Agree 100%, if it's under warranty you'd be a LOON to do anything than the recommendations.

I would concur, diesel engine oil is high in detergent which helps keep the engine clean but most modern diesel servicing schedules leave the oil in for far to long, change it now if you want the engine to last.

The temperatures effect on fuel consumption was well illustrated in May this year when we went to the far north of Scotland, on the way up the temperature was just above freezing and my average consumption was just over 60 mpg, halfway through our holiday the temp shot up to 25C+ and on the return journey averaged 67.3. over about 650 miles.

The car was a Peugeot 406 2.0.Hdi and I do drive very carefully, rarely over 60 mph or 2000 rpm.

Has your mpg dropped from 68 to 51 or are you saying you are not getting the EU official average of almost 68 mpg. From your original psot its not clear.

The official combined average for a Suzuki Swift diesel is actually 67.3 mpg. If you were getting 68 mpg you were one of a very small minority of car owners actually bettering the official combined figure. In all the cars I have owned the only time I have approached the official ombined is on a very long (400+ miles) run in good conditions mainly on motorways.

In the real world the most people get is about 20% under the official combined, this calculates as 53.8 mpg.

So I honestly think there is nothing wrong and you were expecting more than was realistically possible.

Edited by skidpan on 30/12/2012 at 13:58