Fuel Injector Service and MPG relationship

[sd300td]

Will changing, cleaning, rebuilding, etc. improve fuel economy?I know its been discussed here before, just couldn't locate a thread quickly.

I was signaled by a fellow motorist last night on the way home from work (w124 300D, looked like a later model 124), he asked me a bunch of questions while inching closer to the freeway signal. He also said that he drove the same car for a long time.

Asked me if it had a 3rd row seat, "no". He said "oh, do you wish it did", I said no.

He asked me about mpg. I said "about 21". He then said that when he got his injectors fixed/cleaned/replaced (not sure what he actually had done), that his mpg figures went up significantly.

I'm doubtful, but since I've done everything else, i.e. filters, valves, regular maintenance and no deferred maintenance whatsoever, it got me to thinking about injectors. I'm not sure how injectors could affect fuel economy, so I thought I'd ask you experts.

Thanks.

[Diesel911]

I don't know about expert; in all engines the more efficiently the fuel burns the better fuel economy you get.
The injectors effect the fuel economy because are supposed to atomize the fuel so that as much of it as possible combines with the oxygen in the air and burns. The better it burns the more power you get pre the amount of fuel you inject into the cylinder.
Also the better the fuel burns the less there is unburned to dilute your engine oil and less Soot created by the unburned fuel that also gets into the oil and aids in wearing out the parts.

Each Injector Spray Nozzle has a seating area that keeps the fuel in the nozzle until the fuel pressure is high enough to unseat the Spray Nozzle Pintel. When the Pintel unseats at the correct "Pop" pressure it atomizes well.
Fuel the leaks out of a worn seat before the "Pop" Pressure unseats the Pintel dose is not atomized like it is supposed to and creates incompletely burned fuel.

Besides the Pintel Seating area wearing out the "Pop" pressure tends to decrease over the years. High "Pop" pressures = better atomization of the fuel and better penetration into the combustion chamber. Meaning that the fuel will be burning in the part of the Combustion Chamber that it was designed to burn in.

[C Sean Watts]

It worked for me. Of course, the worse off your old injectors are, the more improvement you'll see.