Hi Paul, I read your article on cold start idling which is intended to warm the engine. I also noticed that the car owner mentioned “hesitation” as a recent problem.
I think you should also warn readers out there that hesitation is sometimes a result of using adulterated fuel.
Three weeks ago my 2000CC Premio had trouble with acceleration after a cold start and could not reverse uphill without running the engine for five minutes.
My mechanic recommended a fuel pump check, but he later called asking where I fueled my car from. I did not think that mattered anyway.
He instructed me to empty the tank at any station and refuel from particular stations.
He was not too intent on explaining anything apart from calling him back and explaining to him how the car had responded.
Indeed the car, as I explained to my mechanic, had started without and with a powerful acceleration.
My mechanic then rolled me down a lecture and told me I had been running on a mixture of petrol and kerosene, and that’s why the engine was hesitating and I could not accelerate properly, especially when the AC was on.
He suspected that the adulteration got worse when prices of fuel went up, making the problem in the fuel too pronounced that I could barely miss it.
The problem did not recur and I switched fuel stations since then.
The only scar left behind by this mishap is the white smoke that I have to contend with for almost a minute during cold start in the hot afternoon. My mechanic asked me to take a chill-pill on that one. Luke Mawnda
Hello Luke, your mechanic is right, one of the causes of gasoline (petrol) or diesel engine hesitation and poor performance can be fuel adulteration.
Adulteration of gasoline and diesel is commonly among unscrupulous fuel dealers mostly in third world countries.
Uganda National Bureau of Standards has acknowledged this problem and put down measures to combat the vice.
Adulteration of fuels deprives motorists of assured quality, loss of revenue and damage to vehicles and the environment. It also introduces foreign substances into fuel and the resultant product does not conform to vehicle specifications.
Adulterants alter and degrade fuel quality and performance.
To understand the gravity of this problem one needs to appreciate that different fuels such as gasoline, kerosene and diesel are a byproduct of refining or separating the many compounds in crude oil which is a mixture of different hydrocarbons formed by decomposition in the earth’s surface.
Some of the main products of the refinery process in East Africa are gasoline, diesel and paraffin.
Gasoline is a mixture of hundreds of hydrocarbons with different boiling points. It boils and distills over a lower range of temperatures starting at 85 degrees centigrade.
It has a lower flash point (low flammable) and ignites faster. Kerosene which can be obtained from distillation of crude and thermal cracking of heavier petroleum products is a lighter end of a group of petroleum streams or middle distillates which burn at higher temperatures between 150-275 degrees centigrade.
Critical to note the density, vapour pressure and flash point of gasoline and kerosene are different. These qualities of fuels are important in determining prompt ignition and efficient burning of fuel in internal combustion engines.
Gasoline fuels such as those sold at Shell are blended with anti-cylinder knock agents (high octane Shell V-Power), anti-oxidants, metal deactivators, anti-rust additives, pre ignition additives and upper cylinder lubricants (friction modifiers in Shell FuelSave).
This ensures prompt ignition of the engine, clean and efficient running as well as engine protection. The effects of adulteration of kerosene and gasoline reverse the benefits of good gasoline fuel to an internal combustion engine and the environment. Adulteration leads to increase of harmful tail pipe emissions and carcinogenic toxins.
This is because of higher levels of hydrocarbons, carbon monoxide and (nitrous oxide) NOX gases.
This environmental challenge is worsened when catalytic converters are damaged or deactivated due to the adulteration.
This lowers the conversion of emission pollutants. Adulteration affects octane quality (how slow fuel burns) which falls below the octane requirement oran engine which can cause severe engine cylinder knock or reduced efficiency and performance.
Kerosene adulteration in gasoline will lead to deposit formation in fuel injectors and on intake valves which also lead to reduced engine performance and fuel economy as well as high maintenance coats.
Why fuel is adulterated
The primary factors that give traction to adulteration include the existence of different tax levels amongst the fuels, intermediate and by products.
Fluctuation in pricing of fuels due to market and supply conditions and easy availability of adulterants. Limited capacity to monitor all fuel vendors and retailers around the country’s as well as a limitation of mechanisms and instruments for spot checking the quality of fuels.
Your mechanic recommended Shell as one of the fueling options because Vivo Energy, the downstream distributors of Shell fuels and lubes in Africa have introduced stringent safeguards and checks in their fuel supply chain.
The use of dedicated modern fuel laboratories which issue certificates of worthiness after testing samples of fuel at loading points in Kenya and offloading points at depots in Kampala and Mbale.
The mandatory testing for adulteration of all fuel products delivered at all Shell sites around the country by quality marshals.
The continued random testing of fuel samples at different Shell sites around the country by a fleet of mobile laboratories.
This is in addition to continuously innovation of fuels that improve the performance and protection of your car.