Low Fuel Economy

[seamus1]

Hi All

I have been driving an Auris Excel Hybrid for the last year, have clocked up around 20k miles and had the main service last week.

On the plus side, my front tyres lasted the full 20k and have now had the fronts replaced too. Kwik Fit put Continentals on and not the same make as when the car was supplied.

I have noticed a drop in mpg, before I was getting around 60-70mpg around town and 53mpg on the motorway. Currently I am struggling to get past 43mpg with the same driving style.

Has anybody else noticed this after changing tyres? Or after the main service?

Thanks

[RunningInPleasePass]

Check you have had the correct oil used OW/20

See: http://www.toyotaownersclub.com/forums/topic/125657-that-engine-oil-again/

[PeteB]

Also that the oil is not over filled - dealers frequently do this and it seems to harm the mpg.

Are the Contis Low Rolling Resistance?

[seamus1]

Thanks for the replies.

I will need to ask the dealer about the oil tomorrow.

I think it could be the tyres

The car was supplied with Dunlop SP Sport Fastresponse. EU fuel rating B-E

The 2 front tyres are now ContiSportContacts, EU Fuel rating E/F.

They also replaced a rear tyre with a Dunlop Sport Max, EU Fuel rating C-F

What do you think?

Thanks

[FROSTYBALLS]

As the original tyres were Dunlop SP Sport Fast Response, I presume you have 17 inch wheels. Continental Sportcontact 5's are also OE tyres for the Auris with 17 inch wheels. None of the OE tyres for the 17 inch wheels are Eco tyres.

[johalareewi]

After a service, check they used the correct oil 0w20.

Also check the tyre pressures.

It is not unknown for garages (even Toyota ones) to leave them under inflated.

When changing tyres make sure new tyres are low rolling resistance (or similar fuel rating to the old tyres).

[Grumpy Cabbie]

My money is on both the tyres and the oil.

Low Rolling Resistance tyres make a significant difference to fuel economy, especially at A road or motorway speeds. 5% or 10% difference on a car getting 60 or 70 mpg makes a big difference. 5% or 10% on 30 mpg is barely noticeable.

But the oil also makes a big difference. The 1.8 hybrid must use 0w20 oil to get the best economy but many lease companies insist on using the cheaper 5w30. Now it won't damage the engine using the thicker oil but it really does affect economy at the top end.

Years ago when the gen3 Prius was brand new my dealer put 5w30 in by mistake. My economy collapsed from getting 60-75 mpg on a run, to about 50-59 mpg. Doesn't sound much but it was almost impossible to get the car to average 59 mpg on a trip where it would get 75 mpg previously, and 50 mpg when I'd get 60 mpg before.

The Toyota hybrid is highly tuned for economy in the same way a Ferrari is tuned for performance. All those little 1% gains here, 0.5% gains there, all add up to make high and easily obtainable mpg figures. Once that balance is upset by using E rated tyres or thicker oil, you find the car will perform similar economy to a normal car.

Imagine said Ferrari having WingWoo tyres stuck on it to save a few quid, and then bunging on a cheap eBay special exhaust. You know it wouldn't corner or go as well as it could if correct parts were used. Extreme example but you get what I'm saying.

[kithmo]

Nothing wrong with Wingwoo Ditchfinders I had a set fitted to my Bugatti Veyron.

new tyres will likely have a greater rolling resistance than used ones, they should get better as they bed in. I'd check the tyre pressures as well, pump 'em up a bit more than recommended by about 3-5 psi.

[Grumpy Cabbie]

lol I do like that combined effort there.

A set of Wingwoo Ditchfinders. lol.

[Berisford]

I won't dispute that the correct oil and eco tyres both contribute but, I suspect our OP will have to look elsewhere to get a 50% increase in his new mpg figures to get back to where he was before the service............

[JSHarris]

Another vote for the wrong oil. On my first Gen 2 Prius the dealer used the wrong oil in three out of five services. Each time I could tell within a week because of the hefty increase in fuel consumption, once the wrong oil even triggered an oil warning light, IIRC. Each time I got the dealer to change the oil for the correct stuff and got into the habit of handing them a copy of the Toyota TSB warning about using the wrong oil in the Prius. Even when handed the TSB they STILL put the wrong oil in!

Also, as pointed out above, dealers used to frequently over-fill the oil, and this also has an effect on fuel consumption. Well worth checking. I got into the habit of flipping the bonnet and checking before I drove the car out of the dealer after a service, and if it was the usual 1/2" above the "max" mark got them to drain some oil out.

I remember on one of the Prius forums back around 2005/2006 this was a very, very common problem, with a high proportion of owners suffering poor fuel consumption because dealers were over-filling and using the wrong grade of oil.

The tyres may not make a massive difference, as even the original fit 17" tyres are already poor when compared with the 15" ones (in fuel economy terms), but added to the wrong oil, or too much of it, they may well be compounding the problem. I never understood why they fitted these low profile tyres to the Gen 3 T4 and TSpirit Prius and am grateful that my Plug In has gone back to the 15" rims that my old Gen " Prius had (not only better economy, but a better ride, too).

[Grumpy Cabbie]

I won't dispute that the correct oil and eco tyres both contribute but, I suspect our OP will have to look elsewhere to get a 50% increase in his new mpg figures to get back to where he was before the service............

In the hybrid they really do make a difference. The thin 0w20 oil really does make a difference to the hybrid engine which is switching on and off all the time, even at 50 mph or over. I have 12 months and 34,000 miles of stats on fuelly and you can see a definite dip in my mpg averages during the period where only the wrong (5w30) oil was used, reflecting the experience of the OP.

The is where the problems arise. I'm sure the mechanic in the service bay just assumes oil is oil and bungs whatever is nearest to him. Normally there is no problem, but in the hybrids it is. It has been reported numerous times on this forum and at significant length on the US Priuschat forum too.

There are 3 or 4 things on a Toyota hybrid that significantly affect mpgs;

1, Wrong oil (should be 0w20 in gen3, all Auris HSD and all Yaris HSD)

2, Low Rolling Resistance Tyres

3, Correct tyre pressures (which can appear high and are often erroneously lowered to 30 psi by some dealers)

4, Faulty 12v Battery causing the car to continuously try and charge it affecting economy. There is no alternator.

The top 2 are the main ones.

[kithmo]

Another vote for the wrong oil. On my first Gen 2 Prius the dealer used the wrong oil in three out of five services. Each time I could tell within a week because of the hefty increase in fuel consumption, once the wrong oil even triggered an oil warning light, IIRC. Each time I got the dealer to change the oil for the correct stuff and got into the habit of handing them a copy of the Toyota TSB warning about using the wrong oil in the Prius. Even when handed the TSB they STILL put the wrong oil in!

Also, as pointed out above, dealers used to frequently over-fill the oil, and this also has an effect on fuel consumption. Well worth checking. I got into the habit of flipping the bonnet and checking before I drove the car out of the dealer after a service, and if it was the usual 1/2" above the "max" mark got them to drain some oil out.

I remember on one of the Prius forums back around 2005/2006 this was a very, very common problem, with a high proportion of owners suffering poor fuel consumption because dealers were over-filling and using the wrong grade of oil.

The tyres may not make a massive difference, as even the original fit 17" tyres are already poor when compared with the 15" ones (in fuel economy terms), but added to the wrong oil, or too much of it, they may well be compounding the problem. I never understood why they fitted these low profile tyres to the Gen 3 T4 and TSpirit Prius and am grateful that my Plug In has gone back to the 15" rims that my old Gen " Prius had (not only better economy, but a better ride, too).

The 17" rims are purely for looks, some prefer them. I can take them or leave them, it just happens that the T-spirit versions of the Gen3 and Prius+ I have owned had them anyway.

I could never understand why they made them so wide though, 7" IIRC, it's not a performance car, narrower wheels would have had cheaper tyres as well.

[barrycoll]

This thread seems to have lost touch with Low MPG, but............

Of course you are right Keith, the 17" are all for looks. And width is probably for looks too

Way back in 1960's eg (another life time), I ran a 3.8 Jaguar E type. 15" wire wheels and 185 section Dunlop Roadspeeds which were the ants pants at that time.....but when looking at a 1965 E Type now, the wheels looks weedy and the size spindly.

And somehow, the 15" on the Prius look similar, as the bulk of the car seems to overpower them, although maybe that is the design of the wheels, as the new Golfs on small wheels dont look as limp wristed.

But I may as well nail my colours to the mast here, and say that even though my T Spirit was specced for a set of frumpy 15", when I saw it on the forecourt, whiter than white, and all tarted up in a set of 17" high heels, my heart leapt, and it was love at first sight.

A low three quarter front view, where the windscreen and bonnet line become one, and the very pretty 5 spoke 17" alloys are on full display, shows just how photogenic the Prius still is

[Nina]

I'm not an expert on the question about fuel economy, but I can confirm that after the oil change I get better results. Last time I checked, it was 46 mpg.

[Grumpy Cabbie]

46 mpg? You sure? That sounds like you have a problem or at least something isn't optimum. I have the biggest, baddest lead foot going and I'd struggle to get 46 out of my worn out gen3 Prius. Well, unless you do lots of 1 mile journeys. If I do nothing but trips of a mile each way to the shop I'll get about 46 mpg, but anything longer where the car will warm up I'll get a minimum of 50 mpg.

Reset your trip and see what happens.

[Chris Dance]

Small local runs return in the upper forty or low 50 MPG for me but a long run is usually over 60 MPG. I always reset the trip after refuel. Our car has only done 200 miles so I am expecting fuel consumption to improve as the engine gets more run in.

[barrycoll]

We had a recent minicab Prius to the airport. The driver didn't own the car, and either accelerated hard, or braked hard...not much in between.

I noticed that the Overall MPG figure on the dash was 47.7, and the car had done 40k miles, possibly with the Trip never reset.....that must have been the case, as after 20 miles it hadn't moved either up or down, and must have been over the total mileage

[Grumpy Cabbie]

It sounds about right if he drives like that. I averaged 49.7 mpg over 12 months. Remember that that is in 10 hour shifts 6 days a week. It's easy for one to say you can get 65 mpg in town, but there's no way over 10 hours x6 x 52. But even if that driver was getting 47 mpg, it's better than the 35 mpg in a manual diesel Mondeo, 29 mpg in a petrol, and much less in an automatic as a taxi.

But yes, if a taxi is getting 47 mpg driving like a fruit and the OP is getting 46 mpg driving gently? Hmmm, something's wrong somewhere.

[seamus1]

Thanks very much for all your advice and replies.

I took the car to Toyota, they advised that I had 3 different brands of tyre on my car which isn't good for a hybrid, they definitely used the correct oil and checked the car over and found no fault.

I was still getting low MPG, I drove to London and back to Bristol on Sunday, 39mpg was the best I could get.

The car is a lease car, I had already had a discussion with the Fleet Vehicle Service Manager so decided to pay him a visit.

Luckily at the time, an experienced ATS fitter was with him and checked over my car. They then took my car for a drive, felt that it seemed to have a choppy ride and high road noise from the rear.

The Continentals got swapped to the back. The Dunlop Sportmax was moved to the front and a new Dunlop Sportmax was added. I now have the same brand of tyre across each axle.

The tyres were filled with Nitrogen, not air, balancing was done and tracking was checked, the tracking was spot on but the car still strangely pulls to the left.

After this had been done, the ride is much smoother, the road noise is lower and I am now averaging around 49-55mpg.

I am going to run the car for a couple of weeks, check the mpg and feed this back to the fleet company.

[PeteB]

... tracking was spot on but the car still strangely pulls to the left...

this may be due to the camber in the road (to help water drain off) - it's often almost imperceptible, and also we're all so used to it we hardly notice it, but it can be enough to make the car steer slightly left

[johalareewi]

I am going to run the car for a couple of weeks, check the mpg and feed this back to the fleet company.

Are the tyre pressures high enough?

Even slightly underinflated tyres on a prius can make a noticable dent in the mpg.

[kevin h]

I always re-inflate the tyres and ask about the oils before and after a service.

60k on the clock now and getting in excess of 70mpg from a tank full.

never gun the car and rarely exceed 67mph (funny speed but it works for me) on the motorways.

25 mile round trip to work every day which is country and a bit of stop start town driving.

Still happy !!!!

[seamus1]

Ive had the new tyre format for a week now and the last fill only gave me 45mpg which I consider very poor.

The Eco Drive Level on the dashboard just doesn't go anywhere above 45/46mpg even on long drives of 30/40/60 mph. Before the display would change constantly even upto to 70mpg.

Its very strange, the only other thing that has been changed is this ECU update for the Battery discharging, can this be having a negative effect?

[Grumpy Cabbie]

It might. It's probably just finding it's feet again. Give it a couple hundred miles and see if that helps.

Alternatively, did they leave your car doors sat open for 3 hours whilst they faffed about, running your 12v low or flat. The 12v is weak and doesn't like being run low. Give the car a good run and see if things improve.