Honest John: is a diesel-engined VW Golf a safe bet in the long term? 

The portable emissions testing system (PEMS) is seen attached to the exhaust of a red 2016 Volkswagen AG Golf TDI emissions certification vehicle being tested inside the California Air Resources Board Haagen-Smit Laboratory in El Monte, California, U.S., on Tuesday, Sept. 22, 2015. The VW vehicles were programmed to activate pollution-control equipment while being tested for compliance with EPA and the California Air Resources Board standards, ensuring that emissions met legal standards; afterward, the car's software switched off the controls so the cars’ performance was maximized while allowing far higher pollutant levels. Photographer: Patrick T. Fallon/Bloomberg
A Volkswagen Golf undergoing emissions testing. Irrespective of the VW 'cheat' scandal, is it a good idea to buy a diesel to keep for many years?  Credit: Patrick T. Fallon/Bloomberg

If your car has developed a fault, or for consumer advice, turn to Honest John by emailing [email protected]

Fuel for thought

My annual mileage is low, so I’m thinking of buying a VW Golf Mk6 that I would like to keep for some time. However, I’m not sure whether to go for a 1.4-litre petrol-engined version or the 1.6-litre TDI diesel. I have been told that diesel engines last longer (up to 200,000 miles) and that the cars are cheaper to tax and maintain, but I’m worried that they may be increasingly persecuted by emissions legislation. Can you enlighten me? PJ

Diesel engines used to last longer when they were simple, but not any more. And now they are saddled with all manner of emissions-scrubbing devices, the failure of which massively increases the running costs – especially if you buy one at three to five years old and the emissions equipment starts to play up. Note that it is illegal to adapt or remove the emissions equipment that are car was homologated with. My general advice is that if you do fewer than 20,000 miles a year, don't get a diesel.

Spokes person

Is there a good reason why you don't see VW T-Rocs carrying bicycles? Credit: Max Earey

Can you tell me why it is advised not to fit a rear-door bike carrier to the Volkswagen T-Roc? The only explanation I can find online is that it is due to the design and/or strength of the tailgate. Dealerships are equally vague and suggest using roof bars or a tow-ball attachment. RB

I've never been keen on bike racks slung on to hatchbacks, because some can't take the weight. The answers are to fit a towbar, then use a Thule bike rack or similar that fits on the towball. Or use roof-mounted bicycle carriers.

Film noir

I collect my Motability-sourced Mercedes-Benz GLA very soon. Motability has told me it is prohibited for a dash-cam to be wired to the fusebox, however, while Halfords has advised my unit cannot practically be installed by connecting to the cigarette lighter. Any ideas? GM

I don't know of any dash-cams that can't be powered from the 12v accessory socket. They can be wired into the car, but if Motability prohibits it on a leased vehicle then I'm afraid you'll have to abide by that rule.

Revolution revelation

Is the gearing on some diesels too high? Mine runs at 1,500rpm in eighth at 70mph and I have noted that some run at 1,200rpm in top gear at 70mph. I ask because my dealer technician recommends running diesels in ‘sport’ mode, even on a motorway at the legal limit. KR

Sensible advice. You don't want to run a diesel at less than 1,500rpm or it won't properly regenerate its diesel particulate filter (DPF). My Renault Koleos runs at 2,200rpm at 70mph and I never have any DPF problems.

The end game

Tread carefully: tyre safety advice should be followed Credit: JOCHEN LUEBKE/AFP/Getty Images

I would like your opinion on Costco tyre-changing policy. I have been told that if you want two new front tyres they will only fit new tyres to the rear. I was wondering is this for a safety issue and, if so, could you explain it? AB

It’s Tyre Safety Council advice to help prevent rear tyres losing traction when braking into corners in the wet.

Neutral territory

I have a 2010 Mercedes E350 estate that has on three occasions dropped out of gear while travelling at low speed. It happens in forward drive and reverse. The garage that regularly services it put it on test, but could find no fault. Is it telling me that it is time to get rid, or can it be fixed? It has the steering column selector lever with paddle levers for manual control. ER

It probably needs fresh fluid. The dealer might tell you the transmission is 'sealed for life' (because he wants to sell you a new transmission). You need to contact www.fedauto.co.uk to find a member that has a Liqui Moly Geartronic transmission fluid dialysis machine.

Feeding the Cat

I own a Jaguar XE 2.0-litre petrol. The handbook says to use 95 Ron unleaded for optimum performance, but adds that 98 Ron is an acceptable alternative. Tesco Momentum appears to be 99 Ron. You consistently recommend a higher grade. Is that still the case for my vehicle? EB

Yes. Use any branded super, preferably Shell V-Power, BP Ultimate, Esso Supreme, Total Excellium or similar. On 95 Ron, engines lose a little power and torque. Don't buy an expensive car then try to save money on fuel. It’s a false economy that might cost you in the long run. Also, don’t pay more than £1.50 a litre for superunleaded.

Not connected

I have received a letter telling me that my 2011 BMW 320i is subject to a safety recall. If this does not happen before it is due for its next MoT, will the car fail? PB

Unlikely. It will be to check a wiring connection that can leave some E90 models with no electrical power (and thereby stranded).

Another new acronym...

I see the latest Mercedes C-class is to be fitted with a petrol particulate filter. Do you have any knowledge or experience of this, and is it similar in usage to the diesel particulate filter that forces you to use the vehicle for long journeys at regular intervals? We use our car for about four miles a day with the odd longer run. DB

Virtually every new petrol-engined car had to have a petrol particulate filter (PPF) from September 1 to help in the new WLTP fuel economy and emissions test. They are usually located close to the combustion chambers, are thereby self-cleaning and have far less soot to deal with then the equivalent filter in a diesel engine. I don't foresee problems, but we shall have to wait and see.

Volkswagen gulf

I have a VW Golf GTI with a retro-fitted Garmin satellite-navigation system, which includes a speed icon. This runs consistently 4mph slower than the VW speedometer. Which is likely to be the more accurate? CM

The sat-nav. On a straight, level road with a clear signal path from the satellites, it gives you an extremely accurate reading. Car speedometers usually over-read.

Change of name

I have a Toyota Auris 1.8 hybrid on a PCP that ends soon. I am happy with the car, but note it rarely gets a mention in your column and generally gets only semi-positive reviews. Is there something better I should consider before buying another Auris? DW

It is regularly mentioned in outgoing emails, but if readers’ questions are too lengthy they aren’t selected for the published column. It has proven reliability, is very well built and gets a three-star rating (from five) on the HJ website. It’s also still the only hybrid in its price range, though others are on the way. An all-new Auris hybrid, arriving by the end of the year, is returning to the worldwide model name ‘Corolla’.

Slow to adapt

We have a VW Golf 2.0 GT TDI 140 manual, registered in January 2009. It is one of the vehicles affected by the emissions scandal, but on the advice of a mechanic we did not take up the adaptation offered by VW. The car has covered more than 80,000 miles and runs very well and economically. It is probably the best car we have ever owned and we had no intention of changing it. However, we are concerned that it might not pass the emissions test of the new MoT. Would using AdBlue help? Or would you recommend changing the vehicle while it still has some value? CH

You cannot use AdBlue in a car that does not have a selective catalytic reduction system. Either have the VW NOx update, because VW has pledged to fix any consequential problems, or try to part-ex the car. You will get a better resale value after the NOx update. 

Too good to be true?

I am thinking of buying a used Mini Clubman with a petrol engine, and happened to come across the Motorpoint website. Comparing their prices with dealers, they appear to be very competitive. Why would that be? RR

The way they buy cars – sometimes ends of lines, sometimes unsold over-age stock, sometimes minor trim misbuilds, not 100 per cent to UK specification, and sometimes bulk buys, whether new or from fleets. Just ask sensible questions and beware of evasive answers to make sure you get what you are paying for.

If your car has developed a fault, or for consumer advice, turn to Honest John by emailing [email protected]

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