gazzaman28]

Regarding the tyres, they were only at 31psi so I pumped them up to 36psi right away, which is my usual preference. Having said that, reading some of the other threads I might put them up a bit further. In the 50-60 miles driven since then it's not made a big difference (I reset the MPG counter after that and the dash computer is currently showing an average of 51.5MPG).

With the brakes, is there anything I can actually check for myself other than feeling for heat off the disks? I'll check the oil level too.
Would a main dealer try to charge for something like this?

[unclepoo]

If it`s something they did wrong, they should put it right......

As for the brakes...jack each corner up in turn and spin the wheel, in neutral and the handbrake off (so be careful) they should all spin freely, with maybe a very slight drag from the brakes (keep the keys away from the car at this point as the start energizing the braking system).

It would be wise to check the oil level too. Dealers have been known to over fill the oil level, and use the wrong oil grade too..common for them to use a oil too thick. 0-20w is what`s recommended.

[gazzaman28]

17 minutes ago, unclepoo said:

As for the brakes...jack each corner up in turn and spin the wheel, in neutral and the handbrake off (so be careful) they should all spin freely, with maybe a very slight drag from the brakes (keep the keys away from the car at this point as the start energizing the braking system).

Thanks. I thought that having it in neutral guaranteed that only the brake pedal or handbrake actually activated the brakes? What would having the keys nearby do?

[Cyker]

Tyres can make a noticeable difference to MPG, esp. with cars as sensitive as the HSDs.

I deffo second the recommendation about checking what oil they put in too; HSD's *NEED* 0w20 to get the higher mpgs, whereas most garages use 5w30, and we've even caught some Toyota garages putting in 5w30 instead of 0w20 in the past.


 

[johalareewi]

Are the new tyres low rolling resistance ones (aka fuel saver or eco)?

Was the correct oil used on the service (0w20)?

 

[Ancient Nerd]

As you used the same dealer for the service, I doubt very much that oil is the problem, unless a trainee did the work and just used the oil used for everything else.

Tyres are much more likely. I used Kumhos around 10 years ago on one of the first new shape Honda Civic 2.2 diesels. They were certainly quieter than the Michelins they replaced, and I don't remember any great drop in fuel consumption.

However,  on our Gen 2 Prius, I replaced the original C rated Michelin Primacy tyres with Hankooks, which I think are in the same price/quality range as Kumhos. These were a total mistake. Although these were B-rated, they dropped fuel consumption by several mpg. They also didn't last anywhere near as long as the Michelins. And they punctured far more often than any other tyres I've had in many years. They were cheaper to buy, but had a significantly higher cost per mile.

Also, don't forget that manufacturers test their own tyres, so you can't really compare economy ratings across manufacturers, only within one manufacturers range.

[gazzaman28]

I agree that it's unlikely the dealer screwed up but I'll definitely ask the question anyway. I forgot to get our service book stamped so I need to go back and see them anyway.

Tyres for me has been a whole heap of trouble. When the original Michelins wore out I replaced them with Goodyear Efficientgrips which were fine for MPG but I ended up buying about 7 of them over the course of 18 months due to a series of sidewall punctures or sidewall bubbles which couldn't be repaired. Goodyear were not prepared to do anything remotely useful to assist, I was quickly running out of money to throw at it so one of my back tyres was replaced with a part worn Bridgestone (which again didn't affect MPG) just to keep me on the road and things were stable for a while, until I got another sidewall bubble on one side of the front and a sidewall puncture on the other, which meant I just needed 2 tyres quickly to get back on the road. The Kumhos were rated C for fuel (the Goodyears were B) so I didn't expect to have a huge difference in economy from this. This however is a huge and massively noticable difference IMO, but other than swapping both fronts for something better (which means £150 wasted, unless they can be sold) I'm not sure how else to prove what's going on.

[gazzaman28]

Just a thought, would having these 2 Kumho tyres on the back and getting 2 better Michelins on the front make any noticable difference to economy?

[Ancient Nerd]

3 hours ago, gazzaman28 said:

Just a thought, would having these 2 Kumho tyres on the back and getting 2 better Michelins on the front make any noticable difference to economy?

Don't do it. The newest tyres with the best grip should always go on the back. Otherwise you may be dancing in the rain!

Seriously, if you look at what the drop in fuel consumption is actually costing you, it is highly unlikely to be as much as the cost of replacing the tyres. So I think you just have to accept the loss of fuel consumption until they wear out. Then go back to Michelin or Bridgestone next time.

[FROSTYBALLS]

Looking at your fuelly info, you're making a judgement based on one fill up. Wouldn't it be better to get a further couple of fill ups under your belt, and then assessing what the consumption is like.

[gazzaman28]

2 hours ago, Ancient Nerd said:

Don't do it. The newest tyres with the best grip should always go on the back. Otherwise you may be dancing in the rain!

Seriously, if you look at what the drop in fuel consumption is actually costing you, it is highly unlikely to be as much as the cost of replacing the tyres. So I think you just have to accept the loss of fuel consumption until they wear out. Then go back to Michelin or Bridgestone next time.

Quote

 

Yep, I appreciate that, but I'm due to change one of my back tyres in the next month or so as it's below 2mm, the other is at 6mm, so if I buy one decent tyre and move the 6mm to have both of them at the front, I'm not putting myself in any danger. It's certainly an option but I don't honestly know if having less economical tyres at the back rather than the front will make much difference to fuel costs.

As far as the drop in consumption goes, assuming I can get 15k out of the tyres (which is I think a bit conservative, it's more likely to be 20k) then I work out the following:

At £1.099/litre
48MPG: 15k x 10.4p/mile = £1560
54MPG: 15k x 0.92p/mile = £1380
60MPG: 15k x 0.83p/mile = £1245

So i'm looking at spending between £180 and £315 more on fuel over the life of the tyres, and that's if they are the cause of the current woes.

[Cyker]

@Ancient - Is that still considered true for FWD cars?

I always figured you'd want the grip on the front in an FWD car, since losing the rear end is much easier to get out of in a FWD (i.e just steer where you want to go and accelerate out of it), whereas losing the front is basically impossible to recover from (You have to hope the car slows enough to regain grip before you plough into a ditch or something)

 

[gazzaman28]

2 hours ago, FROSTYBALLS said:

Looking at your fuelly info, you're making a judgement based on one fill up. Wouldn't it be better to get a further couple of fill ups under your belt, and then assessing what the consumption is like.

I'm only 100 miles off my 2nd fill up and I'm currently averaging a shade over 50MPG on the dash computer (so about 47MPG on Fuelly). That's somewhere above 750 miles so far at around 5MPG down on my overall MPG and more like 8-9MPG down on my MPG at this time of year. I think I'm justified in saying "I have a bad feeling about this..."

[Cyker]

Has it been quite cold where you are recently?

 

[gazzaman28]

2 minutes ago, Cyker said:

@Ancient - Is that still considered true for FWD cars?

I always figured you'd want the grip on the front in an FWD car, since losing the rear end is much easier to get out of in a FWD (i.e just steer where you want to go and accelerate out of it), whereas losing the front is basically impossible to recover from (You have to hope the car slows enough to regain grip before you plough into a ditch or something)

I actually missed that @Ancient had said rear...I'm assuming that was a typo and he meant front. You would generally want your best tyres on the driving wheels, I'm not aware of any RWD hybrids.

[gazzaman28]

30 minutes ago, Cyker said:

Has it been quite cold where you are recently?

Nope, it's averaging about 18C, typical Scottish summer, possibly even slightly above average. I can normally expect really good economy between May and September.

[Cyker]

Ahh, just a thought. I always picture Scotland in perpetual blizzards 
 

[FROSTYBALLS]

Where one is renewing just two tyres, for a number of years, industry best practice has been to fit new tyres onto the rear axle, and to move the part worn rear tyres to the front - this is regardless of whether a car is either front or rear wheel drive.

[johalareewi]

Interesting. I have had FWD drive cars for many years and my experience of the tyre fitting industry practice has been to put the new tyres on the front and move the worn tyres to the rear.

[johalareewi]

19 hours ago, gazzaman28 said:

Tyres for me has been a whole heap of trouble. When the original Michelins wore out I replaced them with Goodyear Efficientgrips which were fine for MPG but I ended up buying about 7 of them over the course of 18 months due to a series of sidewall punctures or sidewall bubbles which couldn't be repaired.

After years of Michelins I got Goodyear EfficientGrips.  Yes they are quieter and cost a bit less but they haven't lasted as long.  I will be lucky to get 20,000 miles out of them.  The Michelins can easily do twice that.

[FROSTYBALLS]

Back in 1998, when I needed to replace two tyres on my 1996 Corolla, Costco rigidly followed Michelin's stance on replacing new tyres, and would only fit new tyres to the rear, rotating the used tyres to the front (at their cost). They would turn away business, rather than go against Michelin's advice.

http://www.michelin.co.uk/tyres/learn-share/care-guide/ten-tyre-care-tips  (see point 6)

http://kumhotyre.co.uk/kumho-news/should-you-fit-new-tyres-to-the-front-or-rear/

http://www.theaa.com/motoring_advice/safety/car-tyres.html

[kithmo]

Although a valid argument, better tyres to the rear is only really necessary when cornering in the wet and pushing the car to the limits, not something most people do everyday.  I personally would argue that if most of the braking, all of the steering and on a FWD vehicle all of the driving, is done by the front wheels, then that's where I want my grip and that's where I would put my best tyres. On the other hand if I wanted to wear the tyres out quicker, to replace them to even up the tyre wear on the whole car then I may put nearly worn out tyres on the front as they will wear faster there. BTW I always replace tyres when the tread is down to 3mm so there's usually still plenty of grip in them before that. 

[gazzaman28]

In terms of economy (rather than handling), would having 2 energy saving good quality tyres at the front and 2 cheaper tyres at the back be better for a FWD hybrid or would it not make much difference because the cheaper tyres will increase drag wherever they sit on the car?