He said: "I'd like to say from worst to best you're saving at least 40% of your fuel - maybe more."
But Karl added: “People shouldn’t put themselves at risk when hypermiling.
"It should be done safely within the road conditions and should be a safer way of driving as you’re aware of road and traffic conditions and using them to your advantage.
"The key is being sensible, for a lot of people hypermiling should just be common sense and a lot of people do it already without knowing – treating every drop of fuel like it’s your last is a great way of really focussing on keeping efficient."
1. “Before you even turn the key, ensure your car is fully maintained as if you abuse your car and never service it or change the oil it’s not going to run at peak efficiency - and check the tyre pressures as a lower tyre pressure means increased drag and means you’re using more fuel to turn."
2. "You can reduce weight if you’re carrying around items that could be heavy which don’t need to be in the car – removing roof and bike racks, roof boxes, it all make a difference and reduces aerodynamic drag without even getting in the driver's seat."
3. “If you have to put fuel in, make sure you’re buying it from the cheapest place in your area by using an app like PetrolPrices.com, if you can get fuel for 5-10p a litre cheaper and you can see that on a map then that’s brilliant."
4. “Choose your route as it might only be five miles to work but that might be through a busy urban area with lots of stopping and starting - there might be a longer route with less start-stopping which is a more consistent drive not on the brakes or accelerator which means it can be more efficient to go the longer way."
5. “Once you’re in the car, the key thing to hypermiling is anticipation as it’s about driving to the road, traffic and weather conditions – you can minimise the use of brakes and accelerator and drive smoothly which means you can utilise other hypermiling techniques like coasting.
“If you can see a Stop sign before you come to it you can slowly ease off in plenty of time, if you’re in-gear coasting in most modern cars you don’t use any fuel whatsoever and the smoothness makes driving a much more pleasurable experience.
6. “Another thing to point out is speed – travelling at 56 miles-per-hour as opposed to over seventy can save up to 35 percent in fuel and means you can do other things like slipstreaming where you use the car in front to part the air and create less aerodynamic drag on your car.
“If you are slipstreaming, you can do this behind HGVs but it needs to be a safe distance away taking into account road, weather and traffic conditions, following the two second rule that’s enforced by road safety laws.
7. “Coming into the summer, there’s a few things you can do to help yourself – parking in the shade means when you get in the car you don’t need to reach for the aircon which can sap anything up to ten percent of the fuel efficiency of the vehicle.
"Driving at anything under 40 miles-per-hour it’s more efficient to have the windows open but anything over 40 is probably better to have the air-con on, and if you're going to have the air-con on you should use the recirculation button so it cools down air that’s already in the car."