Miles per gallon

Q I purchased a 2003 Jaguar X-TYPE 3.0 V6 petrol automatic recently and the typical mpg as set with either A or B setting for the mpg are only around 19.6mpg. I have replaced the air filter and had an oil change. The current MOT which was carried out some five months ago stated a fairly low C0 reading of 0.2 – naturally I can get this rechecked. Is there a test method or ECU adjustment to gain more mpg?

Also, what other comments would you kindly suggest to increase MPG? I realise the fact that it is a 3.0-litre automatic but would be happy to consider improvement.

Should I use E5 or E10 unleaded and would either improve performance?

I have been told that some additive may improve the MPG – can you suggest a suitable type that I may try?

The tyre pressures the Haynes manual states should be at 36psi front and perhaps same for the rear with little load – is that figure correct?

Chris Toomer A If I start with your last question first. The tyre pressure settings I have for your Jaguar are for the 16in rims is 32psi front and rear, and for the 17in rims is 30psi front and rear, and for the 18in rims is 36psi front and 34psi rear. Although I would note the tyre pressures in the vehicles handbook as you may have different setting for town and motorway driving.

On the subject of the fuel, E5 will give a better mpg reading than the E10 as it is a more efficient fuel, and as all the E5 now available is the higher-grade fuel, this would give the best mpg figure without the need of additives.

You do not mention the types of driving you are doing, but if this is mainly town work then the 19.6mpg figure you are getting would seem reasonable from the Jaguar V6 petrol engine.

Having owned a S-TYPE Jaguar with the V6 petrol engine I know that the standard figure I achieved was around the same

mark, with a figure of around 30mpg obtainable on a long run with thought to the throttle position. The A and B setting will only calculate the average mpg and so it would not be expected for these reading to be too far apart.

The ECU is not adjustable and calculates the desired fuel mixture, and any attempt to weaken the mixture would be detrimental to the running and the longevity of the engine.

So, to summarise the best action to receive the best miles per gallon return figure would be to use the premium E5 fuel and drive with economy in mind.

Q Could you please advise on the following, regarding service miles verses age of components/fluids please? I’m in a dilemma at the moment planning vehicle future service items, etc., on my 2015 Audi Q5 S line 2.0 TDI with a total mileage of 27,000 miles. Presently my annual mileage covered is around 3000.

The components/fluids involved are: Checking DPF – Audi recommends 114,000 miles. Replacing air filter element – Audi 57,000 miles. Fuel filter – Audi 38,000 miles. Transmission oil and external filter – Audi 20,000 to 36,000 miles. Tyres age five years – presently all Michelin LS3 fitted. Transmission rear wheels final drive oil? Aircon service? Changing brake fluid – Audi two years: note at each service moisture content seen as only >1%.

I have recently changed the cambelt, water pump, tensioners, plus auxiliary drive belt. Also, I do have Audi services annually changing engine crankcase oil/filter and general checks.

Thanking you in advance for your time. Tom Heron A I would first say that the low mileage you cover is the biggest problem for a diesel engine fitted with a DPF. The advice I would give would depend on if the mileage covered is carried out over many short distances or is the result of infrequent use, but on longer runs. The latter being the least detrimental to the engine.

The DPF may need forced regeneration if the vehicle is used on shorter journeys which do not allow the system to get up to temperature and complete the regeneration process itself.

The air filter is something that can be easily checked and it should be simple to ascertain if the filter looks to be grimy, but I would not normally replace an air filter on a time basis, but purely on the mileage covered. Deterioration over time is not normally a concern for the air filter.

The fuel filter as it would still be the original unit, I would consider renewing although this is earlier than suggested – the filter on your Audi is a metal cannister type and this will ensure that corrosion does not begin to affect the casing.

The service interval I have for the transmission on your Q5 is 40,000 miles, and I would stick to this regardless of the time frame.

The tyres I would start to check thoroughly after six years. Any cracks in the sidewalls would indicate that the tyres would need to be changed. The aging of the tyres will vary depending on the conditions they are exposed to. If the vehicle is kept garaged or out of direct sunlight when not in use this will help prolong the useful life of the tyres.

If you still have the original tyres on after covering 27,000 miles, I would expect the tread to be getting near to the point when you may wish to replace them – if they have been changed at some point then they will have a few years left in them. The date of manufacture of the tyre can be checked by looking at the four-digit code on the tyre – the first two digits are the week and the second two the year, so 2217 would indicate that the tyre was made in the twenty second week of 2017.

There is no specification for the final drives and I would expect these to be OK and on a mileage basis may consider around 60,000 miles regardless of time, to be a good service period.

The air-conditioning service will normally need doing every three years regardless of miles, as will the brake fluid change. Both of these are prone to deterioration on a time basis.

As mentioned earlier, it would also be beneficial if the journeys covered are normally quite short distances, to give the Audi a good run where motorway speeds could be maintained for at least 30 minutes every six months or so.