Increased Fuel Consumption following Full 60 Service

[BoutTime]

Hi All,

A few weeks back my CT went in for it's Full 60 Service. I believe the plugs are changed at this point and I was expecting (if anything) the fuel consumption to improve.

Bizarrely after collecting the car I noticed a drop in the reported mpg. I've always been impressed with the mpg of my CT. In mild weather I've managed in excess of 70mpg a few times (72.3 being the best on a trip to the coast and back) but generally I get over 60. After swapping to Michelin Cross-Climates this dropped by a couple but the improve in ride was a price worth paying.

After filling up with E10 fuel last week the mpg has dropped further and on the school run where I'd regularly achieve 60+ I'm now down to around 54mpg. I've now just filled up with Shell V-Power a couple of days ago which is E5 and I've noticed no improvement. So considering I first noticed a decline in mpg immediately after the service I'm wondering if Lexus do anything to the car at 60k miles which would effect the fuel economy. Such as re-programming the battery/hybrid system in order to preserve the life of the Battery. I'll likely contact the dealer and ask the question but thought I'd post here first in case anyone else has had a similar experience.

Cheers.

[ColinBarber]

You certainly shouldn't expect an improvement in mpg after a service if you keep to the schedule - the service schedule is designed to replace parts before they degrade the operation of the engine/vehicle (e.g. the plugs would probably go on for another 40k miles without issue, although you start to run a slight risk of tips breaking off and causing damage to the cylinders).

The dealer may have disconnected the Battery during the service - a reset of the ECU will mean it could take a couple of weeks to relearn everything back to your driving style.

[rayaans]

More likely that a drop in temperature cause it 

[BoutTime]

1 hour ago, rayaans said:

More likely that a drop in temperature cause it 

I've had this car over two years so I'm aware of how temperature can affect fuel consumption. I monitor fuel consumption on each trip and factor in ambient temps. Like for like, there is a decrease in fuel economy. And I noticed it on the way back from the service.

[Las Palmas]

3 hours ago, BoutTime said:

In mild weather I've managed in excess of 70mpg a few times (72.3 being the best on a trip to the coast and back) but generally I get over 60. After swapping to Michelin Cross-Climates this dropped by a couple but the improve in ride was a price worth paying.

Which tyres did you have before the CC?

Better fuel consumption than with Michelin?

We have Pirelli P7.

[BoutTime]

3 minutes ago, Las Palmas said:

Which tyres did you have before the CC?

Better fuel consumption than with Michelin?

We have Pirelli P7.

Yokohamas front and Nokian rear. The Michelins are much nicer tyres but fuel consumption is a little worse.

[rayaans]

1 hour ago, BoutTime said:

I've had this car over two years so I'm aware of how temperature can affect fuel consumption. I monitor fuel consumption on each trip and factor in ambient temps. Like for like, there is a decrease in fuel economy. And I noticed it on the way back from the service.

I presume you also measure the ambient humidity whilst doing your calculations?

[BoutTime]

12 minutes ago, rayaans said:

I presume you also measure the ambient humidity whilst doing your calculations?

You presume wrong as I don't do any calculations. I use the onboard computer. I simply compare trips like for like so it matters not whether the computer is accurate. It's the delta I'm looking at. It's really quite simple. Since the service my car is using noticeably more fuel.

[diabolik]

E10 fuel usually increase the fuel consumption and it takes about 3-5 top ups to notice the difference. 

[BoutTime]

I appreciate the comments all. But when I picked the car up and drove it home E10 fuel wasn't in use. 

[rayaans]

15 hours ago, BoutTime said:

You presume wrong as I don't do any calculations. I use the onboard computer. I simply compare trips like for like so it matters not whether the computer is accurate. It's the delta I'm looking at. It's really quite simple. Since the service my car is using noticeably more fuel.

But that's what I mean. The computer doesn't take into account humidity or temperature or any other variable like tyre pressure. It could be a number of things 

[BoutTime]

1 minute ago, rayaans said:

But that's what I mean. The computer doesn't take into account humidity or temperature or any other variable like tyre pressure. It could be a number of things 

Like many people, the journeys I make are repetitive. I reset the computer pretty much every journey. Iv over two years experience driving the same journeys in the same car in all different weathers. So I've a very good understanding of what mpg I should expect.

I've noticed a significant difference from the moment I collected my car from its Full 60 service. I don't know what is in the volatile memory and what is in the non-volatile computer memory. But everything was displayed as normal when I collected the car. So no evidence of the ECU being reset. Perhaps it was. I can't be sure.

[royoftherovers]

Could your brakes have been adjusted unsatisfactorily during service, so much so, that they are binding thus leading to increased fuel consumption ?

[Las Palmas]

21 hours ago, BoutTime said:

Yokohamas front and Nokian rear. The Michelins are much nicer tyres but fuel consumption is a little worse.

Always had 4 tyres same brand, same pattern in all cars we have had. Do not believe mixing is good.

[BoutTime]

Just now, Las Palmas said:

Always had 4 tyres same brand, same pattern in all cars we have had. Do not believe mixing is good.

Agreed. That's why I changed them. You are unlikely to find a dealer change all four tyres when only two are worn on a car they are selling.

[Las Palmas]

11 minutes ago, BoutTime said:

Agreed. That's why I changed them. You are unlikely to find a dealer change all four tyres when only two are worn on a car they are selling.

I would expect a pro selling cars with same tyres in each corner.

[BoutTime]

46 minutes ago, Las Palmas said:

I would expect a pro selling cars with same tyres in each corner.

I purchased the car from an Approved Lexus dealership. Margins are very small on a used car of that value.

[LexusDave]

I’m surprised no one has mention oil. There’s been a number of reports on here in the past about how not using the correct oil can damage fuel consumption. The spec for the CT, and in fact most of the Toyota and Lexus range, is 0/20 but on occasions the dealers have been known to put 10/30 or similar in as 0/20 isn’t available. I believe this can have a detrimental effect on consumption by up to 5%. Check with your dealer to see what they used.

[Mikey B]

Have you checked the tyre pressures?  I tend to run mine at the suggested pressure for fully loaded, but notice that they tend to set them to the lower number when its serviced

[ColinBarber]

1 hour ago, LexusDave said:

I’m surprised no one has mention oil. There’s been a number of reports on here in the past about how not using the correct oil can damage fuel consumption. The spec for the CT, and in fact most of the Toyota and Lexus range, is 0/20 but on occasions the dealers have been known to put 10/30 or similar in as 0/20 isn’t available.

It's a good point, and something that has caused issues in the past. I cannot believe that dealers would still get this wrong a decade after the CT launched, given that virtually all current vehicles use 0/16w or 0/20w oil so they should always have plenty.

Certainly worth asking, but I doubt they would admit the mistake even if they knew they had put in the wrong oil 😞