Is fuel economy an accurate measure of injector health?

[Crunch]

With 330K under their belt, my injectors are still working great. But like a 95 year old man I understand it is only a matter of time. It doesn't matter if that 95 year old man is Jack Lanne or a 4 pack a day smoker. But yesterday I had a driving trip that got me wondering.

I ran 519 miles, 1500lbs. (mostly water!) in the bed on the outbound side. The AC was blowing the whole way. I set the cruise at just under 70, keeping it there even when the speed limit was 75. My top speed was 90 MPH, which occurred briefly as I was passing someone and had to get back in the right lane before the passing lane disappeared in favor other traffic heading the other direction. Other than my truck being absolutely decimated by love bugs--literally thousands of their corpses now cover my truck, the trip was uneventful as far as anything that concerns the truck. I filled the tank just before I left, and the next refill was this morning after a good night's sleep. Fuel economy for the entire trip was 19.7 MPG. The engine ran perfectly smooth and I didn't see any visible smoke coming out of the exhaust the entire trip.

So can good fuel economy be construed to mean my injectors are not only working well, but still healthy? Is it just a happy coincidence? Or like so much else in life, is it not that simple?

 

[cerberusiam]

That means the pintle is seating correctly and the solenoids are still working correctly. As for internal wear and return orifices, that may not be so good and the injector will still work fine. I would guess they are probably a little noisy by now also.

 

[TCDiesel]

I just don't trust Injectors, with 330K miles or Kms? when there's any sign of problems after years of use , I would replace Them. its just to risky.

 

[Crunch]

That means the pintle is seating correctly and the solenoids are still working correctly. As for internal wear and return orifices, that may not be so good and the injector will still work fine. I would guess they are probably a little noisy by now also.

Maybe I'm lucky, but I haven't noticed any more noise than when the truck was new. On the other hand, maybe it's like the slowly boiling frog and I just haven't noticed. But I do a lot of long distance driving and tend to pay a lot of attention to truck sounds in general.

I just don't trust Injectors, with 330K miles or Kms? when there's any sign of problems after years of use , I would replace Them. its just to risky.

I agree, and know that it is just a matter of time. When that time comes I will definitely go with the new injectors. I can't stomach the idea of spending $50K on a new truck and having to live with the hassles of a cat and DEF, along with the reduced fuel economy that comes with it. Other than normal wear and tear from having a truck that doubles as a work truck and daily driver my truck is in very good shape. I think it could easily go another 10 years if I take care of it. Injectors and not crashing it would be the two biggest factors in doing that.

 

[Wayne M.]

Those are good numbers, especially pushing it to 90!
However, it's cheap insurance to change em out with quality replacements at this point.

 

[Tuesdak]

AC really hurts my MPG, however, your MPG looks really good. I range from 21MPG freeway AC off to 16 with AC on mixed driving. Fuel type, wind, grades, etc all make a difference. Unless you drive the same route every day you won't have a good MPG number and even then the fuel can be different.

You can test injectors and they be fine: till tomorrow when they fail. A real good factor is how long were the injectors run with better filtration? A bad tank of fuel can take them out. (and could also ruin older mechanical injectors.) Keep your fuel receipts - always. Your CC statement doesn't say gas or diesel and when they mix them up at the station etc...

 

[Crunch]

AC really hurts my MPG, however, your MPG looks really good. I range from 21MPG freeway AC off to 16 with AC on mixed driving. Fuel type, wind, grades, etc all make a difference. Unless you drive the same route every day you won't have a good MPG number and even then the fuel can be different.

You can test injectors and they be fine: till tomorrow when they fail. A real good factor is how long were the injectors run with better filtration? A bad tank of fuel can take them out. (and could also ruin older mechanical injectors.) Keep your fuel receipts - always. Your CC statement doesn't say gas or diesel and when they mix them up at the station etc...

That's interesting that you get noticeably lower fuel economy running the AC. I've never noticed a difference in fuel economy with the AC running. For me, it's either pulling a 12,000lb. trailer or getting above 2000 RPM's. Even when hauling with heavy loads in the bed the drop in MPG is minimal, as long as wind resistance isn't a factor. My truck is 2WD and completely stock, so maybe that makes a difference.

As for filtration, I've run the Fleetguard Stratapore for both oil and fuel filters since the first oil change. I change the fuel filter every 10,000 miles. I don't run any increased filtration, based on the constant run testing Cummins has done on the engines and the desire to maintain a constant fuel flow. I save all my fuel receipts, buy my fuel from either Love's (when on the road) or QT (when at home) whenever possible. I've never had a bad tank of fuel and have never seen a drop of water when draining the fuel filter canister. I also never experimented with home brew biodiesel, as was popular 10-15 years ago. But I am pretty religious about running 16oz. of Power Service through the tank every other fill up when on the road, less when at home. I seldom see smoke coming out of the exhaust, and when I do it's usually when passing someone while pulling a trailer, or when starting on a cold day. An engine tech at the local Cummins Southern Plains facility told me that they have seen engines with 500K mile on them, and the injectors are still good. I'm guessing that's very rare.