Sudden drop on petrol consumption

[rhosneigr]

As per heading, a month ago I decided to give the car a treat and put a tank full of premium fuel in. The consumption on that tank full fell to 38 mpg from the 47 I was getting previously. Filled again with normal unleaded a week ago and the consumption shows 39 mpg over the last 40 miles or so. I realise that the outside temperature has dropped but I've had this car over 3 years and has never dropped this low. The journeys I do are similar every year. Any ideas please? The car seems to have a definate flat spot when accelerating from cold but then is OK when warmed up so wondering if this could have anything to do with it. The average consumption over the last couple of thousand miles has been 47.7. 

[ISJason]

Hi. You will get different mileage figures in different seasons. I get lower in my RX400h in the winter than the summer for instance. Just a thought.


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[Britprius]

39 minutes ago, rhosneigr said:

As per heading, a month ago I decided to give the car a treat and put a tank full of premium fuel in. The consumption on that tank full fell to 38 mpg from the 47 I was getting previously. Filled again with normal unleaded a week ago and the consumption shows 39 mpg over the last 40 miles or so. I realise that the outside temperature has dropped but I've had this car over 3 years and has never dropped this low. The journeys I do are similar every year. Any ideas please? The car seems to have a definate flat spot when accelerating from cold but then is OK when warmed up so wondering if this could have anything to do with it. The average consumption over the last couple of thousand miles has been 47.7. 

The figures you quote sound about normal to me. My previous car a Prius on witch the CT is based varied by around 10 mpg from summer to winter. The Prius however returned about 55 mpg winter, and 65 mpg summer. There were some occasions in the summer when I achieved 72 mpg per tank giving a range of over 700 miles.

John.

[mandon75]

I thought it was a well known fact that your MPG reduces during the colder months.

I asked my dealer why the CT, having the same hybrid system as the Prius, gave poorer results in MPG. Their response was that the CT is a luxury car and the quality of products add weight therefore affecting MPG.

[rhosneigr]

It may well be that it's well known that consumption drops in the cold weather, but as stated in my post I've had this car for 3 years and last year's weather was colder than it has been up to now this year so why the sudden drop. I think the dealer is talking rubbish. 

[Mikey B]

Tyre pressures?

[Wass]

Sadly, the motor trade has been doing this sort of thing for many years. ( using the cheapest available fluids  and charging for premium) Softening tyre pressure slightly in order to improve the smoothness of the ride and reduce road noise. It is perhaps fortunate for us that it is now far more fashionable to buy cars for their efficiency appeal.

So as soon as fuel consumption gets worse, we are looking for causes. Causes may be the wrong grade of oil , lower tyre pressures,  or more mechanical faults such as lack of compression due to worn valve seats or piston rings, faulty charge air temp sensor, binding brakes, worn wheel bearings ... the list is almost endless however.... sadly when the car returns from service using more gallons of fuel per mile than before it went for service, it does point the problem back to the servicer with there being an outside chance that a fault may suddenly have developed during the service work. In the case of Lexus and Toyota cars though, the probability of the sudden true fault developing is minimal due to their reliability record.

[rhosneigr]

Thanks for your replies. Tyre pressures OK at 32 psi. The car has only done 14k from new and I've been the only owner but Wass may have hit on something when he mentions the car going for service. The consumption did drop a little following the service in July but not to this extent. I will go and have a word at the dealership in the New Year. 

[royoftherovers]

I`ve had my car for 5 years plus and my consumption has increased to 27mpg (from 33mpg). I put this down to the colder weather and the more local commutes.

The car sounds and performs as it has always done. A gem.

[Firecat]

Hi,I have a 2014 ct200h f sport with 40,000 miles and average 57mpg in th summer and this drops to 53 in the winter averge on trip computer is 56.5mpg over three years of ownership. I've seen over 60mpg on long congested motorways averging about 60-65 mph.These are a mixture of motorway, A and B rds, admittedly these are the trip computer figures so may be obtermistic!  

[Wass]

On 12/27/2018 at 8:14 PM, mandon75 said:

I thought it was a well known fact that your MPG reduces during the colder months.

I asked my dealer why the CT, having the same hybrid system as the Prius, gave poorer results in MPG. Their response was that the CT is a luxury car and the quality of products add weight therefore affecting MPG.

The prius may be a little lighter , however, the major different is drag coefficient. Latest prius is .24CD and latest CT is .28 CD