Rover 25 - poor mpg

[MartinQ]

The wife's 25 is getting very poor economy - at the last fill up it was 32mpg, although I have seen 27mpg in the past. It's the 1.6 so was expecting around the 40 mark.

It's been serviced recently with new oil + filter, plugs, air filter and had the head gasket replaced last month.

It's not driven hard - in fact she never takes it over 3k rpm in case it damages something. Unless she's telling porkies, is there anything else I should look at?

Thanks all.

[MGJohn]

It could be something as simple as a worn CTS ~ Coolant Temperature Sensor. They do not last forever. Could be sending engine "always cold" information to the ECU all the time which if it no longer reads the coolant temperature correctly, leads to continuous over overfuelling. Sooty exhaust pipe and spark plugs can indicate that.

Cold engines need extra fuel to start and get going. When up to operating temperature, the fuelling is progressively reduced until fully warmed up. In the fully warmed engine if the sensor is still reading 'cold' .....

Removal and refitting a replacement is a five minute job on your car. Get an OE ( MG-Rover ) genuine replacement as some after market alternatives can fail prematurely leading to exactly as you describe.

There again, someone who drives your car may have acquired a heavier right foot ... 'appens....
.

[Mr2Mike]

What kind of use does it get, short trips in the city or long motorway blasts?

[MartinQ]

My wife commutes about 8 miles each day, mainly on NSL A roads.

I'll get a new coolant temp sensor and see if it makes any difference.

Thanks.

[Mr2Mike]

If the head gasket failed to the point the cylinders where getting coolant in them then the it can very often kill the lambda sensor, and this will have a significant impact on economy. Of course they also die just from old age.

Edited by Mr2Mike on Wednesday 19th May 17:41

[tali1]

MartinQ said:

My wife commutes about 8 miles each day, mainly on NSL A roads.

I'll get a new coolant temp sensor and see if it makes any difference.

Thanks.

For that level of low mileage per day anything over 30mpg from a 1.6 is free motoring
You want heavy MPG from a 1.6? -try 16mpg urban from my Montego 1.6HL

[ROB8 F]

My MG ZR 1.4 Has seen 22mpg in the past
I blame Rovers tendancy to cut corners, Lack of efforts to improve economy in any way are clear.

[robgee1964]

MartinQ said:

The wife's 25 is getting very poor economy - at the last fill up it was 32mpg, although I have seen 27mpg in the past. It's the 1.6 so was expecting around the 40 mark.

It's been serviced recently with new oil + filter, plugs, air filter and had the head gasket replaced last month.

It's not driven hard - in fact she never takes it over 3k rpm in case it damages something. Unless she's telling porkies, is there anything else I should look at?

Thanks all.

My Mother had a 2001 1.4 25 which would only return low thirties if used for trips of 5-10 miles or so. If you did 15-20 miles it soon got to early 40's.

The question is has it suddenly got like that, or did it suddenly go worse. Failed lambda sensor could mess it up but for a first port of call do a full service including plugs, and air filter.

Whatever you do don't start "guessing" with possible EFI problems, usually its cheaper in the long run to get the car diagnosed by a competent fuel injection specialist, but do make sure its someone who knows what they are talking about.