Michael McAleer answers your queries
From Joe Grealy:
I drive a Kia Sorento SUV 2.5-litre version. It's good on fuel consumption, but because I travel a lot my fuel bills are very high. Could I purchase vegetable oil and mix it with ordinary diesel fuel with negative effects on my engine? What proportion of vegetable oil to diesel would work?
Tim O'Brien, our colleague who has converted his VW Passat to run on vegetable oil, tells us it is technically possible to mix about 5 per cent vegetable oils with diesel and the engine will still run. "However, the long-term effects of this are, at best, not known and there will be warranty issues," says Tim. "If, however, warranty is no longer an issue, then for best results get a conversion kit from a supplier who will guarantee the kit, such as Elsbett in Germany. The Irish company ecocar.ie will supply the kit and guarantee the work fitting the car. Complete package costs from about €1,700 but if you have an SUV and do high mileage it is probably well worth it." See ecocar.ie or eilishoils.com or elsbett.com
From Michael Leonard, Co Wicklow:
Regarding the disposal of old cars (Motors, September 21st), one of my children living in Canada has just disposed of her 1986 Tercel. There, the Kidney Foundation collect old cars (maybe there is a small fee). They recycle them and the proceeds fund research work. Is that not a more positive approach?
It sounds like a viable proposition, but it would be up to the charities to get the initiative off the ground here, perhaps with the help and support of one of the car distributors.
From T O'Boyle:
What is the point of the small roundabouts that are springing up in our estates these days? At the entry to our estate, someone - the council or the builders - have created this painted mound around which we are expected to drive.
The problem is that the flow of traffic from the main road to the left means that at rush hour, when we're all going to work, it becomes a regular T-junction. All the 'mound' does is offer a wake-up jolt as one of your wheels passes over it. Is there a special rule for such roundabouts?
In short, the answer is no. These painted circles were part of an engineering fad some years ago, but generally there has been a realisation that they really don't work.
They serve, in some instances, to slow traffic as confused drivers brake and try to work out what's going on. However, if the aim is to assist the flow of traffic, then in most instances it merely serves to confuse.
However, it could be worse. You could live in Swindon. Reader Maria Walsh sent us images of a traffic system that would seem to be unrivalled for its ability to confuse and scare motorists.
Known as "the Magic Roundabout", it comprises a main roundabout surrounded by five mini-roundabouts. It has apparently become something of a tourist attraction.
No doubt we will see something similar here in due course, if our track record for traffic management is anything to go by.
Send your queries to Motors Help Desk, The Irish Times, Fleet St, Dublin 2 - or email to motorshelp@irish-times.ie