Recognizing fuel problems in cars and light trucks

Cars and trucks operating properly and running on good in-spec fuel should give you great performance with a minimum of problems (most of the time).  When your car starts giving you problems, you know it. Something doesn’t seem right. Or it’s not running the same way it did last month.

If you’re in that position, the problem is either going to be mechanical or it’s going to be fuel-related.  If it’s fuel-related, it’s an easier fix, so that’s what you hope for. But how do you know? There are so many things that can go wrong with a vehicle, unless you’re a seasoned mechanical pro, you probably don’t know what to look for or what to do about it.

It’s impossible to go through every single possible cause/effect here. But it is possible, here, to give some guidelines on what to look for and how to recognize a problem that may be more likely to be fuel-related. For many problems you may encounter, they can just as easily be caused by a fuel problem as a mechanical one.

Change In Performance or Starting

Any time there’s a change in performance for your vehicle, that’s a sign that something has changed in the system. Now, it doesn’t mean it’s 100% a fuel problem. It could be mechanical. But it’s a sign that something needs to be looked at.

More Black Smoke Than Usual

A healthy running engine using good fuel will never produce black smoke – or blue or white smoke, for that matter.

Any time you see black smoke, it’s a sign that something is causing the fuel to burn incompletely.  There are numerous mechanical reasons for this – dirty injectors, a filter problem, bad EGR valve – but it can also very easily come from a fuel problem.  If the fuel is old and in the process of stratifying, it’s not going to burn cleanly.  The parts that don’t burn fully will come out as black smoke – soot particles from partially-burned fuel.

You can also get black smoke from fuel if there’s a microbe contamination of the fuel storage tank.  Microbes, like bacteria, mold and fungi, can quickly degrade the quality of fuel because of the acids and substances they excrete while feeding off the fuel.

A Change in Filter Behavior

Fuel filters function to keep particulate and contaminants out of the combustion chamber.   These filters have to be changed at certain intervals. If there’s a fuel problem, it can cause the fuel filter to “fill up” faster, necessitating filter changes at a greater interval. 

If you find yourself having to change filters more often than you typically do, that’s a strong indication that a fuel problem is present. In fact, it’s likely to be the strongest indication you can have.

Check out these other posts on fuel problems in cars:

• Is Running Your Car Low On Gas Bad for Your Fuel System?
• Solutions for gas tank treatment
• Check Engine Light. Ethanol Gas. Is there a connection?