Fuel Injectors vs. Fuel Mileage

Bigger injectors would equal more fuel, which means less fuel mileage or fuel economy, right? Not necessarily. That is what we are covering in this week’s article.

Two questions that we get on a regular basis are at opposite ends of the spectrum. Some think that larger fuel injectors will help to increase their fuel mileage because they read it on the internet, and then some think that more fuel will mean lower fuel mileage, which seems logical. Online, both claims are made and the short answer is that neither claim is necessarily wrong.

It can have either effect on your truck when upgrading injectors and it generally comes down to two different things, the condition of the injectors that are being removed and how heavy your right foot is with your newly found power. Which, as performance enthusiasts, we get it.

With larger injectors, tuning can be adjusted for the truck to run well and still get great fuel mileage. For example, having 175cc injectors does not mean that there is 175cc of diesel fuel being sprayed every time that the injectors are actuated. This is where injector pulse width or injector “on” time comes into play. There can be a larger injector, running less pulse width, that is actually spraying the same amount or even less overall fuel than a stock injector in certain scenarios, such as cruising down the highway. But if that is the case, can’t we just throw 300cc injectors in everything and get good fuel mileage? This is not something that I would suggest, as there is a balance. Tuning capabilities only go so far before they are limited by the mechanical abilities of the injector.

Typically, when there is a post online saying something like, “I installed 190cc injectors and gained 4 miles per gallon,” it is usually due to installing fresh injectors, and not due to the 190cc injector modification that is giving the fuel mileage gains. At the same time, there may be a post that says, “I installed 190cc injectors and lost 4 miles per gallon.” This is typically due to their right foot being a little heavier. We see it time and time again, when you have all of that newly found power, you tend to use it. It is fun after all, and exciting to smash the accelerator on a diesel pickup and watch the rear tires start to spin, going into a rolling burnout (Btw, never do this on a public road, it is intended for competition vehicles only). But, this is where all of that extra fuel that is now available is being used, and if that is done, even just a few times per tank of fuel, there will most likely be a noticeable drop in average mileage per gallon.

Most of our customers that have older, worn out injectors and who upgraded to something like our Premium Reman Power Stroke Injectors, do see an increase in fuel economy because of having injectors with all new parts, which means that the injectors are performing optimally and efficiently. If upgrading a set of good working condition injectors to a larger size, there’s not much room for fuel mileage improvement because the injectors are already running efficiently. So, as long as the gas pedal can be kept under control with the new power from the larger injectors, there will not be much of a change in average miles per gallon, if any at all.

The last common variable is the quality of injector that is being installed. Most companies do a core exchange and do not put new parts in them, they are simply modified and tested, so if you start with good working injectors and go to a larger injector, you could end up with someone else’s worn out injectors that have simply been modified to flow more fuel, but all of the other working parts are worn and not working as efficiently, so there will be a drop in fuel mileage. That is, again, why we only build from injectors supplied by the customer or from our Premium Remans with all new parts (See our other blog post “premiums vs. premiums vs. premiums”). That way, you know what you have or what you are getting.

In the end, do not upgrade to larger injectors in an attempt to get better fuel mileage, as new stock sized injectors will do the job if your current injectors are worn out. But at the same time, if you are looking for more power, do not be afraid to go to a larger injector because of losing fuel economy. With the appropriate tuning and driving habits you have nothing to worry about.

-Rykan